Fibroma of tendon sheath. A clinicopathologic study of 32 cases

We report 32 cases of fibroma of tendon sheath. Most cases presented as a painless mass in the distal portion of an extremity. Ganglion cyst was the most frequent clinical diagnosis. The median patient age was 30.5 years, and 60% of the patients were male. Only one lesion is known to have recurred. The lesions, which averaged 1.5 cm, were light tan, firm, and nodular. Histologic features common to all lesions were (a) a predominantly fibrous matrix containing (b) fibroblast-like spindle cells. Elongated, slitlike spaces were observed in many lesions, and nine cases had areas closely resembling nodular fasciitis. Myofibroblasts and fibroblasts were observed in the three cases studied by electron microscopy. The histologic findings were similar to those previously described for fibroma of tendon sheath. Although slitlike spaces are present in most instances, this finding is not specific for fibroma of tendon sheath, nor is it invariably present. Fasciitis-like changes have been noted in previous series. Our findings, as well as those from prior studies, indicate that fibromas of tendon sheath are heterogeneous. The diagnosis is made only after other fibrous, nodular lesions of the extremities are excluded. Fasciitis-like lesions heretofore classified as fibroma of tendon sheath are more appropriately classified as tenosynovial counterparts of nodular fasciitis.