Fibroma of Tendon Sheath Revisited.

Fibroma of tendon sheath (FTS) is a benign fibroblastic/myofibroblastic neoplasm that primarily occurs in the fingers and hands of young and middle-aged adults. The lesion typically presents as a small, firm, slow-growing, painless nodule. Ultrasonography usually shows a focal nodular mass with homogeneous hypoechogenicity. Magnetic resonance imaging reveals a well-defined nodular mass with decreased signal on all pulse sequences. No or minimal peripheral enhancement is often seen after intravenous contrast. Histologically, the lesion is well circumscribed and consists of bland spindle cells in a dense collagenous stroma with slit-like thin-walled vessels at the periphery. A cellular variant of FTS has also been described and shows at least a focal morphological overlap with nodular fasciitis. Immunohistochemistry does not play a significant role in the diagnosis of FTS. Cytogenetic studies have demonstrated the presence of 11q rearrangements. A significant subset of cellular variants of FTS are characterized by ubiquitin specific peptidase 6 (USP6) rearrangements, with a variety of fusion partners. Complete surgical excision is the treatment of choice. This review provides an updated overview of the clinical, radiological, histological, cytogenetic and molecular genetic features of FTS and discusses the differential diagnosis of this uncommon entity.