(Radiographics. 1999;19:1693-1695.)
© RSNA, 1999
Pediatric Case of the Day1
Maria S. Figarola, MD and
Salah M. Khader, MD
1 From the Department of Radiology, University of South Alabama College of Medicine, 2451 Fillingim St, 301 Mastin Bldg, Mobile, AL 36617. Received May 3, 1999; revision requested May 19 and received June 15; accepted June 21. Address reprint requests to M.S.F.
Index Terms: Neoplasms, in infants and children, 80.32 • Pelvis, CT, 80.12112 • Pelvis, neoplasms, 80.32
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HISTORY
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A previously healthy 8-year-old boy presented to the emergency department with complaints of constipation, dysuria, and difficulty in micturition that had been progressive over the past 6 weeks. Several enema procedures and symptomatic treatment had failed to resolve his symptoms prior to presentation. At physical examination, a firm, palpable abdominal mass was discovered extending from the symphysis pubis to about 3 cm above the umbilicus. Abdominal radiography and computed tomography (CT) of the abdomen and pelvis were performed. Further work-up included laboratory tests, bone scintigraphy, and chest CT.
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FINDINGS
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Abdominal radiography showed evidence of distal large bowel obstruction with dilation of both the small and large bowel. A large mass could be seen arising from the pelvis and displacing the dilated bowel superiorly (Fig 1).
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Figure 1. Supine radiograph of the abdomen shows dilation of both small and large bowel loops with no air in the distal colon and rectum. A large soft-tissue mass is seen arising from the pelvis and extending into the abdomen, displacing the bowel loops.
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CT of the abdomen showed a well-defined, inhomogeneous soft-tissue mass arising within and occupying the entire pelvis and extending into the abdomen (Fig 2). No calcification or hemorrhage was noted. There was no bone invasion or remodeling, and the urinary bladder was displaced anterosuperiorly. The rectum was severely compressed and invaded by the mass. A sliver of air was seen along the right lateral aspect of the mass and probably represented residual air in the involved bowel. The mass was associated with bilateral mild hydronephrosis that was worse on the left side (Fig 3). Laboratory results and findings at bone scintigraphy and chest CT showed no evidence of distant metastasis.
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Figure 2. Contrast material-enhanced CT scan of the upper pelvis shows a large, well-defined, inhomogeneous mass filling the pelvis. The urinary bladder contains a Foley catheter and is compressed anteriorly. A sliver of air is noted along the right lateral aspect of the mass and probably represents residual air in the involved bowel. Note the absence of bone invasion.
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Figure 3. Contrast-enhanced abdominal CT scan obtained at the level of the kidneys shows bilateral mild hydronephrosis that is worse on the left side, with slight delay of contrast material excretion into the left collecting system.
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DIAGNOSIS: Extrarenal rhabdoid tumor of the pelvis.
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DISCUSSION
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The discovery of a solid, presacral mass in a pediatric patient initially raises suspicion for a sacrococcygeal teratoma, a rhabdomyosarcoma of prostatic or other origin, or some other soft-tissue sarcoma. Pelvic rhabdoid tumors are extremely rare; only a few reports of this entity are found in the literature.
Rhabdoid tumor was first described in the kidneys and was initially thought to be a sarcomatous variant of Wilms tumor (1). The exact cell of origin is still not known. Renal rhabdoid tumor has been described as a solid tumor that is seen only in childhood, with most cases occurring in the 1st year of life (2,3). These tumors are usually large at presentation and demonstrate necrosis and calcification more commonly than Wilms tumor. Affected patients have a dismal 18-month survival rate of only 20% (4). Interesting features of renal rhabdoid tumors include their association with hypercalcemia, the presence of lobulation at radiology, and occasional subcapsular hematoma formation (1,4).
The existence of extrarenal rhabdoid tumors has been controversial, partly because of the broad spectrum of primary sites including the extremities, brain, and heart; however, increasing evidence for the existence of this tumor in growing numbers of case reports has led to its being widely accepted as a discrete entity. The two largest series of extrarenal soft-tissue tumors with a rhabdoid phenotype were reported by Parham et al (5) and Kodet et al (6).
Extrarenal rhabdoid tumors are nonmyogenous (ie, they do not demonstrate skeletal muscle components at immunohistochemical analysis or electron microscopy); consequently, the term rhabdoid is used to differentiate them from rhabdomyosarcomas. The tumors generally have a histologic appearance similar to that of renal rhabdoid tumors.
Extrarenal rhabdoid tumors have been described in the liver, brain, tongue, neck, chest, heart, pelvis, extremities, and several other sites (6). These tumors typically occur in infancy; median patient age in one large series was 20 months. However, patient age ranges from 3 weeks to 50 years (5). The tumors have a 1.5:1 male predilection (5), and death occurs an average of 6 months after diagnosis. Data concerning the 5-year survival rate are not available.
The rhabdoid phenotype consists of histologic, cytopathologic, and cytogenetic findings. This embryonal neoplasm demonstrates large cells with large nuclei and nucleoli. There is abundant cytoplasm containing eosinophilic inclusions that harbor intermediate filaments at electron microscopy. The cells demonstrate solid growth without rosette formation or further differentiation. Immunohistochemical analysis usually demonstrates reactivity to vimentin, desmin, and keratin (1,6). Cytogenetic analysis classically demonstrates a balanced translocation involving the short arm of chromosome 6 (6p12) and the long arm of chromosome 22 (22q11) (7).
The imaging characteristics of soft-tissue rhabdoid tumors have yet to be determined, largely owing to the rarity and the relatively recent recognition of these tumors (8).
In our patient, surgical biopsy of the mass was performed, followed by bilateral nephrostomies, internal ureteral stent placement, and initiation of chemotherapy. At first, the patient demonstrated clinical and radiologic improvement (Fig 4); however, this was followed by a protracted course of progressive tumor enlargement, intestinal obstructive symptoms, and respiratory compromise due to abdominal distention. A palliative diverting colostomy was performed. The patient's condition continued to worsen despite aggressive chemotherapy, and he died almost 4 months after diagnosis.
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Figure 4. Supine radiograph of the abdomen obtained after the first course of chemotherapy shows placement of bilateral ureteral stents and resolution of the obstructive pattern of bowel loops.
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References
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Sisler C, Siegel M. Malignant rhabdoid tumor of the kidney: radiologic features. Radiology 1989; 172:211-212.[Abstract/Free Full Text]
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Parham D. Pediatric neoplasia: morphology and biology Philadelphia, Pa: Lippincott-Raven, 1996; 54-55.
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Isaacs H, Jr. Tumors. In: Gilbert-Barness E, eds. Potter's pathology of the fetus and infant. 1st ed. St Louis, Mo: Mosby–Year Book, 1997; 1242-1339.
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Chung C, Lorenzo R, Rayder S, et al. Rhabdoid tumors of the kidney in children. AJR 1995; 164:697-700.[Abstract/Free Full Text]
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Parham D, Weeks D, Beckwith JB. The clinicopathologic spectrum of putative extrarenal rhabdoid tumors. Am J Surg Pathol 1994; 18:1010-1029.[Medline]
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Kodet R, Newton W, Sachs N, et al. Rhabdoid tumors of soft tissues. Hum Pathol 1991; 22:674-684.[Medline]
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Perlman E, Ali S, Robinson R, et al. Infantile extrarenal rhabdoid tumor. Pediatr Dev Pathol 1998; 1:149-152.[Medline]
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Howlett DC, King AP, Jarosz JM, et al. Imaging and pathological features of primary malignant rhabdoid tumours of the brain and spine. Neuroradiology 1997; 39:719-723.[Medline]
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HISTORY
FINDINGS
