A simple technique for calculation of the volume of prostatic adenocarcinomas in radical prostatectomy specimens

Tumor volume has been suggested as an important prognostic factor of prostatic adenocarcinoma (PAC) treated with radical prostatectomy (RP). The calculation of tumor volume is complicated by the difficulty in appreciation of tumor nodules at gross examination, multifocality, and variation in the shape of tumor nodules. We propose a simple technique for the calculation of tumor volume. One hundred consecutive specimens of RP were studied with special attention to the shape of tumor nodules. Most small PAC, transitional zone (TZ) PAC, peripheral zone (PZ) PAC without associated benign prostatic hyperplasia (BPH), and PZPAC with Gleason's score (GS) > 3 + 4 had an ovoid shape. Most large sized nodules of PZPAC with GS < 4 + 3 tended to mold according to the boundaries of the TZ that were themselves often compressed by hyperplastic nodules. Therefore, these large tumor nodules were crescentically shaped and had tapering pole(s). We deduced from that tendency that the ratio of height of the tumor nodule = D1 x the height/greatest horizontal diameter of the prostate (D1 = the greatest diameters of the largest section of tumor nodule). Using the mathematical formula for volume of an ellipsoid structure, we propose the following formula to calculate the volume of each tumor nodule = 0.8 x K x D1(2)x D2 (D2 = greatest diameter orthogonal to D1, and K = coefficient for correction of tumor volume due to the compression of hyperplastic nodules). K is empirically estimated as 2/3 for PZPAC in mid prostate and 1/2 for tumor nodules at the apex and base. The total tumor volume is the sum of all tumor nodule volumes. By measuring the two greatest orthogonal diameters, D, and D2, of the largest horizontal section of a tumor nodule, we were able to calculate the corresponding volume and consequently the total tumor volume of the prostate. Analysis of the calculated total tumor volume showed a good correlation with the current technique of measurement on each section of the prostate, particularly for tumors ranging from 1.5 to 3.0 cm3.