Perivascular epithelioid cell tumors (PEComas)

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Perivascular epithelioid cells tumors (PEComas) are a group of related mesenchymal tumors and tumor-like conditions found in many locations. This group includes:

• angiomyolipoma (AML)

• clear cell "sugar" tumor of the lung

• lymphangioleiomyomatosis (LAM)

• clear cell myomelanocytic tumor (CCMMT)

  • of the falciform ligament / ligamentum teres

• unusual clear tumors of other organs

  • pancreas

  • rectum

  • abdominal serosa

  • uterus: considered one of the commonest sites of involvement in the female pelvis

  • vulva

  • heart

  • orbit

Epidemiology

PEComas are far more common in females ⁴. 

Associations

• tuberous sclerosis complex

Pathology

Microscopic appearance

All PEComas share similar and distinctive cellular morphology – peripheral epitheloid cells – which have no counterpart in normal tissue ⁴. These tumors appear as sheets and nests of epithelioid or spindle-shaped cells associated with blood vessel walls. They have granular eosinophilic cytoplasms. 

Immunophenotype

PEComas are characterized by immunoreactivity to smooth muscle and melanocytic markers ⁴.

• smooth muscle: actin, desmin

• melanocytic: HMB-45, melan-A

Radiographic features

Unfortunately, due to non-specific imaging appearances and the scarcity of reported cases, no specific imaging features are recognized. These lesions seem to usually be solid but can be centrally necrotic ^5-7. They generally demonstrate prominent contrast enhancement ⁶. 

Treatment and prognosis

PEComas usually behave in a benign fashion although local recurrence and even malignant behavior are encountered, mimicking malignant sarcomas. Surgical excision is usually curative. 

Differential diagnosis

The differential diagnosis is broad and largely depends upon the location of the mass.