A rare cause of carpal tunnel syndrome: Fibroma of the tendon sheath

A fibroma of tendon sheath (FTS) is most commonly found in the hand. FTSs are usually seen in the fingers after the age of fifty and are clinically slow-growing well-defined mass. Here, we report the case of a 26-year-old man who featured a compression of the median nerve at the carpal tunnel secondary to a FTS of the flexor digitorum superficialis. Fibromas of a tendon sheath that compress the median nerve (MN) are rare causes of carpal tunnel syndrome (CTS). The patient was admitted with chief complaints of a growing bulge, numbness and pain in the left palm for 6 months (Figure 1A). There was a history of wrist fracture w8 months prior. Upon examination of the left-hypothenar region, a nonmobile, solid mass was detected, with no associated edema, erythema, or increased warmth. Following magnetic resonance imaging (MRI) the diagnosis of a regular soft-tissue mass under the hypothenar muscle, which was applying pressure to the carpal tunnel (Figure 1B) was suspected. Neurological and vascular examinations were unremarkable, and electrophysiological studies were not performed. The mass was totally excised under regional anesthesia. Macroscopically, the tumor was a smooth, dense, well-circumscribed, multinodular mass (Figure 1C). Final histological examination showed a circumscribed and lobulated hypocellular mass containing dense fibrocollagenous stroma with scattered spindleshaped fibroblasts without inflammatory cells. Narrow, slit-like vascular spaces were also present (Figure 1D). These histological findings were diagnostic of FTS. There were no operative or postoperative complications, and after surgery, the patient’s complaints of pain and numbness passed. Two years later, the patient remained free of symptoms and showed no recurrence.