DOI: 10.1148/rg.272065134
RadioGraphics 2007;27:553-557
© RSNA, 2007
Best Cases from the AFIP
Giant Mucinous Cystadenoma of the Appendix1
Thara Persaud, MB,
Niall Swan, MB and
William C. Torreggiani, MB
1 From the Department of Radiology, Adelaide and Meath Incorporating the National Children’s Hospital, Tallaght, Dublin 24, Ireland. Received July 13, 2006; revision requested August 16 and received September 26; accepted September 29. All authors have no financial relationships to disclose.
Address correspondence to W.C.T. (e-mail: william.torreggiani{at}amnch.ie).
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History
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An 80-year-old woman presented to the emergency department with a 5-day history of a swollen left calf that was confirmed to be secondary to deep vein thrombosis at Doppler ultrasonographic (US) evaluation. The findings were unremarkable, apart from a 3-cm difference in circumference between the right and left calves. She was otherwise well and had no known risk factors for deep vein thrombosis. As part of her work-up, the patient underwent imaging of the pelvis with contrast material–enhanced computed tomography (CT). The CT scan demonstrated a pelvic mass in the region of the appendix. Subsequently, magnetic resonance (MR) imaging was performed to further evaluate this lesion.
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Imaging Findings
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A left lower limb Doppler US examination established the presence of an extensive thrombus within the lumen of the left femoral vein.
CT of the pelvis was performed by using a helical CT system (Xpress/GS 1S; Toshiba, Tokyo, Japan). Imaging was carried out 1 hour after oral administration of 20 mL of gastrografin diluted in 1 L of water. First, an intravenous injection of 100 mL of contrast material was administered at a rate of 2.5 mL/sec; scanning was then performed after a delay of 60 seconds. CT images demonstrated a large tubular mass that extended across the pelvis (Fig 1). The length of the mass on CT images was 17 cm, and its diameter was 6 cm. The center of the mass appeared to have fluid attenuation, and the walls of the mass contained calcifications. The mass was seen to extend from the cecum at the expected location of the appendix. The cecum was normal in appearance; however, no normal appendix was identified. The mass lay anterior to the uterus and was clearly separate from this structure. In the left side of the pelvis, the tip of the mass was seen to compress the left external iliac vein, and a thrombus was identified in the distal lumen of the vessel. No ascites or pelvic or retroperitoneal lymphadenopathy was present.
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Figure 1. Axial pelvic CT scan obtained with both oral and intravenous contrast agents depicts a 17-cm tubular mass that extends across the pelvis and that contains a central area of cystic change and peripheral wall calcifications. The mass is attached to the cecum on the right side and, on the left, compresses the left external iliac vein.
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At MR imaging of the pelvis the mass was confirmed to be predominantly cystic, with low signal intensity on T1-weighted images and uniformly high signal intensity at its center on T2-weighted images. A clear connection between the mass and the cecum was demonstrated. The walls of the mass were thickened and had signal intensity suggestive of calcification. On the left side, the mass was again seen to compress the left external iliac vein, which contained a region of high signal intensity indicative of deep vein thrombosis (Figs 2, 3).
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Figure 2. Axial T1-weighted MR image shows the mass with uniform low signal intensity and with a clear connection to the cecum (black arrow). The cecum (* appears normal. A high-signal-intensity thrombus (white arrow) due to compression of the left external iliac vein by the mass also is visible.
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Figure 3. Axial T2-weighted MR image shows uniform high signal intensity at the center of the mass, with low signal intensity indicative of calcification in the thickened walls of the mass. The connection between the mass and the cecum is clearly visible, as is the compression of the left external iliac vein by the mass. (Fig 3 reprinted, with permission, from reference 1.)
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Pathologic Evaluation
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The imaging features indicated that the patient had a huge appendiceal cystic mass that was causing left-sided deep vein thrombosis. The patient was given anticoagulation therapy (heparin), and, after a detailed discussion between the surgeon and the patient, surgery was undertaken. A limited right hemicolectomy and appendectomy was performed. The resected specimen consisted of the appendix, 9 cm of the cecum, and 4 cm of the terminal ileum (Fig 4). The appendix was grossly enlarged, with a length of 17 cm and a diameter of 6 cm; the lumen was filled with mucoid material (Fig 5). The wall was thickened and firm, with multiple foci of white plaque on the external serosal surface. The mucosa appeared attenuated, but no obvious mucosal lesion was identified. At histologic examination, the cystically dilated distal part of the appendiceal lumen was found to be lined by adenomatous epithelium, which displayed low-grade dysplasia and consisted of a single layer or a pseudostratified layer with papillary projections (Fig 6). The abnormal epithelium was confined to the lumen and did not extend through the appendix wall. There was abundant production of mucin, much of which had calcified, particularly in the proximal part of the appendix. A mucinous cellular infiltrate had penetrated the appendiceal wall, and intermittent foci of mucin were seen on its serosal aspect. Based on these findings, a diagnosis of mucinous cystadenoma of the appendix with mucocele formation was reached.
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Figure 4. Photograph shows the gross pathologic specimen obtained with a limited right hemicolectomy. The cecal wall appears thickened, and white plaque has accumulated on its external surface. (Reprinted, with permission, from reference 1.)
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Figure 5. Transection of the gross specimen shows the appendiceal lumen filled with mucoid material, some of which is calcified, but no focal mass. The mass is clearly localized to the appendix, and the adjoining cecum is normal.
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Figure 6a. (a) Photomicrograph (original magnification, x400; hematoxylin-eosin stain) shows low-grade dysplasia of the neoplastic adenomatous epithelium that lines the distal part of the appendix (arrowhead). (b) Photomicrograph (original magnification, x40; hematoxylin-eosin stain) shows that the neoplastic epithelium consists of a single layer or pseudostratified layer with micropapillary projections (arrow). The abnormal epithelium was confined to the appendiceal lumen and did not extend through the wall.
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Figure 6b. (a) Photomicrograph (original magnification, x400; hematoxylin-eosin stain) shows low-grade dysplasia of the neoplastic adenomatous epithelium that lines the distal part of the appendix (arrowhead). (b) Photomicrograph (original magnification, x40; hematoxylin-eosin stain) shows that the neoplastic epithelium consists of a single layer or pseudostratified layer with micropapillary projections (arrow). The abnormal epithelium was con-fined to the appendiceal lumen and did not extend through the wall.
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Discussion
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Epithelial tumors of the appendix may be classified as mucinous or nonmucinous. Most such tumors are mucin rich, demonstrate circumferential mucosal involvement, and have a strong tendency to form mucoceles (2). Cystadenoma and mucinous cystadenoma are frequently used terms for benign neoplastic mucoceles. The term mucocele is a general macroscopic description that implies a dilated appendiceal lumen caused by an abnormal accumulation of mucus. It does not constitute a pathologic diagnosis; it may be caused by a variety of nonneoplastic, benign neoplastic, and malignant underlying pathologic entities. Mucoceles may be discovered incidentally, at the physical examination or abdominal imaging, or as a secondary surgical finding (3). Most patients present with acute or chronic right lower abdominal pain secondary to cystic distention of the appendix by mucus. A palpable mass is found in up to 50% of patients (4). Patients with an appendiceal mucocele are less likely to present with symptoms of acute appendicitis than are patients with a different tumor of the appendix, because of the chronicity of luminal obstruction seen with mucoceles. Rarer manifestations include intussusception, torsion, gastrointestinal bleeding, altered bowel habits, weight loss, vomiting, and urologic symptoms such as right ureteric obstruction. Approximately 25% of patients with an appendiceal mucocele are asymptomatic (5). Mucoceles of the appendix are rare; they have been observed in only 0.2%–0.3% of surgical appendectomy specimens. They typically occur in people who are middle aged or older, more often in women than in men (6).
Four varieties of mucoceles have been described, according to the predominant feature of the epithelium: One has a normal epithelium, and three show varying degrees of epithelial atypia (3,4,7). The first type, the simple retention cyst, is characterized by a normal appendiceal epithelium and is associated with mild luminal dilatation that rarely exceeds 2 cm in diameter. Any mucocele with a diameter of more than 2 cm is more likely to represent one of the other three types of mucocele (8). The second group, which accounts for 5%–25% of mucoceles, is defined by a hyperplastic epithelium and mild dilatation. In the third group, which accounts for 63%–84% of mucoceles, the appearance of the epithelium is similar to that in villous adenomas and adenomatous polyps of the colon, with mild (low-grade) epithelial dysplasia. Often termed cystadenomas, as in the case presented here, these mucoceles produce marked distention of the lumen; a diameter of 6 cm was demonstrated in our patient. Appendiceal perforation occurs in 20% of cases, with resultant mucinous spillage into the periappendicular area or onto the serosal surface. No neoplastic cells are found in the mucus at histologic examination, and surgical resection is usually curative. The fourth category, which accounts for 11%–20% of cases, encompasses malignant mucinous cystadenocarcinomas. The neoplastic epithelium in these tumors is similar to that seen in adenocarcinomas of the colon, with glandular stromal invasion. Appendiceal distention is severe, and spontaneous rupture has occurred in 6% of cases (4). When the neoplasm is fully developed, implants of neoplastic adenocarcinomatous cells may be found on intraperitoneal surfaces; the extension of the neoplasm is identical to that of intraperitoneal ovarian mucinous cystadenocarcinomas. The term pseudomyxoma peritonei refers to the accumulation of gelatinous material on intraperitoneal surfaces either because of the localized rupture of a benign mucocele or, more commonly, because of the diffuse proliferation of viable neoplastic cells throughout the peritoneum (8). Simultaneous disease is found in the appendix and the ovary in most women with this type of peritoneal extension (9). The peritoneal cavity is distended by adhesive, semisolid mucin. Stocchi et al performed a retrospective analysis of 135 cases of primary appendiceal mucocele to determine whether and how selected clinical, diagnostic, and surgical factors were related to malignancy and surgical management. They found a very strong association between the intraoperative observation of diffuse pseudomyxoma peritonei and malignancy (3).
The pathologic findings in mucinous cystadenomas reflect the classification system. The macroscopic appearance is gross enlargement of the appendix, with luminal distention by mucin. The mucin-rich epithelium often demonstrates a villous architecture. Mucinous cystadenomas tend to be low grade, with circumferential involvement. Progressive mucocele formation results in pressure atrophy and thinning of the wall with fibrosis. The presence of invasive neoplastic cells beyond the muscularis mucosae is indicative of adenocarcinoma (8,10).
Imaging plays an important role in the diagnosis and evaluation of appendiceal neoplasms. CT is the modality of choice because of its ability to depict the anatomic location of a mass, as well as the tissue characteristics. Mural curvilinear calcification aids considerably in the diagnosis but is thought to occur in less than 50% of cases (6,8). The typical finding in cystadenomas of the appendix is a round, thin-walled, encapsulated cystic mass that communicates with the cecum. The attenuation of the contents of the cyst may range from that of water to that of soft tissue, depending on the amount of mucin or debris within the mucocele. Adjacent bowel segments may be displaced, but usually no periappendicular inflammation or abscess is seen (7). These findings help differentiate a mucocele from a periappendiceal abscess or pelvic inflammatory process. Other possible diagnoses, depending on the imaging findings, may be an enteric duplication cyst or mesenteric cyst. Soft-tissue thickening and irregularity of the cystadenoma wall and surrounding fat are nonspecific, atypical findings that suggest malignancy, secondary inflammation, or an unusual pathologic variation. Intraluminal gas bubbles or an air-fluid level within a calcified right lower quadrant cystic mass are helpful indicators of superinfection, which may occur in both benign and malignant variants (8). In suspected cases of the most severe form of this disease entity, pseudomyxoma peritonei, CT is widely used to establish the diagnosis and characterize the extent of disease. MR imaging features of appendiceal cystadenoma recapitulate the CT findings of a cystic mass with low signal intensity on T1-weighted images and high signal intensity on T2-weighted images. MR imaging may be useful for identifying the reproductive organs in female patients to differentiate an appendiceal process from a cystic ovarian lesion or tubo-ovarian abscess. In addition, T2-weighted images may show a peripheral rim with low signal intensity that represents calcification (8).
The treatment of cystic appendiceal masses is primarily surgical excision to eliminate any malignant potential. A laparoscopic approach is not advised, because of the risk of rupture and associated peritoneal extension (11). The type of surgery performed is related to the dimensions and the histologic contents of the mucocele. Appendectomy is performed for cystadenomas and mucosal hyperplasia when the appendiceal base is intact. Because it may be difficult to predict the underlying cause of dilatation merely by inspecting the serosal surface of a dilated appendix, some suggest that a frozen-section examination should be performed while the abdomen is open. Cecal resection is indicated for cystadenomas with a large base, and hemicolectomy is recommended for cystadenocarcinomas (5,7,12). It has been recommended that all mucoceles be removed, particularly those with a diameter greater than 2 cm, because the adenoma-adenocarcinoma progression sequence is believed to be comparable to the colonic adenoma-carcinoma sequence (3). During surgery, full abdominal exploration is advised, as there is an association between appendiceal mucoceles and other tumors, particularly carcinoma of the colon (11%–20%) and tumors of the ovary (2,3,7). In one study, a synchronous tumor for which surgery was considered was found in 29% of patients (3). Patients with a simple or benign neoplastic mucocele have an excellent postoperative prognosis, with 5-year survival rates of 91%–100%, even in cases of extension of mucus into the extra-appendiceal spaces. However, the clinical course of diffuse pseudomyxoma peritonei is insidious and unrelenting. Treatment consists of aggressive surgical debulking of all apparent mucinous tissue and, in women, bilateral oophorectomy or total abdominal hysterectomy. This approach, compared with appendectomy alone, leads to a significant improvement in the survival rate and decreased recurrence.
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Footnotes
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Editor’s Note.—Everyone who has taken the course in radiologic pathology at the Armed Forces Institute of Pathology (AFIP) remembers bringing beautifully illustrated cases for accession to the Institute. In recent years, the staff of the Department of Radiologic Pathology has judged the "best cases" by organ system, and recognition is given to the winners on the last day of the class. With each issue of RadioGraphics, one or more of these cases are published, written by the winning resident. Radiologic-pathologic correlation is emphasized, and the causes of the imaging signs of various diseases are illustrated.
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References
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- Persaud T, Buckley O, Geoghegan T, McCourt M, Swan N, Torreggiani WC. Giant mucinous cystadenoma of the appendix presenting with contralateral ileo-femoral deep vein thrombosis. Eur Radiol 2005;10:2212–2213.
- Carr NJ, McCarthy WF, Sobin LH. Epithelial noncarcinoid tumors and tumor-like lesions of the appendix: a clinicopathologic study of 184 patients with a multivariate analysis of prognostic factors. Cancer 1995;75:757–768.[CrossRef][Medline]
- Stocchi L, Wolff B, Larson D, Harrington J. Surgical treatment of appendiceal mucocele. Arch Surg 2003;138:585–589.[Abstract/Free Full Text]
- Rampone B, Roviello F, Marrelli D, Pinto E. Giant appendiceal mucocele: report of a case and brief review. World J Gastroenterol 2005;11(30): 4761–4763.[Medline]
- Macek D, Jafri SZ, Madrazo BL. Ultrasound case of the day: mucocele of the appendix. RadioGraphics 1992;12(6):1247–1249.[Medline]
- Madwed D, Mindelzun R, Jeffrey RB Jr. Mucocele of the appendix: imaging findings. AJR Am J Roentgenol 1992;159:69–72.[Abstract/Free Full Text]
- Deans GT, Spence RA. Neoplastic lesions of the appendix. Br J Surg 1995;82:299–306.[Medline]
- Pickhardt PJ, Levy AD, Rohrmann CA, Kende AI. Primary neoplasms of the appendix: radiologic spectrum of disease with pathologic correlation. RadioGraphics 2003;23:645–662.[Abstract/Free Full Text]
- Hinson FL, Ambrose NS. Pseudomyxoma peritonei. Br J Surg 1998;85:1332–1339.[CrossRef][Medline]
- Gibbs NM. Mucinous cystadenoma and cystadenocarcinoma of the vermiform appendix with particular reference to mucocele and pseudomyxoma peritonei. J Clin Pathol 1973;26:413–421.[Abstract/Free Full Text]
- Gonzalez Moreno S, Shmookler BM, Sugarbaker PH. Appendiceal mucocele: contraindication to laparoscopic appendectomy. Surg Endosc 1998; 12:1177–1179.[CrossRef][Medline]
- Lakatos PL, Gyori G, Halasz J, et al. Mucocele of the appendix: an unusual cause of lower abdominal pain in a patient with ulcerative colitis—a case report and review of literature. World J Gastroenterol 2005;11(3):457–459.[Medline]
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History
Imaging Findings
