Fibroma of the tendon sheath - a rare hand tumor.

Fibroma of the tendon sheath (FTS) is a rare, benign, soft tissue lesion. Clinically, FTS presents similarly to the more common giant cell tumor of the tendon sheath. It is distinguished histologically by the lack of giant cells, foamy histiocytes and synovial cells. We presented a case of FTS involving the common tendon sheath surrounding the flexor tendons leading to the third metacarpal. A 63-year-old man presented with a 3-month history of a painless mass in his right palm that had recently tripled in size. Examination demonstrated a 5x4 cm firm, nodular, superficial mass that was adherent to the overlying skin. Radiographs of the hand revealed a soft tissue mass without bony abnormality. Ultrasound demonstrated a solid, heterogeneous and hypoechoic mass and computed tomography demonstrated that the mass centered predominantly at the mid and distal portions of the third metacarpal. The patient underwent excisional biopsy of the lesion and a palmar, longitudinal incision was made from the wrist to the third metacarpal. Submitted histologic sections revealed a well-circumscribed lesion closely resembling hyalinized collagen. Neither vascular proliferations, necrosis, nor mitoses were observed. Similarly, multinucleated giant cells, pigment-laden macrophages, and inflammatory cells were also not identified. A diagnosis of FTS was rendered. We provided an additional rare case to the literature of a FTS and highlight the need to consider this entity in the differential diagnosis for any soft tissue lesion in the hand. Three months post surgery the patient demonstrated full range of motion of the hand.