PEComa

Perivascular epithelioid cells (PEC) have no known normal cellular counterpart. However, there are a number of tumours showing PEC differentiation. The term PEComa is sometimes used generically for this family of tumours, sometimes more specifically for extra-pulmonary, extra-renal epithelioid tumours showing evidence of both melanocytic and muscle differentiation but lacking an adipocytic component.

The family of PEComas include:

• pulmonary clear cell (sugar) tumours

• extrapulmonary clear cell tumours. These occur at diverse sites, including breast, trachea, heart, pancreas, rectum, uterus and perineum.

• clear cell myomelanocytic tumour of the falciform ligament / ligamentum teres / common bile duct

• angiomyolipomas: these may be renal or extrarenal, including the nasal cavity

• lymphangiomyomas

• lymphangioleiomyomatosis

• renal capsuloma

• renal microhamartoma

Malignant PEComas (abdominopelvic sarcoma of perivascular epithelioid cells) have been reported in the skull base, abdominal wall, jejunum, ileal serosa, prostate, uterus and pelvis. There is hypercellularity, pleomorphism, prominent coagulative necrosis and lymphovascular invasion. Mitotic rates are variable but are greater than 1 per 50 HPF. Metastases occur to lymph nodes, ovaries, liver, lung and bone.

References

¹ Hornick JL,Fletcher CD. PEComa: what do we know so far? Histopathology 2006; 48:75-82

² Folpe AL, Mentzel T, Lehr HA, et al. Perivascular epithelioid cell neoplasms of soft tissue and gynecologic origin: a clinicopathologic study of 26 cases and review of the literature. Am J Surg Pathol 2005; 29:1558-75

This page last revised 19.4.2006.

©SMUHT/PW Bishop