MORPHOLOGICAL AND IMMUNOHISTOCHEMICAL FINDINGS OF UNUSUAL ORAL MESENCHYMAL TUMORS

Abstract

<h3>Objectives</h3> To evaluate the features of uncommon oral benign and malignant tumors of fibroblastic, myofibroblastic, and fibrohistiocytic origin to better understand the diagnostic challenges of these tumors. <h3>Study Design</h3> This study evaluated benign fibrohistiocytic tumor (BFH; <i>n</i> = 4), myofibroma (MF; <i>n</i> = 2), solitary fibrous tumor (SFT; <i>n</i> = 6), fibrosarcoma (FS; <i>n</i> = 2), dermatofibrosarcoma protuberans (DFSP; <i>n</i> = 1), and myofibroblastic sarcoma (MFS; <i>n</i> = 1) obtained from a diagnostic service. We carried out morphologic and immunohistochemical (αSMA, vimentin, desmin, CD34, Bcl2, S100, CD68, CD99) analyses. <h3>Results</h3> Morphologic analysis showed several features in tumor cells and stroma of the tumors (multinucleated cells, clear cells, hypercellular and hypocellular areas). Immunohistochemistry demonstrated that all cases were positive for vimentin and negative for desmin. BFH tumors exhibited immunopositivity for CD68 and S100, whereas MFs were positive for αSMA and SFTs for CD34, CD99, and Bcl2. Regarding malignant tumors, DFSP was positive for CD34 and Bcl2, and MFS was positive for αSMA and Bcl2, whereas FS was negative for most of the antibodies analyzed. Furthermore, malignant tumors exhibit a higher proliferation index (Ki-67 > 10%). <h3>Conclusions</h3> Considering their morphologic similarity, the use of immunohistochemistry is of great value to help in the differential diagnosis of these tumors.