Expression of CD44 and CD29 by PEComa cells suggests their possible origin of mesenchymal stem cells.

BACKGROUND Perivascular epithelioid cell tumor (PEComa) is a rare mesenchymal tumor composed of histologically and immunohistochemically distinctive perivascular epithelioid cells. The perivascular epithelioid cell (PEC) co-expresses melanocytic and muscle markers. Since no normal counterpart to the PEC has ever been identified in any normal tissue, the cell origin of these tumors is still uncertain. Although, several hypotheses have recently been advanced to explain the histogenesis of PEComa, it remains unclear. METHODS The aim of this study was to discuss whether differential expression of stem cell-associated proteins could be used to aid in determining the histogenesis of PEComa. For this purpose, we detected the immunoexpression of 5 kinds of stem cell markers on PEComas, including CD29, CD44, CD133, ALDH1, and nestin. In addition to observed histopathologic morphology, we also performed PEComa relevant clinical diagnostic markers (HMB-45, SMA, melan-A, Desmin, Ki-67, S-100 and TFE3) to identify whether they belonged to PEComas. RESULTS Our study included 13 PEComa samples, and we obtained positive immunoexpression results as follows: CD29 (13/13), CD44 (8/13), ALDH1 (10/13), nestin (1/13), and CD133 (0/13). CONCLUSIONS Since CD44 and CD29 are surface proteins associated with MSCs, these results suggest that PEComa might arise from MSCs. However, whether MSCs are the origin of PEComa needs to be further explored in the future.