The diagnosis of soft tissue tumours.

We prospectively analysed methods of diagnosis in 118 patients referred for definitive treatment with documented or presumed soft tissue sarcoma (STS). Of 65 patients with primary STS, 54 were biopsied before referral. Of these, 5 (9%) were biopsied by Tru-cut biopsy, 17 (32%) by incisional biopsy and 32 (59%) by excisional biopsy. The remaining 11 patients with primary STS, referred without biopsy, were all diagnosed by Tru-cut biopsy. An additional eight patients suspected of having STS were referred without biopsy and were found to have malignant tumours other than STS involving soft tissue by Tru-cut biopsy. Nineteen patients were proved to have benign soft tissue tumours; in 13 presumed to have STS, the diagnosis was unknown at referral. In four of these, biopsy was inappropriate. Of nine submitted to Tru-cut biopsy, an unequivocal diagnosis was made in 5 (56%) and incisional biopsy was required in the other four. Therefore, paradoxically, benign soft tissue tumours may be more difficult to diagnose with Tru-cut biopsy than malignant tumours. This study confirms the high degree of accuracy of Tru-cut biopsy in diagnosing malignant soft tissue tumours and highlights the disadvantages of open biopsy techniques.