Giant Cell Tumor of Flexor Tendon Sheath: An Interesting Clinical Presentation as Subungual Growth

Giant cell tumor of tendon sheath (GCTTS), presenting as a subungual mass, is a diagnostic challenge and requires differentiation from other subungual tumors such as fibroma of tendon sheath and superficial acral fibromyxoma.

We describe a 32-year-old female patient with a relatively rare subungual presentation of GCTTS. The patient presented with slowly enlarging, painless subungual swelling over the dorsum of the right thumb, raising the proximo-lateral nail plate, extending under the proximal nail fold. The clinical, onychoscopic, radiological, and histopathological features of the case are described, which helped in confirmation of diagnosis and differentiation from other subungual tumors.

GCTTS can present as a diagnostic challenge due to its varied clinical manifestations, especially in the subungual location. A combination of clinical features and onychoscopy can point toward a diagnosis, which can be confirmed upon excision and histopathology.