PECOMA - A Histological Surprise

A B S T R A C T INTRODUCTION Perivascular epithelioid cell tumor (PEComa) is rare neoplasm arising from mesenchymal cells with distinctive histologic, immunohistochemistry and clinical characteristics. It probably arises through activation of the mTOR signaling pathway. Malignant PEComa are extremely rare with very few cases being reported in literature. They occur at various anatomic sites in the body and have distinctive clinical presentation and variable prognosis. PRESENTATION OF CASE We present a case of 39 yr old male patient who presented with anemia and palpable abdominal mass. He had previous history of two laprotomies for abdominal mass histologically suspected of GIST. He was evaluated with regular blood investigations, bone marrow examination and CECT Abdomen. Laprotomy was done and a tumor was found arising from the previous anastomotic site and transverse mesocolon. Clinically suspected as recurrent/malignant GIST, tumor was excised and sent for histopathology examination. At histopathology tumor sections showed perivascular pattern of spindle shaped epithelioid cells with atypia, high mitotic figures, and necrosis. IHC marking was positive for HMB45, SMA, Melan-A, Desmin, and immunonegative for S-100, ckit and DOG-1. Thus confirming the diagnosis of Malignant PEComa and patient kept on follow up. DISCUSSION The earliest description of PEComa date back to 1943 when they were first described as an abnormal myoblast found in section specimen of renal angiomyolipoma. PEComa are rare tumors with variable presentation. There have been around 100 reported cases of PEComa with around 55 being malignant. Malignant PEComas of GIT are even rarer with few cases reported. They have an aggressive course with mean life time of around 30months. CONCLUSION Malignant PEComas are very rare tumors with aggressive course and no known effective treatment. The information we have are from various case series and reports. The article is to sensitize the occurence of this tumor in case of histologically proven GIST, its clinical and histologic diagnostic difficulties and probable treatment options. PEComa, HMB45, SMA, DESMIN, Malignant PEComa, Colon, Recurrent GIST