A 16-year-old girl presented with an asymptomatic abdominal lump which became apparent since the preceding one month. A computed tomography (CT) scan revealed a large lobulated heterogeneous mass extending from the splenic hilum to the dome of the urinary bladder measuring about 21 × 15 × 10 cm in its maximum cranio-caudal, transverse and antero-posterior extents . The mass displaced the stomach, small bowel and abutted the pancreatic body and tail. No definite organ of origin could be determined due to the large size. However, it appeared to be arising from the retroperitoneum. The tumor volume was estimated to be 4205.8 cubic cm. A core biopsy revealed a malignant round cell tumor. The tumor cells expressed vimentin and Mic-2. The clinicopathological features favored a primitive neuroectodermal tumor (PNET). The metastatic work-up including bone marrow studies, bone scan, and CT scan of thorax was negative.
(a, b): Coronal and sagittal CT scan images showing a large lobulated mass occupying the gastro-splenic and gastro-pancreatic regions and extending inferiorly. Tortuous portal vein, SMV and splenic vein are noted
Combination chemotherapy was initiated as per the institutional protocol for PNET comprising of a six drug regimen of vincristine, doxorubicin, cyclophosphamide, actinomycin D, ifosfamide and etoposide. After the initial nine weeks of induction therapy, CT scan showed a persistent mass with no change in the extent of the disease.
On exploratory laparotomy, the mass was densely adherent to the greater curvature of the stomach and the transverse colon was draped over the anterior surface. After extensive and meticulous dissection, the mass was found to be arising from the body and tail of pancreas. Distal pancreatectomy with splenectomy and transverse colon resection was performed and the bowel continuity restored with an end-to-end colocolic anastomosis. Thorough search of the peritoneal cavity revealed a few peritoneal nodules on the posterior wall of the pylorus, porta, and peripancreatic region which were also resected.
Grossly, the mass measured 24 × 17 × 9 cm and the cut surface largely consisted of areas of necrosis with lobulated fleshy, white areas . Microscopically, the tumor was composed of small round malignant cells with focal fibrous septa and necrosis. The tumor cells were also seen invading the intestine and the splenic hilum . The portal and peripancreatic nodules also showed viable tumors. On immunohistochemistry, the tumor cells expressed desmin. Immunostaining with CD99 was equivocal and the cells showed cytoplasmic, but not nuclear, expression of WT1. The histologic and immunohistochemical features were overlapping with those of PNET and DSRCT. Hence molecular studies were performed. Reverse transcriptase polymerase chain reaction (RTPCR) using RNA extracted from formalin fixed paraffin embedded revealed EWS-WT1 gene fusion chimeric transcript, confirming a diagnosis of DSRCT. RT-PCR for EWS-FLI1 translocation was negative.
Gross specimen showing the mass along with spleen and transverse colon draped over it. Pancreatic stump is also seen (held with forceps)
a) A malignant small round cell tumor infiltrating the b) pancreas and c) the wall of the colon. d) Strong cytoplasmic positivity for antibody to desmin on immunohistochemistry. e) EWS-WT1 fusion transcript as demonstrated by RT-PCR
The patient received abdominopelvic radiotherapy along with concurrent chemotherapy following which maintenance chemotherapy was initiated. The patient developed intractable upper gastrointestinal bleeding manifested by hematemesis and melena, which significantly curtailed maintenance chemotherapy. The exact cause of the bleeding could not be ascertained but was attributed to the abdominopelvic radiotherapy. The patient, however, responded to prolonged conservative management and is now on regular follow-up with serial ultrasound examination. At 14 months from the last chemotherapy, the patient remained disease-free.