Immunohistopathologic variation of oral myopericytoma

Objective Myopericytoma (MP) is a rare soft tissue neoplasm infrequently arising in the oral cavity. We aimed to clarify the clinicopathologic characteristics of oral MP based on histologic and immunohistochemical findings. Methods We reviewed myogenic neoplasms in our archives and selected 6 cases of MP. Immunostainings were performed using antibodies for smooth muscle actin (SMA), calponin, h-Caldesmon, muscle-specific actin (MSA), desmin, and type IV collagen antibody. Results Our patients were predominantly female, and the mean age and size were 57.5 years and 10.8 mm, respectively. Histologically, 3 of 6 cases were well circumscribed but others showed ill-defined borders. Three cases were classic but others were angioleiomatous and myofibromatous cases with a mostly fascicular pattern. Myxoid change appeared in 2 cases. Hyalinized nodules (vascular balls) were found in both classic and nonclassic types. Only one case partially comprised small round cells mimicking glomus cells, but these lacked peculiar type IV collagen expression. Two angioleiomatous cases harbored dilated blood vessels. Two cases partially showed a staghorn and indistinct biphasic pattern but a myofibromatous type demonstrated neither. Immunohistochemically, all cases that tested were positive or focally positive for SMA, MSA, and calponin but negative tumor cells were noted in part. However, h-Caldesmon was only detected in 2 out of 5 cases examined. Desmin was constant-negative except for 1 classic case with focally positive reaction. Conclusion Oral MPs are morphologically and phenotypically heterogeneous neoplasms that can sometimes mimic angioleiomyoma or glomangioma. It is necessary to recognize the presence of cases showing varied myogenic natures.