Myxoid Glomus Tumors Showing CD34 Expression: A Series of Eight Cases

Background: Myxoid glomus tumors (mGTs) are an uncommon histologic pattern of glomus tumors, characterized by prominent myxoid stromal changes that may mimic a wide range of soft tissue neoplasms. Recent reports of unexpected CD34 expression in some cases have further complicated their differential diagnosis. Objectives: This study aimed to characterize the histopathological, immunohistochemical, and clinical features of cutaneous mGTs, with particular emphasis on CD34 expression. Methods: We analyzed 8 histologically confirmed cases of cutaneous mGTs underwent to a comprehensive evaluation of morphological features and immunophenotypic profile, with available clinical data. The immunohistochemical panel included smooth muscle actin (SMA), CD34, and S100. Mast cell density was assessed by tryptase in 3 cases. As controls, 8 glomus tumors without myxoid features were also examined for CD34 expression. Results: The cohort consisted of 8 patients (2 males, 6 females; age range 23-71 years). All tumors were located on the distal phalanges of the digits and showed extensive myxoid stromal changes. Immunohistochemistry demonstrated SMA positivity and CD34 expression in all mGTs. In contrast, none of the control GTs without myxoid stroma expressed CD34. Mast cells were consistently identified in the tested cases, predominantly within the myxoid matrix, suggesting a possible role in stromal remodeling. Conclusions: mGTs represent a rare but distinct histological pattern within the glomus tumor spectrum; frequent CD34 expression and mast cell infiltration appear to be characteristic features, although their biological significance remains uncertain. Recognition of these findings is essential to avoid misdiagnosis with other CD34-positive perivascular neoplasms or myxoid soft tissue sarcomas.