Heterogeneity of Gleason grade in multifocal adenocarcinoma of the prostate

Abstract

Background: The Gleason grading system uniquely combines data from different areas of carcinoma in the same prostate specimen. Prostatic adenocarcinoma often is multifocal, and different Gleason grades may be present in different foci. The current study was undertaken to compare the Gleason grades of individual adenocarcinoma foci in a given specimen with the overall Gleason grades (primary and secondary) of that specimen.

Methods: Data were obtained from 115 consecutive radical prostatectomy specimens via whole-mount processing and complete sectioning. Diagrams were constructed by tracing the outline of each whole-mount section, and tumor maps subsequently were generated. The largest focus was considered the index tumor. Each prostatectomy specimen was assigned primary and secondary Gleason grades, and each tumor focus was assigned its own primary and secondary Gleason grades. Tumor volume was measured using the grid method.

Results: Two or more adenocarcinoma foci were present in 87% of all specimens (2 foci, n = 20; 3 foci, n = 33; 4 foci, n = 17; 5 foci, n = 13; > 5 foci, n = 17). Specimens (n = 15) containing a single tumor were excluded from further analysis. Among the remaining specimens (n = 100), all tumor foci had Gleason grades that were the same as the corresponding overall Gleason grades in only 9 cases (9%). The Gleason score (i.e., the sum of the primary and secondary grades) of the index tumor was correlated with the overall Gleason score in 68% of specimens. The primary grade of the index tumor was the same as the overall primary grade in 97 specimens, whereas the secondary grade of the index tumor was the same as the overall secondary grade in only 68 specimens. The primary and secondary grades of the index tumor, compared with the overall Gleason primary and secondary grades, were reversed in 17 specimens.

Conclusions: The findings of the current study demonstrated the histologic heterogeneity of multifocal prostate malignancies. Although the Gleason grading system was used to determine an overall score for prostate carcinoma within a specimen, the scores of individual tumors, including index tumors, often did not agree with this overall score. These findings may have implications with respect to future biomarker and tissue array studies.