Use of Immunohistochemistry as an Adjunct in the Diagnosis of Limited Adenocarcinoma of the Prostate Cancer

• The use of immunohistochemistry for basal cell markers and AMACR for the diagnosis of limited adenocarcinoma of the prostate should be used as an adjunct to the H&E diagnosis as there is false positive and negative staining with these markers. • Examples of labeling of prostate adenocarcinoma with basal cell markers include: aberrant scattered HMWCK staining of cancer cells; rarely the retention of a basal cell layer in carcinoma; and diffuse expression of p63 in some prostate cancers. • Basal cell markers are useful in distinguishing mimickers, such as adenosis, atrophy, radiation changes, and sclerosing adenosis, from prostatic adenocarcinoma recognizing that in some cases the staining pattern between mimickers and prostate carcinoma overlap. • Basal cell stains are helpful but are associated with pitfalls in the diagnosis of HGPIN and its distinction from carcinoma, PIN-like ductal adenocarcinoma, and intraductal carcinoma. • Although the vast majority of prostate adenocarcinomas label with antisera to PSA, there are some that are negative where the P501S (prostein) and PSMA (prostate specific membrane antigen) may be positive. • Other examples of useful immunohistochemistry include stains for CD68 to distinguish prostatic xanthoma and nonspecific granulomatous prostatitis from high grade prostate cancer.