2025 Volume 24 Issue 2 Pages 198-203
A 56-year-old Japanese man was referred to our hospital because of a subcutaneous nodule with significant tenderness on his left forearm that had developed 10 years earlier. His symptoms completely resolved with surgical treatment. Histopathological examination revealed glomus cells with round nuclei and acidophilic cytoplasm that were densely proliferating. Immunohistochemical staining revealed positivity for vimentin and α-SMA, and negativity for S-100 protein, desmin, and CD34. We diagnosed glomus tumor. Since glomus tumors typically arise in the subungual region, diagnosing them can be challenging when they occur in atypical locations outside of this area. The most common sites outside the subungual region are the arms (40%), legs (26%), and trunk (20%). Histopathologically, the subcutaneous nodule comprised two distinct tumor components : glomus tumor proper, which is predominantly composed of a proliferation of glomus cells ; and glomangioma, which is composed of a proliferation of dilated blood vessels. The present case represented a relatively rare case of a mixed-type tumor. Magnetic resonance imaging is a useful auxiliary diagnostic tool for glomus tumors. Therefore, if a patient experiences pain in subcutaneous soft tissues outside of the fingers, it is important to consider proactive imaging tests. Skin Research, 24 : 198-203, 2025
