A Rare, yet Aggressive, Intra-Abdominal Malignancy: Ewing Sarcoma of the Pancreas

Abstract

Introduction: Ewing sarcoma (ES) is a malignant bone tumor of long-bones, which typically occurs in children. Extraskeletal Ewing sarcoma (EES) is a poorly differentiated soft tissue sarcoma within morphologic category of ‘small-round-cell’ tumors and accounts for less than 1% of soft tissue sarcomas. Only 24 cases have been reported in the literature. Herein, we present an interesting case of EES of pancreas. Case Description: 34-year-old male presented to clinic secondary to insidious onset, generalized abdominal pain for past 1-month. Physical exam revealed non-tender, moderately distended abdomen with a palpable mass above the umbilicus. Initial lab workup showed mild elevation of AST 91 (0-50 U/L) and alkaline-phosphatase 337 (38-126 U/L). CT abdomen showed lobulated heterogeneous mass with necrotic transformation in body and tail of pancreas, with multiple liver lesions. Resultantly, a working diagnosis of adenocarcinoma of pancreas with metastasis to liver was made. A CT-guided biopsy of pancreatic and hepatic mass showed small, blue, round cells with scant cytoplasm. Hence, the previous diagnosis of pancreatic adenocarcinoma was disregarded, and other differential diagnoses including EES, neuroblastoma, non-Hodgkin's lymphoma vs desmoplastic small blue round cell tumor were considered. Further testing with immunohistochemistry confirmed the diagnosis of EES. Subsequently, patient was started on chemotherapy with doxorubicin, cyclophosphamide and vincristine. After one round of chemotherapy, patient developed neutropenic fever and died after 1-month from a complicated hospital course. Discussion: This case highlights an extremely rare type of soft tissue sarcoma (EES) at an unusual location. The diagnosis of ESS is confirmed by immunohistochemistry as imaging modalities often remain nonspecific. Histologically, ES and EES are described as small, blue, round cells with hyperchromatic nuclei and scant cytoplasm, with molecular expression of MIC2, CD99 and antibody against FLI1 centered in nucleus. Though 85% of the ES cases are associated with chromosomal translocation t(11;22) and q(24;12), it remains non-specific. EES is an aggressive and malignant tumor with a 5-year survival rate of around 50%. Surgical excision, plus chemotherapy and radiotherapy is the main modality of treatment. Though EES is rare, physicians should be acquainted with and consider it in the differential diagnosis, as early recognition and intervention is very critical.1397_A.tif Figure 1: Necrotic mass (14.8cm x 5.6cm x 6.7cm) again visualized in the pancreas along with multiple hypo-attenuated liver lesions.1397_B.tif Figure 2: Small, blue, round cells with high NC ratio, dark chromatin pattern with scant cytoplasm. Tumor cells positive for vimentin; negative for CD45, CD117, chromogranin, synaptophysin, pan cytokeratin, smooth muscle actin, desmin, HMB-45, S-100 and CD138. Pattern is highly consistent with high grade soft tissue sarcoma- EES.