[Tendon sheath fibroma. A case report with immunohistochemical studies]

This report describes a 50-year-old male patient with fibroma of tendon sheath. The tumour had grown rapidly, and clinical examination of it led to the suspicion of a giant cell tumour of tendon sheath and a vascular glomus tumour. Microscopical investigation then allowed diagnosis of the tumour as a fibroma of tendon sheath, which was characterized by spindle-shaped and stellate-shaped fibroblasts, a fibrocollagenous, partly myxoid stroma, and slit-like vessels. Immunohistochemically, most tumour cells expressed vimentin and smooth muscle actin, but not desmin. Thus, fibroma of tendon sheath can be regarded as a synovial tumour with myofibroblastic differentiation. Histologically, fibroma of tendon sheath must be differentiated from other tumours, such as giant cell tumour of tendon sheath and histiocytoma, but also from nodular fasciitis and sarcomas.