Archives of Pathology and Laboratory Medicine, vol. 132, issue 9 (2008) pp. 1388-1396
● Context.—The unrelenting challenge encountered when differentiating limited-volume prostate carcinoma and sometimes subtle variants from its many morphologic mim-ics has increased the use of ancillary immunohistochem-istry in routine prostate needle biopsies. The availability of prostate cancer–associated and basal cell–associated markers has been an invaluable addition to diagnostic sur-gical pathology. Objective.—To review commonly used immunohisto-chemical stains, including innovative combinations, for confirmation or differential diagnosis of prostate carcino-ma, and to propose appropriately constructed panels using morphologic patterns in prostate needle biopsies. Data Sources.—These best practices are based on our experience with routine and consultative case sign-outs and on a review of the published English-language litera-ture from 1987 through 2008. Conclusions.—Basal cell–associated markers p63, high-molecular-weight cytokeratin 34␤E12, cytokeratin 5/6 or a cocktail containing p63 and high-molecular-weight cytoker-atin 34␤E12 or cytokeratin 5/6 and prostate carcinoma–spe-cific marker ␣-methylacyl coenzyme A (coA) racemase alone or in combination are useful adjuncts in confirming prostatic carcinoma that either lacks diagnostic, qualitative or quantitative features or that has an unusual morphologic pattern (eg, atrophic, pseudohyperplastic) or is in the setting of prior treatment. The combination of ␣-methylacyl coA racemase positivity with negative staining for basal cell–as-sociated markers supports a malignant diagnosis in the ap-propriate morphologic context. Dual chromogen basal cell– associated markers (p63 [nuclear] and high-molecular-weight cytokeratin 34␤E12/cytokeratin 5/6 [cytoplasmic]) and ␣-methylacyl coA racemase in an antibody cocktail pro-vide greater sensitivity for the basal cell layer, easing eval-uation and minimizing loss of representation of the focal area interest because the staining is performed on one slide. In the posttreatment setting, pancytokeratin facilitates de-tection of subtle-treated cancer cells. Prostate-specific an-tigen and prostatic acid phosphatase markers are helpful in excluding secondary malignancies involving the prostate, such as urothelial carcinoma, and occasionally in excluding nonprostatic benign mimickers, such as nephrogenic ade-noma, mesonephric gland hyperplasia, and Cowper glands. There is no role for ordering immunohistochemistry pro-spectively in all cases of prostatic needle biopsies.
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