Anatomic Pathology / IMMUNOPHENOTYPE OF INTERMEDIATE AND HIGH GLEASON SCORE PROSTATE ADENOCARCINOMAS Immunophenotypic Characterization of 225 Prostate Adenocarcinomas With Intermediate or High Gleason Scores

This study provides detailed staining results for 225 prostate adenocarcinomas, including 150 Gleason score 8, 9, and 10 adenocarcinomas with cytokeratins (CKs) 7, 20, 5/6, and 17, prostate-specific antigen (PSA), prostatic acid phosphatase (PAP), carcinoembryonic antigen (CEA), WT1, thyroid transcription factor-1 (TTF-1), and villin. CK7 was reactive in 112 adenocarcinomas (49.8%). The percentage of CK7-reactive adenocarcinomas and the percentage of CK7-stained cells increased in higher Gleason score adenocarcinomas; most reactive neoplasms had CK7 staining of fewer than 25% of cells. CK20 had similar results. The percentage of PSAand PAP-reactive adenocarcinomas and the percentage of stained cells in reactive neoplasms decreased in higher Gleason score adenocarcinomas. CK5/6 and CK17, WT1, CA-125, TTF-1, and villin were nonreactive. The prostate can be the primary site of metastatic adenocarcinoma that is nonreactive for PAP and PSA and has CK7 or CK20 reactivity in fewer than 50% of the cells. The likelihood that a metastatic adenocarcinoma is from the prostate is low if reactivity with any of the cytokeratin antibodies, CEA, TTF-1, CA-125, WT1, or villin is extensive. The prostate often is included in the list of possible primary sites of metastatic and poorly differentiated adenocarcinomas. Immunohistochemical analysis often can identify the primary site or shorten the list of possible primary sites. In addition to cytokeratin 7 and 20 antibodies, which are frequently on the roster of tumor-identification antibody panels, several recently introduced antibodies seem to be useful additions. There is limited or no staining experience with these antibodies, including cytokeratin 7 and 20 in intermediateand high-grade prostate adenocarcinoma. The goals of this study were to characterize the immunoreactivity and to provide detailed staining results in prostate adenocarcinomas with intermediate and high Gleason scores with the antibodies that are used commonly in tumor-identification antibody panels. These results provide a comparative framework for determining the likelihood of whether a metastatic or poorly differentiated adenocarcinoma is from the prostate. Materials and Methods Whole-mount slides of 225 radical prostatectomies with large volume adenocarcinomas with homogeneous Gleason scores were randomly selected based on their Gleason score from the files of William Beaumont Hospital, Royal Oak, MI, during the period January 1989 through December 2000. A region of abundant adenocarcinoma with homogeneous Gleason scores was circled on a whole-mount slide from each case, and regular-sized slide sections were cut from these areas for immunohistochemical staining. The minimum diameter of the circled regions was 1.8 cm. Twenty-five Am J Clin Pathol 2002;117:471-477 471 © American Society for Clinical Pathology Goldstein / IMMUNOPHENOTYPE OF INTERMEDIATE AND HIGH GLEASON SCORE PROSTATE ADENOCARCINOMAS adenocarcinomas (11.1%) were Gleason score 6, 50 (22.2%) were Gleason score 7, 54 (24.0%) were Gleason score 8, 58 (25.8%) were Gleason score 9, and 38 (16.9%) were Gleason score 10. Fourteen adenocarcinomas had a significant large duct component, including the large ducts of the verumontanum. Four were Gleason score 7 (4 + 3), 7 were Gleason score 8, and 3 were Gleason score 9. All 14 neoplasms were peripheral zone–predominant adenocarcinomas. Immunohistochemical Analysis Consecutive 3-μm-thick sections were cut from the circled area of the whole mount block, and each section was placed on charged slides. Sections were deparaffinized, immersed in EDTA buffer (pH 7.0), and placed in a commercial vegetable steamer at 95°C for 30 minutes. They were transferred to a commercial immunohistochemical autostainer (DAKO, Carpinteria, CA), and the primary antibody was incubated over the sections for 20 minutes. The Envision-plus (DAKO) detection system was used. ❚Table 1❚ lists the primary antibodies used in the study. A positive control slide containing known cytokeratinreactive nonprostatic tissues was included with each batch of simultaneously stained slides. All of the cases had at least 1 negative control slide that was run parallel with a test slide in which the primary antibody step was omitted. Cytokeratin AE1/AE3 served as a “fixation” control and was diffusely and strongly reactive in all 225 adenocarcinomas. The percentage of moderately or strongly reactive invasive adenocarcinoma cells in each case was quantified and tabulated as follows: 0%, fewer than 5%, 5% to 25%, 26% to 50%, 51% to 75%, and more than 75%. Reactivity of fewer than 5% of the adenocarcinoma cells was rare, individual stained cells, constituting no more than 1 cell in a medium magnification field using the 10× objective. Reactivity in the 5% to 25% group was either an individual cell pattern of several cells per 10× field or widely dispersed small cell groups of reactive cells with a density of no more than 1 per 10× field. Reactivity of 26% to 50% had the appearance that a minority of cells were reactive at low magnification. At higher magnification, the pattern of reactivity was patchy or homogeneous. Patchy reactivity was extensive reactivity in a region of the slide while other regions were nonreactive. The homogeneous pattern was small groups of usually fewer than 5 reactive cells interspersed among nonreactive cells. Reactivity of 51% to 75% was similar to the 25% to 50% group except that reactive cells were clearly predominant. The group with more than 75% reactivity had the appearance of unquestionable reactivity in the overwhelming majority of cells. Borderline cases between the 26% to 50% and the 51% to 75% reactivity groups were classified on the low-power magnification appearance of whether reactive or nonreactive cells constituted the major population. Borderline cases between the 51% to 75% and more than 75% reactivity groups were classified based on the low-power magnification appearance of whether the reactive cells constituted a slight or dominant majority of cells.