PEComas of the colon and rectum: a case report of a 15-year-old girl and a review of the pertinent literature.

Perivascular epithelioid cell tumors (PEComas) are rare mesenchymal neoplasms characterized by perivascular epithelioid cells. PEComas include angiomyolipoma (AML) of the kidney, clear-cell sugar tumor (CCST), lymphangioleiomyomatosis (LAM) and clear-cell tumors of other anatomical locations. PEComas other than AML, CCST and LAM are very rare tumors that have been referred to as PEComa-not otherwise specified (PEComa-NOS). Especially, colorectal PEComa-NOS remains very rare. A 15-year-old girl underwent a colonoscopy due to hematochezia, thus revealing a 30 mm intramural mass in the upper rectum. The patient was treated by laparoscopic high anterior resection under the diagnosis of Gastrointestinal stromal tumor. Histologically the tumor was positive for HMB45 (human melanoma black 45), TFE3 (transcription factor binding to IGHM enhancer 3), which suggested the diagnosis of PEComa-NOS. The patient remains recurrence-free at five years postoperatively. The treatment strategy, prognosis, and biological behavior of PEComa-NOS is still unclear. We also review the pertinent literature on colorectal PEComa-NOS.