OBJECTIVETo study the clinicopathologic characteristics of perivascular epithelioid cell tumor (PEComa), not otherwise specified (NOS) and to evaluate the diagnostic criteria for malignancy.

METHODSThe clinical and pathologic features of 31 cases of PEComa-NOS were reviewed. The follow-up data available were analyzed.

RESULTSThere were a total of 24 females and 7 males. The age of the patients ranged from 13 to 66 years (mean = 40 years). The site of tumor occurrence included gynecologic organs (n = 12), intraabdominal/peritoneal soft tissue (n = 10), gastrointestinal tract (n = 4), thigh (n = 2), mediastinum (n = 1), left groin (n = 1) and urinary bladder (n = 1). None of the cases was associated with tuberous sclerosis complex. Histologic examination showed that 23 cases (74%) were clear cell sugar tumor-like, 4 cases (13%) were clear cell myomelanocytic tumor-like and 4 cases (13%) were of mixed epithelioid-spindled morphology. According to the classification system proposed by Folpe et al, 19 cases (61%) were classified as malignant, 7 cases (23%) as PEComa of uncertain malignant potential and 5 cases (16%) as benign. The expression rates of HMB45, smooth muscle actin and desmin in tested cases were 100% (31/31), 67% (14/21) and 6/18, respectively. Follow-up data (1 to 56 months) were available in 23 cases (74%). Amongst the 16 cases of malignant PEComa, 7 patients were still alive with no evidence of disease, 6 patients were alive with unresectable or recurrent/metastatic disease and 3 patients died of the disease. The local recurrence and metastasis in those 16 cases were 6 cases and 5 cases, respectively. One of the 4 patients with PEComa of uncertain malignant potential died, while the remaining 3 patients and all of the patients with benign PEComa had an uneventful clinical course.

CONCLUSIONSThe classification system of PEComas proposed by Folpe et al. is reliable in routine practice. Correlation with the clinical and radiologic findings however is prudent when dealing with core biopsy specimens or sampling from exploration laparotomy. Owing to the histologic heterogeneity of this entity, thorough understanding of the morphologic spectrum is essential in arriving at a correct diagnosis.