Perivascular myoid tumors of the oral region: a clinicopathologic re‐evaluation of 35 cases

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Myopericytoma (MPC) is a generic denomination to describe tumors showing differentiation toward perivascular myoid cells /myopericytes. It has been suggested that MPC forms a morphologic continuum with glomus tumor (GT), solitary myofibroma (SMF), and angioleiomyoma (ALM). This proposed relationship has not yet been assessed in the oral region. We reviewed our 28-year experience with 35 oral tumors, originally diagnosed as ALM (n = 28), SMF (n = 4), GT (n = 2), and MPC (n = 1) to analyze their overlapping microscopic features, with the assistance of immunohistochemistry. Myopericytoma showed a wide range of growth patterns; concentric perivascular whorls, hemangiopericytomatous areas, glomangiopericytoma (GPC)-type vessels and leiomyomatous foci. Intravascular growth was also seen. Among 28 cases studied, three ALM were reclassified as MPC (n = 2) and SMF (n = 1), based on the present diagnostic criteria. Additional MPC-type components, at varying degrees, were similarly found in four ALM and three SMF, at least focally. One GT featured intravascular whorls of spindle cells. These four interrelated groups of tumors had in common GPC-type vasculature and intraluminal cellular proliferation was nearly ubiquitously present. Diffuse immunoreactivity for alpha-smooth muscle actin and less staining intensity of muscle-specific actin were observed in all tumors. Only ALM displayed desmin positivity of variable extent. Neither case tested expressed CD34. Our data matches with the recent results in extraoral sites that MPC, GT, SMF, and ALM exhibit histologic and immunohistochemical overlap with each other. A common perivascular myoid differentiation between these tumor types is further reinforced by the present oral series.