Definition
To date, all patients have been women, predominantly in the fifth or sixth decade of life.
The tumour most often occurs in the retroperitoneum, occasionally in the anterior abdominal wall, uterus or pelvis.
The tumour is usually circumscribed. It may be solid or cystic. The consistency varies from firm and rubbery to friable. There may be calcification.
The tumour cells are bland and epithelioid with pale granular to clear cytoplasm. The cells form trabeculae surrounded by abundant densely sclerotic stroma. There may be spindle cell or sheet like areas of tumour cells. At least focally, the tumour cells associate with the walls of blood vessels and resemble an angiomyolipoma but fat is lacking. The nested appearance of other types of PEComa is usually not seen. Rarely there are rhabdoid cytoplasmic inclusion or prominent nuclear pseudo-inclusions. The mitotic rate is usually low but some tumours show areas of marked pleomorphism associated with a high mitotic rate.
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3/131 |
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11/12 1 |
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1/121 |
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0/131 |
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0/131 |
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0/131 |
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Epithelioid smooth muscle tumours have brightly eosinophilic cytoplasm and are negative for HMB45 and MiTF.
Metastatic carcinoma, unlike PEComas, is cytologically malignant and is positive for cytokeratin and EMA.
©SMUHT/PW Bishop