Tendon sheath tumours: a pathological study of the relationship between giant cell tumour and fibroma of tendon sheath.

Thirty-nine soft tissue lesions occurring on the distal aspect of the limbs have been selected because of histological features consistent with those recognized for giant cell tumour of tendon sheath or fibroma of tendon sheath. In spite of the frequent occurrence of such lesions at the stated sites, they were rarely correctly diagnosed pre-operatively. Using a scoring system to grade specified histological features, a blind evaluation to re-classify these 39 lesions was undertaken. This resulted in 29 cases of giant cell tumour of tendon sheath, six fibromas of tendon sheath and four 'transitional stage' lesions. Despite the heterogeneous morphology of these categories, there were no significant differences in the clinical features of affected patients. The existence of a 'transitional stage' lesion, combined with the homogeneous clinical picture of all categories, supports the concept that fibroma of tendon sheath is the end and sclerosing stage of giant cell tumour of tendon sheath, probably consequent on progressive vascular impairment. There is a need for pathologists to recognize the transitional stage lesions so as to avoid their inclusion with other diagnostic entities. For this group the name 'giant cell tumour of tendon sheath--transitional stage lesion' is suggested.