Rectal examination in volume determination of carcinoma of the prostate: clinical and anatomical correlations.

A comparison was made between tumor area estimated on rectal palpation and actual tumor size calculated from the radical prostatectomy specimen in 17 patients with prostatic carcinoma. For each patient a diagram of the rectal examination findings was superimposed onto a histological reconstruction map of the surgical specimen, and relative areas were measured with a computer. In only 1 case was there close correlation between palpated and actual tumor area. Seven patients had actual tumor areas that were more than twice the palpated area. In 5 patients the palpated areas corresponded to foci of capsular involvement, while adjacent large areas of cancer abutting the capsule were not recognized. Discrepancies of this magnitude may result not infrequently in assignment of a clinical stage B1 to tumors that are histologically stage B2.