Morphology of prostate cancer: the effects of multifocality on histological grade, tumor volume and capsule penetration.

A series of 151 radical prostatectomy specimens were subjected to whole-mount analysis. Features examined included histological grade, tumor volume, pathological stage and multifocality. Only 43.7% of the prostates contained a single carcinoma, 31.1% had 2 separate foci and the remaining 25.2% contained 3 to 6 tumors. Multifocality was greatest among tumors with the lowest mean volumes. Tumors with volumes of less than 3 cc were found in all grades (Gleason sums of 2 through 10). The highest volume tumors were those of intermediate grade (Gleason sums 4 through 8). Among tumors with volumes of less than 1 cc 70% that were confined within the prostatic capsule had Gleason sums of 4 or less. However, tumors with volumes of less than 3 cc that had invaded through the prostatic capsule were nearly equally divided between Gleason sums of 2, 3 or 4 and those of 5, 6 or 7. While studies examining the largest tumor per prostate have suggested that histological grade and volume are closely related, our results indicate that this is not necessarily the case. Furthermore, it is clear that tumors need not acquire either large volume or high grade before they can become locally invasive. It is likely, therefore, that the prediction of prognosis for patients with prostatic cancer is greatly influenced by tumor multifocality.