Prostatic 'capsule'--a comparative study of histological and ultrasonic appearances.

The histological and transrectal ultrasound (TRUS) appearances at corresponding sites of the periphery of the prostate gland have been compared in 30 benign and 27 malignant glands taken at autopsy. In the benign series, the histological capsule was frequently absent and correlated poorly with the consistent TRUS findings of a regular, well-defined 'ultrasonic capsule'. It is concluded that 'the capsule' should be replaced as a tumour-staging landmark by a more realistic terminology. Carcinoma may be described as intra- or extra-prostatic, or confined or unconfined with respect to the gland. In the malignant glands, there was no correlation between morphologically unconfined cancers and irregular or absent ultrasound 'capsule' when corresponding areas were compared. This disparity must contribute to an underestimation of tumour extent with TRUS.