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BACKGROUND: Desmoplastic small round cell tumor (DSRCT) is a rare lethal malignant tumor with young male predominance. The majority of cases arise in the abdominopelvic region and are hypothesized to have a mesothelial origin. However, extra-abdominal and extraperitoneal DSRCT have been reported. It is extremely uncommon for the pancreas to be a primary site for DSRCT, and only 5 cases have previously been reported in the English literature. Clinically, DSRCT has a wide range of presentations from asymptomatic to life-threatening comorbidity, and it responds poorly to treatment despite aggressive therapy.
CASE REPORT: We report a previously healthy 9-year-old boy with an incidentally discovered abdominal mass of pancreatic origin. All necessary laboratory investigations were within normal limits. Computed tomographic imaging showed a huge left-side retroperitoneal mass measuring 15 cm in the greatest dimension that was accompanied by vascular encasement. The mass was resected successfully. Histopathological examination along with ancillary tests favored a diagnosis of DSRCT over other small round blue cell tumors. Detection of translocation t(11;22)(p13;q12) with EWSR1-WT1 gene fusion, based on reverse transcription-polymerase chain reaction analysis, confirmed the diagnosis. Approximately 7 months later, the tumor recurred with mesenteric lymph nodes metastasis and the child was placed on palliative therapy.
CONCLUSIONS: It is worthwhile to consider DSRCT in the differential diagnosis of small round blue cell tumors, even in unusual sites, in a pediatric age group. Due to the poor prognosis, owing to chemotherapy resistance and a high rate of recurrence with significant tumor burden, reaching a precise diagnosis of DSRCT is essential. Almost all cases harbor the hallmark molecular alteration of t(11;22)(p13;q12) with EWSR1-WT1 gene fusion. Debulking surgery paired with a chemotherapy regimen comprising vincristine, doxorubicin, and cyclophosphamide and ifosfamide + etoposide has been shown to improve overall survival rate compared with other chemotherapeutic agents. However, no targeted therapeutic modality has been developed.

Keywords: desmoplastic small round cell tumor, Pancrelipase, Pediatrics