PEComa

Overview
In oncology, PEComa, also PEC tumour and perivascular epithelioid cell tumour, is a type of mesenchymal tumour consisting of perivascular epithelioid cells (PECs).

Histologic appearance
PECs consist of perivascular epithelioid cells with a clear/granular cytoplasm and central round nucleus without prominent nucleoli.

Immunohistochemical markers
PECs typically stain for melanocytic markers (HMB-45, Melan A (Mart 1), Mitf) and myogenic markers (actin).

PECs and other conditions
PECs bear significant histologic and immunohistochemical similarity to: Thus, it has been advocated that the above could be classified PEComas.
 * angiomyolipoma,
 * clear-cell sugar tumour (CCST),
 * lymphangioleiomyomatosis, and,
 * clear-cell myomelanocytic tumour of ligamentum teres/falciform ligament.

Etiology
The precursor cell of PEComas is currently unknown. Genetically, PECs are linked to the tuberous sclerosis genes TSC1 and TSC2.