Phenotypic characterization of perivascular myoid cell neoplasms, using myosin 1B, a newly identified human pericyte...

Our aims were to identify pericyte-specific markers for the analysis of formalin-fixed, paraffin-embedded human tissue samples, and to characterize perivascular myoid cell neoplasms phenotypically. Previously identified pericyte markers failed to distinguish pericytes from other cellular types, such as vascular smooth muscle cells (vSMCs) and fibroblasts, in immunohistochemistry analysis. However, we compared gene expression profiles between pericytes, vSMCs, and fibroblasts, and performed human skin vasculature immunohistochemistry analysis, which led to the identification of myosin 1B (MYO1B) as a novel pericyte marker. Afterward, we investigated the expression levels of MYO1B and h-caldesmon (h-CD) in perivascular myoid cell neoplasms, angioleiomyomas (n=28), glomus tumors (n=23), and myopericytomas (n=3). Angioleiomyomas were shown to contain MYO1B-negative and h-CD-positive (MYO1B^-hCD⁺) tumor cells, with vSMC features. Glomus tumors were predominantly composed of the MYO1B⁺hCD⁺ tumor cells, with the intermediate features between pericytes and vSMCs, whereas MYO1B⁺hCD^- tumor cells with pericytic features and/or the MYO1B^-hCD⁺ tumor cells with vSMC features were frequently found in these tumors. The perivascular concentric pattern of 2 myopericytoma cases was composed of MYO1B⁺hCD⁺ tumor cells, whereas that of one myopericytoma contained MYO1B^-hCD⁺ tumor cells. These results indicate that the ability to distinguish between these cell types may allow us to understand the differentiation and origin of perivascular myoid cell neoplasms. This is the first study to identify cell properties of perivascular myoid cell neoplasms by using a pericyte-specific marker with considerably lower expression in vSMCs and fibroblasts.