Pancreatic Fibromyxoid Sarcoma: A Rare Variant

Abstract

Introduction: A 53-year-old man presented to our emergency department with 3 months of dull left flank pain. Initial evaluation demonstrated normal physical exam and lab values; he was discharged with pain medication. The pain persisted and he returned to the ED. A CT scan showed a calcified mass in the body of his pancreas. Labs at this time showed normal liver tests but his lipase was mildly elevated at 65 units/L. Endoscopic ultrasound (EUS) was performed and demonstrated a 3.7 x 3.2 cm calcified, hypoechoic mass with associated upstream dilation of the pancreatic duct to 9 mm. FNA was nondiagnostic. At this point, the differential included carcinoma, neuroendocrine neoplasm, gastrointestinal stromal tumor, epithelioid angiomyolipoma, solid pseudopapillary neoplasm, fibromatosis of the pancreas, or focal chronic pancreatitis. Surgical consultation was requested and distal pancreatectomy was recommended. A 7-cm tumor was found in the pancreatic body and tail. Frozen sections showed carcinoma most consistent with a neuroendocrine tumor. Histology showed vascular invasion into the splenic vessels without evidence of lymph system invasion. H&E sections revealed a mild to moderately cellular lesion composed of spindled and epithelioid cells in a hyalinized matrix. There was focal mature bone within tumor, but no malignant epithelial component. The tumor invaded pancreatic parenchyma extensively. Immunostains for CD34 and GLUT-1 showed patchy positivity within tumor. The tumor was negative for cytokeratin 7, cytokeratin AE1/AE3, epithelial membrane antigen, desmin, actin, and S-100 immunostains. A MUC-4 immunostain was strongly positive. The combinations of the histological and immunohistochemical findings are consistent with a low-grade fibromyxoid sarcoma (LGFMS) with sclerosing epithelioid fibrosarcoma (SEF) variant. SEF is a variant of LGFMS. These tumors are often found in the extremities and less often in the groin, trunk, and neck. Abdominal LGFMS/SEFs are almost exclusively been reported in the retroperitoneum. These rare tumors were first identified as a unique sarcoma in 1995 and approximately 100 individual cases have been identified. Only 1 case of LGFMS/SEF of the pancreas exists in the literature. We provide another case. Based on a small patient case series of LGFMS/SEF, local recurrence is seen in as many as 37-48% of cases with a distant metastasis rate of 36=60% and mortality rates are around 35%. Our case has invasion of the splenic vein, but to date there is no evidence of metastatic disease after undergoing primary resection with external beam radiation. He continues to undergo quarterly surveillance imaging.