Giant thigh glomus tumor of uncertain malignant potential: Case report with pathologic–radiologic correlation

Glomus tumors (GT) are rare, benign tumors that arise from glomus bodies and usually develop in digital areas. Extradigital GT are exceptional and thigh location is infrequent.We report a case of a GT of the thigh in a 79-year-old male patient that measured 9.5 cm in maximum size. The GT lay above the muscular fascia without infiltrating it. Internal hypervascularity was seen by spectral Doppler ultrasound. Magnetic resonance image showed a heterogeneous mass with hyperintense and hypointense components and internal lobes with liquid-liquid levels. Histopathology revealed a monotonous round-cell proliferation with central nuclei without atypia or mitotic figures, around small-caliber vessels. These cells expressed smooth muscle actin and pericellular collagen IV. GT of uncertain malignant potential was diagnosed. The mass was completely removed. The patient did not experience local relapse nor distant metastasis.GT are rare soft tissue tumors whose diagnosis of unusual giant masses in uncommon locations may be delayed and misdiagnosed given the low suspicion.