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Findings: An air contrast barium enema demonstrated persistent, asymmetric narrowing of the splenic flexure. The folds appeared spiculated, particularly oat the medial aspect. The remainder of the colon appeared normal. An extrinsic, inflammatory process was suspected as the cause of the asymmetric narrowing and a CT scan was performed.

The CT showed abnormal soft tissue in the region of the body and tail of the pancreas which encircled the contrast filled splenic flexure. The splenic vein was thrombosed.

There was peritoneal carcinomatosis, ascites and multiple omental and mesenteric nodules. There was metastatic extension along the falciform ligament, and into the porta hepatis.

There was spread into the retroperitoneum with metastases to the adrenal glands and multiple small retroperitoneal lymph nodes.

There were bilateral pleural effusions and multiple cardiophrenic lymph nodes.

The patient was treated with chemotherapy but returned six months later with bone pain. Multiple blastic lesions were seen throughout the spine and pelvis as well as in unusual locations such as the distal tibia. The bone scan showed diffuse metastases with poor visualization of the kidneys. The metaphyses of all the long bone showed evidence of metastases and there were a few solitary lesions in the skull.

Diagnosis:Desmoplastic small round-cell tumor (DSRCT) of the abdomen in childhood with widespread metastatic disease.

Additional Case Information: Six months later, a second child was diagnosed at Rainbow Babies and Children's Hospital with the same diagnosis.

Clinical history: A six year old boy was initially asymptomatic except for a right inguinal hernia. At surgery a mass was discovered in the right hemiscrotum. The mass was biopsied and a CT was obtained for staging.

Findings: There was a 6cm heterogeneous mass superior and lateral to the right kidney. The mass displaced the left kidney inferiorly and displaced or invaded the posterior segment of the right lobe of the liver. Laterally, the tumor invaded the ribs and intercostal muscles of the lateral body wall. The mass also invaded the diaphragm and there was an associated right pleural effusion.

Images through the pelvis showed a large amount of ascites and diffuse peritoneal and omental studding. There was extension into the scrotum along the spermaticord, presumably through a patent processus vaginalis. The family elected to have supportive care only. Although the patient was asymptomatic at the time of presentation for hernia repair, he was dead within six weeks.

Discussion: DSRCT of the abdomen is a rare, highly malignant tumor which primarily affects young adolescent males. The primary tumor, when one is identified, is typically localized to the abdomen and is associated with diffuse peritoneal serosal involvement. Occasionally, there may be diffuse disease without any dominant mass representing the primary tumor.

The histology of this tumor is a small, blue round cell. The cell of DSRCT is a multipotential cell which can exhibit epithelial, mesenchymal and neural features. Special immunohistochemical studies as well as cytogenetic studies are necessary to distinguish this tumor form other small round cell tumors such as Ewings sarcoma. The immunuohistochemistry stains are positive for cytokeratin, desmin and neuron-specific enolase. The cytogenetics show an abnormal karyotype with a specific translocation t(11;22) (p13;q12) associated this tumor. It is different from the translocation of Ewings sarcoma, t(11,22) (q24,q12), but involves the same break point on chromosome 22(q12).

The tumor has a very aggressive clinical behavior. Therapy may include debulking surgery and chemotherapy but the prognosis is very poor.

References:
Gerald, WL, Miller, HK., Battifora, H, Miettinen, M,
Silva, EG, Rosai, J. Intra-abdominal Desmoplastic
Small Round-Cell Tumor: Report of 19 Cases of a
Distinctive Type of High Grade PolyphenotypicMalignancy
Affecting Young Individuals. Am J Sirg Path1991;15(6): 499-513.

Ladanyi,M, Gerald,W. Fusion of the EWS and WT1 Genes
in the Desmoplastic Small Round Cell Tumor. Cancer
Research 54:2837-2840, 1994.

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