Track: Case Reports

Abstract:

Glomus tumors are rare mesenchymal neoplasms composed of cells resembling the glomus body. While typically benign, these tumors have the potential to undergo malignant transformation. Malignant glomus tumors of a cutaneous origin are exceedingly rare, and the genetic changes underlying the malignant potential remain poorly understood. We report a case of a 38-year-old man who presented with a large painful violaceous plaque with central hemorrhagic crust on the left flank. Punch biopsy revealed a dermal neoplasm with features of a glomus tumor, but with increased nuclear atypia, crowding, and mitoses (6/10 high-power fields[HPF]). Lesional cells were positive for smooth muscle actin(SMA). Collagen IV showed patchy weak-to-moderate pericellular staining. They were negative for D2-40, desmin, HHV8, and cytokeratin AE1/3. C-MYC showed weak patchy nuclear staining, and Ki-67 revealed a proliferative index of approximately 10%. According to an analysis of 52 reported cases in the literature, histologic criteria for malignancy include the presence of atypical mitotic figures or the combination of moderate-to-high nuclear grade and mitotic activity (>5 mitoses per 50HPF). Based on these published criteria, this case meets threshold for malignancy. Malignant glomus tumors have a reported metastatic rate of up to 38%, which carries poor prognosis. Early recognition is critical for appropriate surgical intervention and management of this tumor. This case highlights the need for increased awareness of malignant glomus tumors. It is crucial to perform careful histopathologic evaluation of glomus tumors to detect any potential cytologic atypia and mitotic activity to accurately diagnose and manage these exceedingly rare neoplasms.