Malignant perivascular epithelioid cell tumor of the colorectum: Clinicopathological characterization, diagnosis and treatment process of 7 cases

BACKGROUND Perivascular epithelioid cell tumor (PEComa) of the colorectum is exceedingly rare, with only a few published reports. It presents with a wide spectrum of biological behavior, ranging from benign to malignant. The prognosis for malignant PEComa is poor and there is little consensus on its treatment. AIM To fully characterize PEComa and standardize its diagnosis and treatment. METHODS Patients with colorectal malignant PEComa were identified from the First Affiliated Hospital, Zhejiang University School of Medicine and People's Hospital of Anji. Cases with controversial pathology and cases lost to follow-up were excluded, leaving seven remaining cases that formed the basis of the study. We collected relevant clinicopathological, therapeutic and followup details. Disease stage and progression were assessed by contrast-enhanced computed tomography at baseline and at 3-month intervals. RESULTS The mean age was 43 years, with a range of 5 years to 73 years. The average body mass index was 21.8 +/- 3.0 kg/m2, and 71.4% of cases occurred in the colon. The main symptoms of colorectal PEComas were abdominal mass and hematochezia. The most common microscopic finding of malignant behavior was infiltrative growth. Immunohistochemical analysis found that 6/7 cases were positive for HMB45, 5/7 were positive for melan-A, and 3/5 were positive for MiTF. The watch-and-wait approach to treatment was a risky option. Radical resection was preferable to systemic treatment. The median progression-free survival exceeded 38 months, longer than previously reported. CONCLUSION Radical or extended resection is the key to prolonged survival of malignant PEComa. More meaningful studies are urgently needed to establish the standardized diagnosis and treatment.