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Primary Gastrointestinal Lymphoma: Spectrum of Imaging Findings with Pathologic Correlation¹

¹ From the Departments of Medical Imaging (Sangeet G., J.P., Sandeep G.) and Histopathology (M.S.), University Hospital of North Staffordshire NHS Trust, Keele University, Stoke-on-Trent, England; and the Division of Abdominal Imaging, Department of Medical Imaging, University Health Network and Mount Sinai Hospital, University of Toronto, 585 University Ave, NCSB 1C544, Toronto, ON, Canada M5G 2N2 (Sangeet G., M.E.O., K.K.). Recipient of a Certificate of Merit award for an education exhibit at the 2005 RSNA Annual Meeting. Received August 11, 2006; revision requested November 9 and received December 15; accepted December 15. All authors have no financial relationships to disclose.

View larger version (83K): [in this window] [in a new window] [Download PPT slide]   Figure 1a.  B-cell type non-Hodgkin lymphoma of the esophagus in a 72-year-old woman who presented with dysphagia with solids. (a) Barium esophagogram shows a large polypoidal filling defect in the midesophagus with deep ulceration in the posterior wall (arrowheads). (b) Contrast material–enhanced computed tomographic (CT) scan obtained 3 weeks later shows fistulization with the trachea (arrow).

 

View larger version (84K): [in this window] [in a new window] [Download PPT slide]   Figure 1b.  B-cell type non-Hodgkin lymphoma of the esophagus in a 72-year-old woman who presented with dysphagia with solids. (a) Barium esophagogram shows a large polypoidal filling defect in the midesophagus with deep ulceration in the posterior wall (arrowheads). (b) Contrast material–enhanced computed tomographic (CT) scan obtained 3 weeks later shows fistulization with the trachea (arrow).

 

View larger version (124K): [in this window] [in a new window] [Download PPT slide]   Figure 2a.  Diffuse large B-cell lymphoma of the stomach in an 81-year-old man who presented with epigastric pain. (a) Spot radiograph from an upper gastrointestinal study shows a mass with luminal narrowing in the gastric antrum and deep ulceration in the inferior wall (arrow). Other nodules of various sizes (arrowhead) are seen adjacent to the mass. (b) Contrast-enhanced CT scan shows diffuse, homogeneous gastric antral wall thickening with a lobulated inner surface and a smooth well-defined outer wall (arrowheads). (c) High-power photomicrograph (original magnification, x600; hematoxylineosin [H-E] stain) shows a large blast cell infiltrate (short arrow) extending around epithelial glands (arrowhead). Mitoses, an important feature of high-grade tumors, are clearly seen (long arrow). (d) High-power photomicrograph (original magnification, x600; immunohistochemical stain CAM5.2) shows the destruction of epithelial glands by infiltrating blast cells (arrow). Brown areas represent cytokeratin.

 

View larger version (137K): [in this window] [in a new window] [Download PPT slide]   Figure 2b.  Diffuse large B-cell lymphoma of the stomach in an 81-year-old man who presented with epigastric pain. (a) Spot radiograph from an upper gastrointestinal study shows a mass with luminal narrowing in the gastric antrum and deep ulceration in the inferior wall (arrow). Other nodules of various sizes (arrowhead) are seen adjacent to the mass. (b) Contrast-enhanced CT scan shows diffuse, homogeneous gastric antral wall thickening with a lobulated inner surface and a smooth well-defined outer wall (arrowheads). (c) High-power photomicrograph (original magnification, x600; hematoxylineosin [H-E] stain) shows a large blast cell infiltrate (short arrow) extending around epithelial glands (arrowhead). Mitoses, an important feature of high-grade tumors, are clearly seen (long arrow). (d) High-power photomicrograph (original magnification, x600; immunohistochemical stain CAM5.2) shows the destruction of epithelial glands by infiltrating blast cells (arrow). Brown areas represent cytokeratin.

 

View larger version (150K): [in this window] [in a new window] [Download PPT slide]   Figure 2c.  Diffuse large B-cell lymphoma of the stomach in an 81-year-old man who presented with epigastric pain. (a) Spot radiograph from an upper gastrointestinal study shows a mass with luminal narrowing in the gastric antrum and deep ulceration in the inferior wall (arrow). Other nodules of various sizes (arrowhead) are seen adjacent to the mass. (b) Contrast-enhanced CT scan shows diffuse, homogeneous gastric antral wall thickening with a lobulated inner surface and a smooth well-defined outer wall (arrowheads). (c) High-power photomicrograph (original magnification, x600; hematoxylineosin [H-E] stain) shows a large blast cell infiltrate (short arrow) extending around epithelial glands (arrowhead). Mitoses, an important feature of high-grade tumors, are clearly seen (long arrow). (d) High-power photomicrograph (original magnification, x600; immunohistochemical stain CAM5.2) shows the destruction of epithelial glands by infiltrating blast cells (arrow). Brown areas represent cytokeratin.

 

View larger version (114K): [in this window] [in a new window] [Download PPT slide]   Figure 2d.  Diffuse large B-cell lymphoma of the stomach in an 81-year-old man who presented with epigastric pain. (a) Spot radiograph from an upper gastrointestinal study shows a mass with luminal narrowing in the gastric antrum and deep ulceration in the inferior wall (arrow). Other nodules of various sizes (arrowhead) are seen adjacent to the mass. (b) Contrast-enhanced CT scan shows diffuse, homogeneous gastric antral wall thickening with a lobulated inner surface and a smooth well-defined outer wall (arrowheads). (c) High-power photomicrograph (original magnification, x600; hematoxylineosin [H-E] stain) shows a large blast cell infiltrate (short arrow) extending around epithelial glands (arrowhead). Mitoses, an important feature of high-grade tumors, are clearly seen (long arrow). (d) High-power photomicrograph (original magnification, x600; immunohistochemical stain CAM5.2) shows the destruction of epithelial glands by infiltrating blast cells (arrow). Brown areas represent cytokeratin.

 

View larger version (122K): [in this window] [in a new window] [Download PPT slide]   Figure 3.  Diffuse large B-cell lymphoma of the stomach in a 50-year-old man with dyspepsia. Spot radiograph from a double-contrast upper gastrointestinal study shows a mass with nodular margins and luminal narrowing in the antrum of the stomach (arrowheads). Thickened nodular folds (arrow) are seen more proximally in the stomach. CT helped confirm antral thickening.

 

View larger version (151K): [in this window] [in a new window] [Download PPT slide]   Figure 4a.  Low-grade MALT lymphoma of the stomach in a 56-year-old woman who presented with dyspepsia. (a, b) Axial contrast-enhanced CT scan (a) and sagittal multiplanar reformatted image (b) show minimal thickening (arrowheads) in the antrum of the stomach (S). The rest of the stomach was normal. G = gallbladder. (c) Intermediate-power photomicrograph (original magnification, x100; H-E stain) of the gastric biopsy specimen shows an infiltrate of small blue lymphoid cells throughout, with very few gastric glands. (d) High-power photomicrograph (original magnification, x400; H-E stain) shows a lymphoepithelial lesion (arrow) formed by the infiltration of the gastric glands by groups of irregular small lymphoid cells. This finding is a classic feature of low-grade MALT lymphoma.

 

View larger version (149K): [in this window] [in a new window] [Download PPT slide]   Figure 4b.  Low-grade MALT lymphoma of the stomach in a 56-year-old woman who presented with dyspepsia. (a, b) Axial contrast-enhanced CT scan (a) and sagittal multiplanar reformatted image (b) show minimal thickening (arrowheads) in the antrum of the stomach (S). The rest of the stomach was normal. G = gallbladder. (c) Intermediate-power photomicrograph (original magnification, x100; H-E stain) of the gastric biopsy specimen shows an infiltrate of small blue lymphoid cells throughout, with very few gastric glands. (d) High-power photomicrograph (original magnification, x400; H-E stain) shows a lymphoepithelial lesion (arrow) formed by the infiltration of the gastric glands by groups of irregular small lymphoid cells. This finding is a classic feature of low-grade MALT lymphoma.

 

View larger version (168K): [in this window] [in a new window] [Download PPT slide]   Figure 4c.  Low-grade MALT lymphoma of the stomach in a 56-year-old woman who presented with dyspepsia. (a, b) Axial contrast-enhanced CT scan (a) and sagittal multiplanar reformatted image (b) show minimal thickening (arrowheads) in the antrum of the stomach (S). The rest of the stomach was normal. G = gallbladder. (c) Intermediate-power photomicrograph (original magnification, x100; H-E stain) of the gastric biopsy specimen shows an infiltrate of small blue lymphoid cells throughout, with very few gastric glands. (d) High-power photomicrograph (original magnification, x400; H-E stain) shows a lymphoepithelial lesion (arrow) formed by the infiltration of the gastric glands by groups of irregular small lymphoid cells. This finding is a classic feature of low-grade MALT lymphoma.

 

View larger version (161K): [in this window] [in a new window] [Download PPT slide]   Figure 4d.  Low-grade MALT lymphoma of the stomach in a 56-year-old woman who presented with dyspepsia. (a, b) Axial contrast-enhanced CT scan (a) and sagittal multiplanar reformatted image (b) show minimal thickening (arrowheads) in the antrum of the stomach (S). The rest of the stomach was normal. G = gallbladder. (c) Intermediate-power photomicrograph (original magnification, x100; H-E stain) of the gastric biopsy specimen shows an infiltrate of small blue lymphoid cells throughout, with very few gastric glands. (d) High-power photomicrograph (original magnification, x400; H-E stain) shows a lymphoepithelial lesion (arrow) formed by the infiltration of the gastric glands by groups of irregular small lymphoid cells. This finding is a classic feature of low-grade MALT lymphoma.

 

View larger version (137K): [in this window] [in a new window] [Download PPT slide]   Figure 5.  Diffuse large B-cell lymphoma of the stomach in a 70-year-old-man with anemia. Contrast-enhanced CT scan shows diffuse concentric thickening of the gastric wall involving the fundus and proximal body (arrowheads). Note that the perigastric fat planes are well maintained even though the tumor is very bulky. The suspected diagnosis of non-Hodgkin lymphoma, which was based on the imaging findings, was confirmed with biopsy, and the patient responded remarkably well to chemotherapy.

 

View larger version (131K): [in this window] [in a new window] [Download PPT slide]   Figure 6.  Diffuse large B-cell lymphoma of the stomach in a 59-year-old man with gastric outlet obstruction. Contrast-enhanced CT scan shows thickening of the antral wall with a nodular inner margin and a relatively smooth outer margin (arrowheads), along with distention of the stomach. There is mild stranding in the perigastric fat, with a few locoregional lymph nodes (arrow) and splenomegaly (S). It is uncommon for gastric lymphoma to manifest as gastric outlet obstruction.

 

View larger version (152K): [in this window] [in a new window] [Download PPT slide]   Figure 7.  Burkitt lymphoma in a 41-year-old woman who presented with abdominal pain and distention. Contrast-enhanced CT scan shows a markedly thickened small bowel loop (arrowheads) in the left side of the abdomen with aneurysmal dilatation. There is no evidence of obstruction.

 

View larger version (114K): [in this window] [in a new window] [Download PPT slide]   Figure 8a.  Burkitt lymphoma in a 7-year-old boy who presented with a 3-week history of vomiting, abdominal pain, and intermittent diarrhea. (a) Contrast-enhanced CT scan shows an ileocolic intussusception (arrowheads) with thickening of the terminal ileum. The hypoattenuating ileal mesenteric fat with mesenteric vessels extends into the cecal lumen (*). (b) Low-power photomicrograph (original magnification, x4; H-E stain) shows polypoid tumor invasion of the bowel wall (long arrow) through the muscle (short arrow). (c) High-power photomicrograph (original magnification, x600; H-E stain) shows a diffuse infiltrate of small to medium-sized blast cells, a finding that is typical of Burkitt lymphoma. Note that the blast cells are smaller than those shown in Figure 2c (diffuse large B-cell lymphoma). (d) High-power photomicrograph (original magnification, x600; immunohistochemical stain MIB1 for Ki 67, a cell cycle proliferation marker) shows proliferating cells, virtually all (>99%) of which are "in cycle" (ie, dividing), a typical finding in Burkitt lymphoma. The cells also stained positively with CD20, a marker for B cells.

 

View larger version (83K): [in this window] [in a new window] [Download PPT slide]   Figure 8b.  Burkitt lymphoma in a 7-year-old boy who presented with a 3-week history of vomiting, abdominal pain, and intermittent diarrhea. (a) Contrast-enhanced CT scan shows an ileocolic intussusception (arrowheads) with thickening of the terminal ileum. The hypoattenuating ileal mesenteric fat with mesenteric vessels extends into the cecal lumen (*). (b) Low-power photomicrograph (original magnification, x4; H-E stain) shows polypoid tumor invasion of the bowel wall (long arrow) through the muscle (short arrow). (c) High-power photomicrograph (original magnification, x600; H-E stain) shows a diffuse infiltrate of small to medium-sized blast cells, a finding that is typical of Burkitt lymphoma. Note that the blast cells are smaller than those shown in Figure 2c (diffuse large B-cell lymphoma). (d) High-power photomicrograph (original magnification, x600; immunohistochemical stain MIB1 for Ki 67, a cell cycle proliferation marker) shows proliferating cells, virtually all (>99%) of which are "in cycle" (ie, dividing), a typical finding in Burkitt lymphoma. The cells also stained positively with CD20, a marker for B cells.

 

View larger version (159K): [in this window] [in a new window] [Download PPT slide]   Figure 8c.  Burkitt lymphoma in a 7-year-old boy who presented with a 3-week history of vomiting, abdominal pain, and intermittent diarrhea. (a) Contrast-enhanced CT scan shows an ileocolic intussusception (arrowheads) with thickening of the terminal ileum. The hypoattenuating ileal mesenteric fat with mesenteric vessels extends into the cecal lumen (*). (b) Low-power photomicrograph (original magnification, x4; H-E stain) shows polypoid tumor invasion of the bowel wall (long arrow) through the muscle (short arrow). (c) High-power photomicrograph (original magnification, x600; H-E stain) shows a diffuse infiltrate of small to medium-sized blast cells, a finding that is typical of Burkitt lymphoma. Note that the blast cells are smaller than those shown in Figure 2c (diffuse large B-cell lymphoma). (d) High-power photomicrograph (original magnification, x600; immunohistochemical stain MIB1 for Ki 67, a cell cycle proliferation marker) shows proliferating cells, virtually all (>99%) of which are "in cycle" (ie, dividing), a typical finding in Burkitt lymphoma. The cells also stained positively with CD20, a marker for B cells.

 

View larger version (149K): [in this window] [in a new window] [Download PPT slide]   Figure 8d.  Burkitt lymphoma in a 7-year-old boy who presented with a 3-week history of vomiting, abdominal pain, and intermittent diarrhea. (a) Contrast-enhanced CT scan shows an ileocolic intussusception (arrowheads) with thickening of the terminal ileum. The hypoattenuating ileal mesenteric fat with mesenteric vessels extends into the cecal lumen (*). (b) Low-power photomicrograph (original magnification, x4; H-E stain) shows polypoid tumor invasion of the bowel wall (long arrow) through the muscle (short arrow). (c) High-power photomicrograph (original magnification, x600; H-E stain) shows a diffuse infiltrate of small to medium-sized blast cells, a finding that is typical of Burkitt lymphoma. Note that the blast cells are smaller than those shown in Figure 2c (diffuse large B-cell lymphoma). (d) High-power photomicrograph (original magnification, x600; immunohistochemical stain MIB1 for Ki 67, a cell cycle proliferation marker) shows proliferating cells, virtually all (>99%) of which are "in cycle" (ie, dividing), a typical finding in Burkitt lymphoma. The cells also stained positively with CD20, a marker for B cells.

 

View larger version (115K): [in this window] [in a new window] [Download PPT slide]   Figure 9.  High-grade large B-cell lymphoma of the small bowel in a 56-year-old man with bleeding from the rectum and anemia. Contrast-enhanced CT scan shows a markedly thickened terminal ileum (arrowheads) with a wall thickness of over 4 cm and no bowel obstruction.

 

View larger version (135K): [in this window] [in a new window] [Download PPT slide]   Figure 10a.  High-grade diffuse large B-cell lymphoma of the ileocecum in a 57-year-old man who presented with a 3-week history of right iliac fossa pain. (a) Contrast-enhanced CT scan obtained at the level of the right iliac fossa shows irregular thickening of the terminal ileum and the cecum with stranding in the adjacent mesentery. The posterior aspect of the ileocecal valve (arrow) is distended and thin compared with the anterior wall, although no definite perforation was identified at CT. Histologic analysis showed localized perforation at the site. (b) Contrast-enhanced CT scan obtained caudad to a shows concentric wall thickening of the terminal ileum (arrow) with stranding in the adjacent mesentery. Fluid-filled distended ileal loops (S) are also identified in the pelvis. (c) Low-power photomicrograph (original magnification, x4; H-E stain) shows infiltration of the bowel wall (short arrow) by tumor (long arrow).

 

View larger version (137K): [in this window] [in a new window] [Download PPT slide]   Figure 10b.  High-grade diffuse large B-cell lymphoma of the ileocecum in a 57-year-old man who presented with a 3-week history of right iliac fossa pain. (a) Contrast-enhanced CT scan obtained at the level of the right iliac fossa shows irregular thickening of the terminal ileum and the cecum with stranding in the adjacent mesentery. The posterior aspect of the ileocecal valve (arrow) is distended and thin compared with the anterior wall, although no definite perforation was identified at CT. Histologic analysis showed localized perforation at the site. (b) Contrast-enhanced CT scan obtained caudad to a shows concentric wall thickening of the terminal ileum (arrow) with stranding in the adjacent mesentery. Fluid-filled distended ileal loops (S) are also identified in the pelvis. (c) Low-power photomicrograph (original magnification, x4; H-E stain) shows infiltration of the bowel wall (short arrow) by tumor (long arrow).

 

View larger version (125K): [in this window] [in a new window] [Download PPT slide]   Figure 10c.  High-grade diffuse large B-cell lymphoma of the ileocecum in a 57-year-old man who presented with a 3-week history of right iliac fossa pain. (a) Contrast-enhanced CT scan obtained at the level of the right iliac fossa shows irregular thickening of the terminal ileum and the cecum with stranding in the adjacent mesentery. The posterior aspect of the ileocecal valve (arrow) is distended and thin compared with the anterior wall, although no definite perforation was identified at CT. Histologic analysis showed localized perforation at the site. (b) Contrast-enhanced CT scan obtained caudad to a shows concentric wall thickening of the terminal ileum (arrow) with stranding in the adjacent mesentery. Fluid-filled distended ileal loops (S) are also identified in the pelvis. (c) Low-power photomicrograph (original magnification, x4; H-E stain) shows infiltration of the bowel wall (short arrow) by tumor (long arrow).

 

View larger version (124K): [in this window] [in a new window] [Download PPT slide]   Figure 11a.  High-grade diffuse large B-cell lymphoma of the ileocecum with involvement of the appendix in a 33-year-old immunocompromised man who presented with bowel obstruction. The patient had undergone renal transplantation 6 years earlier. (a) Contrast-enhanced CT scan shows diffuse thickening of the terminal ileum and the cecum (arrowheads) with stranding in the adjacent mesentery and proximal small bowel obstruction. The transplanted kidney is seen in the left iliac fossa (K). Note the collapsed proximal sigmoid colon (arrow). (b) Contrast-enhanced CT scan obtained slightly caudad to a shows a thickened appendix (arrow). The suspected diagnosis of non-Hodgkin lymphoma, which was based on the imaging findings, was confirmed at histologic analysis.

 

View larger version (130K): [in this window] [in a new window] [Download PPT slide]   Figure 11b.  High-grade diffuse large B-cell lymphoma of the ileocecum with involvement of the appendix in a 33-year-old immunocompromised man who presented with bowel obstruction. The patient had undergone renal transplantation 6 years earlier. (a) Contrast-enhanced CT scan shows diffuse thickening of the terminal ileum and the cecum (arrowheads) with stranding in the adjacent mesentery and proximal small bowel obstruction. The transplanted kidney is seen in the left iliac fossa (K). Note the collapsed proximal sigmoid colon (arrow). (b) Contrast-enhanced CT scan obtained slightly caudad to a shows a thickened appendix (arrow). The suspected diagnosis of non-Hodgkin lymphoma, which was based on the imaging findings, was confirmed at histologic analysis.

 

View larger version (122K): [in this window] [in a new window] [Download PPT slide]   Figure 12a.  High-grade large B-cell lymphoma in a 68-year-old woman with weight loss and abdominal pain. (a) Spot radiograph from an upper gastrointestinal study shows an intrinsic duodenal mass with mucosal destruction and polypoidal filling defects (arrowheads). (b) Contrast-enhanced CT scan shows circumferential thickening of the duodenum with stranding in the adjacent mesentery and loss of fat plane with likely invasion into the head of the pancreas (P), a suspicion that was confirmed at histologic analysis.

 

View larger version (142K): [in this window] [in a new window] [Download PPT slide]   Figure 12b.  High-grade large B-cell lymphoma in a 68-year-old woman with weight loss and abdominal pain. (a) Spot radiograph from an upper gastrointestinal study shows an intrinsic duodenal mass with mucosal destruction and polypoidal filling defects (arrowheads). (b) Contrast-enhanced CT scan shows circumferential thickening of the duodenum with stranding in the adjacent mesentery and loss of fat plane with likely invasion into the head of the pancreas (P), a suspicion that was confirmed at histologic analysis.

 

View larger version (140K): [in this window] [in a new window] [Download PPT slide]   Figure 13a.  High-grade diffuse large B-cell lymphoma of the ileocecum in a 76-year-old man who presented with abdominal pain and fullness. (a) Contrast-enhanced CT scan obtained at the level of the right iliac fossa shows an ileocecal mass (arrowheads) without proximal obstruction. (b) Contrast-enhanced CT scan obtained superior to a shows diffuse omental and peritoneal lymphomatosis (arrowheads) with left paraaortic lymphadenopathy (A).

 

View larger version (135K): [in this window] [in a new window] [Download PPT slide]   Figure 13b.  High-grade diffuse large B-cell lymphoma of the ileocecum in a 76-year-old man who presented with abdominal pain and fullness. (a) Contrast-enhanced CT scan obtained at the level of the right iliac fossa shows an ileocecal mass (arrowheads) without proximal obstruction. (b) Contrast-enhanced CT scan obtained superior to a shows diffuse omental and peritoneal lymphomatosis (arrowheads) with left paraaortic lymphadenopathy (A).

 

View larger version (113K): [in this window] [in a new window] [Download PPT slide]   Figure 14a.  Diffuse large B-cell lymphoma of the duodenum in a 51-year-old man with upper gastrointestinal bleeding. The patient had undergone renal transplantation 8 years earlier. (a) Abdominal US image through the long axis of the duodenum (D) shows markedly hypoechoic wall thickening. AO = aorta, IVC = inferior vena cava, SMA = superior mesenteric artery, SMV = superior mesenteric vein. (b) Corresponding unenhanced CT scan shows thickening of the third and fourth portions of the duodenum (D).

 

View larger version (133K): [in this window] [in a new window] [Download PPT slide]   Figure 14b.  Diffuse large B-cell lymphoma of the duodenum in a 51-year-old man with upper gastrointestinal bleeding. The patient had undergone renal transplantation 8 years earlier. (a) Abdominal US image through the long axis of the duodenum (D) shows markedly hypoechoic wall thickening. AO = aorta, IVC = inferior vena cava, SMA = superior mesenteric artery, SMV = superior mesenteric vein. (b) Corresponding unenhanced CT scan shows thickening of the third and fourth portions of the duodenum (D).

 

View larger version (127K): [in this window] [in a new window] [Download PPT slide]   Figure 15a.  Primary fusion lymphoma involving the large intestine in a 59-year-old man with HIV infection who presented with abdominal pain and bloody stools. (a) Pelvic US image through the short axis of the large intestine shows asymmetric bowel wall thickening (arrowheads). L = lumen. (b) Contrast-enhanced CT scan shows that the tumor (arrowheads) involves the sigmoid colon. Arrow indicates ascites.

 

View larger version (132K): [in this window] [in a new window] [Download PPT slide]   Figure 15b.  Primary fusion lymphoma involving the large intestine in a 59-year-old man with HIV infection who presented with abdominal pain and bloody stools. (a) Pelvic US image through the short axis of the large intestine shows asymmetric bowel wall thickening (arrowheads). L = lumen. (b) Contrast-enhanced CT scan shows that the tumor (arrowheads) involves the sigmoid colon. Arrow indicates ascites.

 

View larger version (123K): [in this window] [in a new window] [Download PPT slide]   Figure 16a.  Diffuse large B-cell lymphoma in a 43-year-old man with HIV infection. The patient was admitted to the hospital with a history of weight loss, abdominal pain, diarrhea, and an abdominal mass. (a) Long-axis US image shows an ileocecal intussusception. The echogenic mesenteric fat is seen trapped between the intussusceptum (i) and the intussuscipiens (o). (b) Corresponding contrast-enhanced CT scan shows the ileocolic intussusception (arrowheads) in the midabdomen. The eccentric hypoattenuating mesenteric fat (*) is identified within the cecal lumen.

 

View larger version (118K): [in this window] [in a new window] [Download PPT slide]   Figure 16b.  Diffuse large B-cell lymphoma in a 43-year-old man with HIV infection. The patient was admitted to the hospital with a history of weight loss, abdominal pain, diarrhea, and an abdominal mass. (a) Long-axis US image shows an ileocecal intussusception. The echogenic mesenteric fat is seen trapped between the intussusceptum (i) and the intussuscipiens (o). (b) Corresponding contrast-enhanced CT scan shows the ileocolic intussusception (arrowheads) in the midabdomen. The eccentric hypoattenuating mesenteric fat (*) is identified within the cecal lumen.

 

View larger version (126K): [in this window] [in a new window] [Download PPT slide]   Figure 17a.  Enteropathy type T-cell lymphoma in a 36-year-old man with a history of celiac disease who presented with abdominal pain, weight loss, diarrhea, and spiking temperature. (a) Image from a barium meal follow-through study shows an abnormal small bowel loop (arrowheads) in the midabdomen with aneurysmal dilatation, fold thickening, and ulceration. (b) Contrast-enhanced CT scan shows thickened distal jejunal loops in the left side of the abdomen with stranding in the adjacent mesentery. There is a suggestion of ulceration in the thickened wall of one of the jejunal loops (arrow). Contrast material has not been retained in the affected loops but is present in the normal-appearing more distal ileal loops (arrowheads). A few prominent locoregional lymph nodes are identified in the jejunal mesentery. (c) High-power photomicrograph (original magnification, x600; H-E stain) shows very large pleomorphic cells, some of which have horseshoe-shaped nuclei (arrow). (d) On a high-power photomicrograph (original magnification, x600; immunostain CD20), the tumor cells are negative (ie, are not stained brown) (arrow) and thus are not B cells. (e) High-power photomicrograph (original magnification, x400; immunostain CD3) shows the pleomorphic T cells (arrow) marked with the T-cell marker CD3. (f) Low-power photomicrograph (original magnification, x40; H-E stain) shows some blunting of the villous architecture but not complete flattening as would be seen in untreated celiac disease; instead, these findings are consistent with partially treated celiac disease. An increase in intraepithelial lymphocytes, a finding that is also typical of celiac disease, was seen at high-power microscopy.

 

View larger version (142K): [in this window] [in a new window] [Download PPT slide]   Figure 17b.  Enteropathy type T-cell lymphoma in a 36-year-old man with a history of celiac disease who presented with abdominal pain, weight loss, diarrhea, and spiking temperature. (a) Image from a barium meal follow-through study shows an abnormal small bowel loop (arrowheads) in the midabdomen with aneurysmal dilatation, fold thickening, and ulceration. (b) Contrast-enhanced CT scan shows thickened distal jejunal loops in the left side of the abdomen with stranding in the adjacent mesentery. There is a suggestion of ulceration in the thickened wall of one of the jejunal loops (arrow). Contrast material has not been retained in the affected loops but is present in the normal-appearing more distal ileal loops (arrowheads). A few prominent locoregional lymph nodes are identified in the jejunal mesentery. (c) High-power photomicrograph (original magnification, x600; H-E stain) shows very large pleomorphic cells, some of which have horseshoe-shaped nuclei (arrow). (d) On a high-power photomicrograph (original magnification, x600; immunostain CD20), the tumor cells are negative (ie, are not stained brown) (arrow) and thus are not B cells. (e) High-power photomicrograph (original magnification, x400; immunostain CD3) shows the pleomorphic T cells (arrow) marked with the T-cell marker CD3. (f) Low-power photomicrograph (original magnification, x40; H-E stain) shows some blunting of the villous architecture but not complete flattening as would be seen in untreated celiac disease; instead, these findings are consistent with partially treated celiac disease. An increase in intraepithelial lymphocytes, a finding that is also typical of celiac disease, was seen at high-power microscopy.

 

View larger version (144K): [in this window] [in a new window] [Download PPT slide]   Figure 17c.  Enteropathy type T-cell lymphoma in a 36-year-old man with a history of celiac disease who presented with abdominal pain, weight loss, diarrhea, and spiking temperature. (a) Image from a barium meal follow-through study shows an abnormal small bowel loop (arrowheads) in the midabdomen with aneurysmal dilatation, fold thickening, and ulceration. (b) Contrast-enhanced CT scan shows thickened distal jejunal loops in the left side of the abdomen with stranding in the adjacent mesentery. There is a suggestion of ulceration in the thickened wall of one of the jejunal loops (arrow). Contrast material has not been retained in the affected loops but is present in the normal-appearing more distal ileal loops (arrowheads). A few prominent locoregional lymph nodes are identified in the jejunal mesentery. (c) High-power photomicrograph (original magnification, x600; H-E stain) shows very large pleomorphic cells, some of which have horseshoe-shaped nuclei (arrow). (d) On a high-power photomicrograph (original magnification, x600; immunostain CD20), the tumor cells are negative (ie, are not stained brown) (arrow) and thus are not B cells. (e) High-power photomicrograph (original magnification, x400; immunostain CD3) shows the pleomorphic T cells (arrow) marked with the T-cell marker CD3. (f) Low-power photomicrograph (original magnification, x40; H-E stain) shows some blunting of the villous architecture but not complete flattening as would be seen in untreated celiac disease; instead, these findings are consistent with partially treated celiac disease. An increase in intraepithelial lymphocytes, a finding that is also typical of celiac disease, was seen at high-power microscopy.

 

View larger version (138K): [in this window] [in a new window] [Download PPT slide]   Figure 17d.  Enteropathy type T-cell lymphoma in a 36-year-old man with a history of celiac disease who presented with abdominal pain, weight loss, diarrhea, and spiking temperature. (a) Image from a barium meal follow-through study shows an abnormal small bowel loop (arrowheads) in the midabdomen with aneurysmal dilatation, fold thickening, and ulceration. (b) Contrast-enhanced CT scan shows thickened distal jejunal loops in the left side of the abdomen with stranding in the adjacent mesentery. There is a suggestion of ulceration in the thickened wall of one of the jejunal loops (arrow). Contrast material has not been retained in the affected loops but is present in the normal-appearing more distal ileal loops (arrowheads). A few prominent locoregional lymph nodes are identified in the jejunal mesentery. (c) High-power photomicrograph (original magnification, x600; H-E stain) shows very large pleomorphic cells, some of which have horseshoe-shaped nuclei (arrow). (d) On a high-power photomicrograph (original magnification, x600; immunostain CD20), the tumor cells are negative (ie, are not stained brown) (arrow) and thus are not B cells. (e) High-power photomicrograph (original magnification, x400; immunostain CD3) shows the pleomorphic T cells (arrow) marked with the T-cell marker CD3. (f) Low-power photomicrograph (original magnification, x40; H-E stain) shows some blunting of the villous architecture but not complete flattening as would be seen in untreated celiac disease; instead, these findings are consistent with partially treated celiac disease. An increase in intraepithelial lymphocytes, a finding that is also typical of celiac disease, was seen at high-power microscopy.

 

View larger version (133K): [in this window] [in a new window] [Download PPT slide]   Figure 17e.  Enteropathy type T-cell lymphoma in a 36-year-old man with a history of celiac disease who presented with abdominal pain, weight loss, diarrhea, and spiking temperature. (a) Image from a barium meal follow-through study shows an abnormal small bowel loop (arrowheads) in the midabdomen with aneurysmal dilatation, fold thickening, and ulceration. (b) Contrast-enhanced CT scan shows thickened distal jejunal loops in the left side of the abdomen with stranding in the adjacent mesentery. There is a suggestion of ulceration in the thickened wall of one of the jejunal loops (arrow). Contrast material has not been retained in the affected loops but is present in the normal-appearing more distal ileal loops (arrowheads). A few prominent locoregional lymph nodes are identified in the jejunal mesentery. (c) High-power photomicrograph (original magnification, x600; H-E stain) shows very large pleomorphic cells, some of which have horseshoe-shaped nuclei (arrow). (d) On a high-power photomicrograph (original magnification, x600; immunostain CD20), the tumor cells are negative (ie, are not stained brown) (arrow) and thus are not B cells. (e) High-power photomicrograph (original magnification, x400; immunostain CD3) shows the pleomorphic T cells (arrow) marked with the T-cell marker CD3. (f) Low-power photomicrograph (original magnification, x40; H-E stain) shows some blunting of the villous architecture but not complete flattening as would be seen in untreated celiac disease; instead, these findings are consistent with partially treated celiac disease. An increase in intraepithelial lymphocytes, a finding that is also typical of celiac disease, was seen at high-power microscopy.

 

View larger version (82K): [in this window] [in a new window] [Download PPT slide]   Figure 17f.  Enteropathy type T-cell lymphoma in a 36-year-old man with a history of celiac disease who presented with abdominal pain, weight loss, diarrhea, and spiking temperature. (a) Image from a barium meal follow-through study shows an abnormal small bowel loop (arrowheads) in the midabdomen with aneurysmal dilatation, fold thickening, and ulceration. (b) Contrast-enhanced CT scan shows thickened distal jejunal loops in the left side of the abdomen with stranding in the adjacent mesentery. There is a suggestion of ulceration in the thickened wall of one of the jejunal loops (arrow). Contrast material has not been retained in the affected loops but is present in the normal-appearing more distal ileal loops (arrowheads). A few prominent locoregional lymph nodes are identified in the jejunal mesentery. (c) High-power photomicrograph (original magnification, x600; H-E stain) shows very large pleomorphic cells, some of which have horseshoe-shaped nuclei (arrow). (d) On a high-power photomicrograph (original magnification, x600; immunostain CD20), the tumor cells are negative (ie, are not stained brown) (arrow) and thus are not B cells. (e) High-power photomicrograph (original magnification, x400; immunostain CD3) shows the pleomorphic T cells (arrow) marked with the T-cell marker CD3. (f) Low-power photomicrograph (original magnification, x40; H-E stain) shows some blunting of the villous architecture but not complete flattening as would be seen in untreated celiac disease; instead, these findings are consistent with partially treated celiac disease. An increase in intraepithelial lymphocytes, a finding that is also typical of celiac disease, was seen at high-power microscopy.

 

View larger version (137K): [in this window] [in a new window] [Download PPT slide]   Figure 18a.  Nonenteropathic type T/NK–large cell lymphoma in a 61-year-old man who presented with recurrent episodes of peritonitis and bowel perforation. (a) Contrast-enhanced CT scan shows a duodenal mass with localized perforation along the medial wall (arrow). An adjacent enlarged peripancreatic lymph node is also present (*). (b) CT scan obtained 8 months after initial presentation shows localized cecal perforation anteriorly (P). On this occasion, the patient had presented with another episode of acute abdominal pain.

 

View larger version (129K): [in this window] [in a new window] [Download PPT slide]   Figure 18b.  Nonenteropathic type T/NK–large cell lymphoma in a 61-year-old man who presented with recurrent episodes of peritonitis and bowel perforation. (a) Contrast-enhanced CT scan shows a duodenal mass with localized perforation along the medial wall (arrow). An adjacent enlarged peripancreatic lymph node is also present (*). (b) CT scan obtained 8 months after initial presentation shows localized cecal perforation anteriorly (P). On this occasion, the patient had presented with another episode of acute abdominal pain.

 

View larger version (137K): [in this window] [in a new window] [Download PPT slide]   Figure 19a.  Low-grade B-cell lymphoma of the cecum in a 58-year-old man with pain in the right iliac fossa. Contrast-enhanced CT scans show thickening with a soft-tissue mass involving the ileocecal junction (arrow in a) and the cecum (M), with coning of the tip of the mass (arrow in b). Small bowel loops are normal in caliber. These findings mimic those in tuberculosis and amebiasis.

 

View larger version (146K): [in this window] [in a new window] [Download PPT slide]   Figure 19b.  Low-grade B-cell lymphoma of the cecum in a 58-year-old man with pain in the right iliac fossa. Contrast-enhanced CT scans show thickening with a soft-tissue mass involving the ileocecal junction (arrow in a) and the cecum (M), with coning of the tip of the mass (arrow in b). Small bowel loops are normal in caliber. These findings mimic those in tuberculosis and amebiasis.

 

View larger version (111K): [in this window] [in a new window] [Download PPT slide]   Figure 20.  Kaposi sarcoma mimicking acquired immunodeficiency syndrome (AIDS)–related lymphoma in a 23-year-old man with HIV infection who was admitted to the hospital with weight loss, fatigue, and anorexia. Contrast-enhanced CT scan shows a polypoid cecal mass (arrow). Biopsy of the mass showed proliferating spindle cells infiltrating the lamina propria, a finding that is consistent with Kaposi sarcoma. Distinguishing between AIDS-related lymphoma and Kaposi sarcoma at imaging may be very difficult, although the growth pattern of Kaposi sarcoma is more focal and nodular.

 

View larger version (127K): [in this window] [in a new window] [Download PPT slide]   Figure 21a.  Extranodal primary marginal zone MALT lymphoma of the rectum with infiltration to the posterior vaginal wall in a 69-year-old woman. (a) Contrast-enhanced CT scan shows a bulky nodular upper rectal mass (M) that arises from the anterior wall and extends into the anterior perirectal fat. The posterior rectal wall appears to be free of involvement by the mass. (b) Axial spin-echo T1-weighted MR image shows a hypointense mass (M) that arises from the anterior wall of the upper rectum and extends anteriorly to the mesorectal fascia (arrowheads). (c) On an axial fast spin-echo T2-weighted MR image, the large rectal mass (M) extends anteriorly within the perirectal fat to involve the mesorectal fascia. A small area of necrosis is identified within the mass (arrow). The mass also abuts the vaginal vault (V). Histopathologic analysis showed tumor invasion into the adherent vaginal wall. No enlarged perirectal-locoregional lymph nodes were identified. (d) Photograph of the resected specimen shows a large rectal mass with perirectal extension. A = anus. (e) Photograph of cut sections of the resected specimen shows a pale polypoid tumor (M) that arises from the anterior wall and occludes much of the lumen. (f) Low-power photomicrograph (original magnification, x4; H-E stain) shows erosion of the tumor (short arrow) through the mucosa and muscularis propria (long arrow). (g) High-power photomicrograph (original magnification, x400; H-E stain) shows a diffuse, dense monomorphic infiltrate of small lymphoid cells forming a low-grade small cell lymphoma, a finding that is consistent with MALT lymphoma. (h) Intermediate-power photomicrograph (original magnification, x100; immunostain CD21) shows stained follicular dendritic cells, which normally represent the germinal centers. In this case, the cells are disrupted (arrow) due to destruction by tumor. This finding is a feature of MALT lymphoma, in which reactive follicles are formed in an area of chronic inflammation. If a lymphoma develops, it destroys these follicles.

 

View larger version (142K): [in this window] [in a new window] [Download PPT slide]   Figure 21b.  Extranodal primary marginal zone MALT lymphoma of the rectum with infiltration to the posterior vaginal wall in a 69-year-old woman. (a) Contrast-enhanced CT scan shows a bulky nodular upper rectal mass (M) that arises from the anterior wall and extends into the anterior perirectal fat. The posterior rectal wall appears to be free of involvement by the mass. (b) Axial spin-echo T1-weighted MR image shows a hypointense mass (M) that arises from the anterior wall of the upper rectum and extends anteriorly to the mesorectal fascia (arrowheads). (c) On an axial fast spin-echo T2-weighted MR image, the large rectal mass (M) extends anteriorly within the perirectal fat to involve the mesorectal fascia. A small area of necrosis is identified within the mass (arrow). The mass also abuts the vaginal vault (V). Histopathologic analysis showed tumor invasion into the adherent vaginal wall. No enlarged perirectal-locoregional lymph nodes were identified. (d) Photograph of the resected specimen shows a large rectal mass with perirectal extension. A = anus. (e) Photograph of cut sections of the resected specimen shows a pale polypoid tumor (M) that arises from the anterior wall and occludes much of the lumen. (f) Low-power photomicrograph (original magnification, x4; H-E stain) shows erosion of the tumor (short arrow) through the mucosa and muscularis propria (long arrow). (g) High-power photomicrograph (original magnification, x400; H-E stain) shows a diffuse, dense monomorphic infiltrate of small lymphoid cells forming a low-grade small cell lymphoma, a finding that is consistent with MALT lymphoma. (h) Intermediate-power photomicrograph (original magnification, x100; immunostain CD21) shows stained follicular dendritic cells, which normally represent the germinal centers. In this case, the cells are disrupted (arrow) due to destruction by tumor. This finding is a feature of MALT lymphoma, in which reactive follicles are formed in an area of chronic inflammation. If a lymphoma develops, it destroys these follicles.

 

View larger version (131K): [in this window] [in a new window] [Download PPT slide]   Figure 21c.  Extranodal primary marginal zone MALT lymphoma of the rectum with infiltration to the posterior vaginal wall in a 69-year-old woman. (a) Contrast-enhanced CT scan shows a bulky nodular upper rectal mass (M) that arises from the anterior wall and extends into the anterior perirectal fat. The posterior rectal wall appears to be free of involvement by the mass. (b) Axial spin-echo T1-weighted MR image shows a hypointense mass (M) that arises from the anterior wall of the upper rectum and extends anteriorly to the mesorectal fascia (arrowheads). (c) On an axial fast spin-echo T2-weighted MR image, the large rectal mass (M) extends anteriorly within the perirectal fat to involve the mesorectal fascia. A small area of necrosis is identified within the mass (arrow). The mass also abuts the vaginal vault (V). Histopathologic analysis showed tumor invasion into the adherent vaginal wall. No enlarged perirectal-locoregional lymph nodes were identified. (d) Photograph of the resected specimen shows a large rectal mass with perirectal extension. A = anus. (e) Photograph of cut sections of the resected specimen shows a pale polypoid tumor (M) that arises from the anterior wall and occludes much of the lumen. (f) Low-power photomicrograph (original magnification, x4; H-E stain) shows erosion of the tumor (short arrow) through the mucosa and muscularis propria (long arrow). (g) High-power photomicrograph (original magnification, x400; H-E stain) shows a diffuse, dense monomorphic infiltrate of small lymphoid cells forming a low-grade small cell lymphoma, a finding that is consistent with MALT lymphoma. (h) Intermediate-power photomicrograph (original magnification, x100; immunostain CD21) shows stained follicular dendritic cells, which normally represent the germinal centers. In this case, the cells are disrupted (arrow) due to destruction by tumor. This finding is a feature of MALT lymphoma, in which reactive follicles are formed in an area of chronic inflammation. If a lymphoma develops, it destroys these follicles.

 

View larger version (140K): [in this window] [in a new window] [Download PPT slide]   Figure 21d.  Extranodal primary marginal zone MALT lymphoma of the rectum with infiltration to the posterior vaginal wall in a 69-year-old woman. (a) Contrast-enhanced CT scan shows a bulky nodular upper rectal mass (M) that arises from the anterior wall and extends into the anterior perirectal fat. The posterior rectal wall appears to be free of involvement by the mass. (b) Axial spin-echo T1-weighted MR image shows a hypointense mass (M) that arises from the anterior wall of the upper rectum and extends anteriorly to the mesorectal fascia (arrowheads). (c) On an axial fast spin-echo T2-weighted MR image, the large rectal mass (M) extends anteriorly within the perirectal fat to involve the mesorectal fascia. A small area of necrosis is identified within the mass (arrow). The mass also abuts the vaginal vault (V). Histopathologic analysis showed tumor invasion into the adherent vaginal wall. No enlarged perirectal-locoregional lymph nodes were identified. (d) Photograph of the resected specimen shows a large rectal mass with perirectal extension. A = anus. (e) Photograph of cut sections of the resected specimen shows a pale polypoid tumor (M) that arises from the anterior wall and occludes much of the lumen. (f) Low-power photomicrograph (original magnification, x4; H-E stain) shows erosion of the tumor (short arrow) through the mucosa and muscularis propria (long arrow). (g) High-power photomicrograph (original magnification, x400; H-E stain) shows a diffuse, dense monomorphic infiltrate of small lymphoid cells forming a low-grade small cell lymphoma, a finding that is consistent with MALT lymphoma. (h) Intermediate-power photomicrograph (original magnification, x100; immunostain CD21) shows stained follicular dendritic cells, which normally represent the germinal centers. In this case, the cells are disrupted (arrow) due to destruction by tumor. This finding is a feature of MALT lymphoma, in which reactive follicles are formed in an area of chronic inflammation. If a lymphoma develops, it destroys these follicles.

 

View larger version (131K): [in this window] [in a new window] [Download PPT slide]   Figure 21e.  Extranodal primary marginal zone MALT lymphoma of the rectum with infiltration to the posterior vaginal wall in a 69-year-old woman. (a) Contrast-enhanced CT scan shows a bulky nodular upper rectal mass (M) that arises from the anterior wall and extends into the anterior perirectal fat. The posterior rectal wall appears to be free of involvement by the mass. (b) Axial spin-echo T1-weighted MR image shows a hypointense mass (M) that arises from the anterior wall of the upper rectum and extends anteriorly to the mesorectal fascia (arrowheads). (c) On an axial fast spin-echo T2-weighted MR image, the large rectal mass (M) extends anteriorly within the perirectal fat to involve the mesorectal fascia. A small area of necrosis is identified within the mass (arrow). The mass also abuts the vaginal vault (V). Histopathologic analysis showed tumor invasion into the adherent vaginal wall. No enlarged perirectal-locoregional lymph nodes were identified. (d) Photograph of the resected specimen shows a large rectal mass with perirectal extension. A = anus. (e) Photograph of cut sections of the resected specimen shows a pale polypoid tumor (M) that arises from the anterior wall and occludes much of the lumen. (f) Low-power photomicrograph (original magnification, x4; H-E stain) shows erosion of the tumor (short arrow) through the mucosa and muscularis propria (long arrow). (g) High-power photomicrograph (original magnification, x400; H-E stain) shows a diffuse, dense monomorphic infiltrate of small lymphoid cells forming a low-grade small cell lymphoma, a finding that is consistent with MALT lymphoma. (h) Intermediate-power photomicrograph (original magnification, x100; immunostain CD21) shows stained follicular dendritic cells, which normally represent the germinal centers. In this case, the cells are disrupted (arrow) due to destruction by tumor. This finding is a feature of MALT lymphoma, in which reactive follicles are formed in an area of chronic inflammation. If a lymphoma develops, it destroys these follicles.

 

View larger version (109K): [in this window] [in a new window] [Download PPT slide]   Figure 21f.  Extranodal primary marginal zone MALT lymphoma of the rectum with infiltration to the posterior vaginal wall in a 69-year-old woman. (a) Contrast-enhanced CT scan shows a bulky nodular upper rectal mass (M) that arises from the anterior wall and extends into the anterior perirectal fat. The posterior rectal wall appears to be free of involvement by the mass. (b) Axial spin-echo T1-weighted MR image shows a hypointense mass (M) that arises from the anterior wall of the upper rectum and extends anteriorly to the mesorectal fascia (arrowheads). (c) On an axial fast spin-echo T2-weighted MR image, the large rectal mass (M) extends anteriorly within the perirectal fat to involve the mesorectal fascia. A small area of necrosis is identified within the mass (arrow). The mass also abuts the vaginal vault (V). Histopathologic analysis showed tumor invasion into the adherent vaginal wall. No enlarged perirectal-locoregional lymph nodes were identified. (d) Photograph of the resected specimen shows a large rectal mass with perirectal extension. A = anus. (e) Photograph of cut sections of the resected specimen shows a pale polypoid tumor (M) that arises from the anterior wall and occludes much of the lumen. (f) Low-power photomicrograph (original magnification, x4; H-E stain) shows erosion of the tumor (short arrow) through the mucosa and muscularis propria (long arrow). (g) High-power photomicrograph (original magnification, x400; H-E stain) shows a diffuse, dense monomorphic infiltrate of small lymphoid cells forming a low-grade small cell lymphoma, a finding that is consistent with MALT lymphoma. (h) Intermediate-power photomicrograph (original magnification, x100; immunostain CD21) shows stained follicular dendritic cells, which normally represent the germinal centers. In this case, the cells are disrupted (arrow) due to destruction by tumor. This finding is a feature of MALT lymphoma, in which reactive follicles are formed in an area of chronic inflammation. If a lymphoma develops, it destroys these follicles.

 

View larger version (172K): [in this window] [in a new window] [Download PPT slide]   Figure 21g.  Extranodal primary marginal zone MALT lymphoma of the rectum with infiltration to the posterior vaginal wall in a 69-year-old woman. (a) Contrast-enhanced CT scan shows a bulky nodular upper rectal mass (M) that arises from the anterior wall and extends into the anterior perirectal fat. The posterior rectal wall appears to be free of involvement by the mass. (b) Axial spin-echo T1-weighted MR image shows a hypointense mass (M) that arises from the anterior wall of the upper rectum and extends anteriorly to the mesorectal fascia (arrowheads). (c) On an axial fast spin-echo T2-weighted MR image, the large rectal mass (M) extends anteriorly within the perirectal fat to involve the mesorectal fascia. A small area of necrosis is identified within the mass (arrow). The mass also abuts the vaginal vault (V). Histopathologic analysis showed tumor invasion into the adherent vaginal wall. No enlarged perirectal-locoregional lymph nodes were identified. (d) Photograph of the resected specimen shows a large rectal mass with perirectal extension. A = anus. (e) Photograph of cut sections of the resected specimen shows a pale polypoid tumor (M) that arises from the anterior wall and occludes much of the lumen. (f) Low-power photomicrograph (original magnification, x4; H-E stain) shows erosion of the tumor (short arrow) through the mucosa and muscularis propria (long arrow). (g) High-power photomicrograph (original magnification, x400; H-E stain) shows a diffuse, dense monomorphic infiltrate of small lymphoid cells forming a low-grade small cell lymphoma, a finding that is consistent with MALT lymphoma. (h) Intermediate-power