Pericyte Antigen Expression In Human Perivascular Soft Tissue Tumors

Previous studies utilized perivascular- and pericytes-specific antigens to isolate perivascular stem cells from several human tissues, and found them capable of regenerating and differentiating into mesoderm derived tissues. However, pericyte and perivascular antigens have not yet been investigated in several soft tissue tumors that are thought to be of a perivascular or mesenchymal origin. In this project, immunochemical staining was performed on paraffin embedded slides of several types of human perivascular soft tissue tumors, including glomus tumor (n=10), angioleiomyoma (n=9) and myopericytoma (n=3). For a comparison the myoid-melanocytic tumor perivascular epithelioid cell tumor (PEComa) (n=16) and the fibroblastic tumor solitary fibrous tumor (SFT) (n=5) were also investigated. Antibodies against perivascular cell and pericyte markers included CD146, PDGFR-β and α-SMA. Results showed diffuse immunoreactivity for all pericyte markers in the related tumors glomus tumor, angioleiomyoma and myopericytoma. Specifically, CD146 showed immunoreactivity in 10/10 glomus tumors (100%), 9/9 angioleiomyoma (100%), and 3/3 myopericytoma (100%). Likewise, PDGFR-β showed immunoreactivity in 10/10 glomus tumors (100%), 5/9 angioleiomyoma (56%), and 3/3 myopericytoma cases (100%). α-SMA showed diffuse positivity in 10/10 glomus tumors (100%), 9/9 angioleiomyoma (100%), and 3/3 myopericytoma (100%). In marked contrast, essentially absent staining for all pericyte markers was observed in solitary fibrous tumor (SFT). Furthermore, a patchy and perivascular distribution of pericyte antigens was identified in PEComa specimens (11/16 for CD146 (69%), 13/16 for PDGFR-β (81%), and 13/16 for α-SMA (81%)). In summary, identification of diffuse immunoreactivity for pericyte antigens in a subset of soft tissue tumors suggests their pericytic differentiation, and points to their probable pericyte origins. SFT, once hypothesized as a pericyte-derived tumor, shows fibroblastic rather than pericytic differentiation. PEComa family tumors show scattered pericyte differentiation, which may reflect aberrant adoption of a pericyte-like phenotype among a neural crest cell population. Further immunophenotyping and characterizing soft tissue tumors may improve clinical diagnosis and treatment options.