Colic PEComa: one disease, two outcomes.

Dear Editor: Perivascular epithelioid cell (PEComa) tumour, also known as PEC tumour, is defined by the World Health Organization (WHO) as a mesenchymal tumour composed of perivascular epithelioid cells. It is an extremely rare tumour, which can affect any part of the body. PEComa expresses both melanocytic and smooth muscle markers. It is part of a family of tumours which includes lymphangioleiomyomatosis (LAM) which generally affects premenopausal women causing nodular and in te rs t i t i a l pu lmonary les ions ; angiomyolipoma (AML) which includes often asymptomatic liver and kidney lesions consisting of muscular, vascular and adipose tissue; and pulmonary and extra-pulmonary clear-cell Bsugar^ tumours (CCSTs). PEComa can exhibit an array of behaviours ranging from benign tumours to aggressive sarcomas. It has been shown that aggressive clinical course is associated with increased atypia, mitotic activity, necrosis, and infiltrative margins, but there is still no reliable predictor of malignancy. In addition, PEComa of the colorectal area involves specific management, including complex, multi-stage surgery in some patients. We report two colic PEComas with different outcomes and review the published literature on colorectal PEComa. Case 1 A 20-year-old male patient with no past medical history consulted the emergency department after the sudden onset of acute abdominal pain in the right upper quadrant. He had presented one episode of vomiting, had no fever, and was hemodynamically stable. The abdominal palpation showed rigidity of the right hemiabdomen without rebound tenderness. Blood laboratory tests, including white blood count, liver function tests, creatinine, and C-reactive protein, were within normal range. Abdominal ultrasound showed free intraperitoneal fluid and a heterogeneous nodular structure lying between the right kidney and the lower part of the liver. A computed tomography confirmed the presence of the lesion, measuring 49×46×40 mm, which was supplied by a branch of the superior mesenteric artery. The lesion was compatible with a gastrointestinal stromal tumour (GIST), and the free intraperitoneal fluid of heterogenous density suggested the presence of blood. An arteriogram excluded an active bleeding. The lesion was further characterized by magnetic resonance imaging, which revealed that the tumour was composed of fluid and solid tissue and that it was most likely originating from the anti-mesenteric side of the ascending colon. The patient underwent an exploratory laparotomy, and coagulated blood was found in the abdominal cavity. A radical right hemicolectomy with latero-lateral anastomosis was carried out. There were no postoperative event, and the patient was discharged after 4 days. The surgical specimen showed a 8-cm mass located in the pericolic adipose tissue. Histology showed a lesion with cytoarchitectural features of a sclerosing PEComa. The lesion consisted of fascicles of spindle-shaped cells with granular eosinophilic cytoplasm and plump vesicular nuclei. There was no significant atypia or pleomorphism. In many areas, the tumour cells were associated with coarse collagen bundles or nodules. Immunohistochemistry showed diffuse desmin * Al-Naimi Noof dr-alnaiminoof@hotmail.com