Abstract
<h3>Background</h3> In 1996, an unusual oral lesion was described as epithelioid leiomyoma featuring epithelioid and spindle cells that expressed smooth muscle actin (SMA) and selectively desmin (DES). <h3>Objectives</h3> To revisit the morphologic properties of such lesions given (a) the availability of novel and more specific smooth muscle markers and (b) the significant advances made in the characterization of myofibroblasts. <h3>Methods</h3> Two examples were studied that presented as hyperplastic polyps on the buccal mucosa of 2 female patients (38 and 80 years old). Immunohistochemical evaluation was performed for SMA, DES, calponin (CALP), smooth muscle myosin (SMM), h-Caldesmon(h-CALD), smoothelin (SMOO), MyoD1, myogenin (MYOG), collagen type IV (COLIV), laminin (LAM), CD68, and CD34. <h3>Results</h3> The lesions were characterized by 2 cell types: (a) epithelioid cells with eosinophilic, granular, or clear cytoplasm and (b) elongated spindle cells with eosinophilic cytoplasm showing spindle tapered nuclei. The stroma was fibromyxoid and vascular. Cells of interest were highlighted and equally decorated by SMA, CALP, and SMM. DES, h-CALD, and SMOO identified fewer spindle and epithelioid cells with these 3 antibodies decorating the same cell population, which also exhibited collagen type IV and LAM positivity. MyoD1, myogenin, and CD34 were negative. CD68 highlighted few spindle and epithelioid cells, suggesting the presence of lysosomes. <h3>Conclusions</h3> Based on advances in the study of myofibroblasts, the present findings confirm the capability of myofibroblasts to attain or transform into smooth muscle properties. The present cases are reactive myofibroblastic lesions with transformation of some cells into smooth muscle cells. The term epithelioid leiomyoma is not favored.
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