A b s t r a c t 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, , 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

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... cinomas; most reactive neoplasms had CK7 staining of fewer than 25% of cells. CK20 had similar results. The percentage of PSA-and 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.