[Differential diagnosis of prostate cancer: impact of pattern analysis and immunohistochemistry]

Prostate cancer offers a wide range of growth patterns depicted in the classical Gleason diagram. For each Gleason pattern exist a number of benign and malignant mimickers that can simulate prostatic adenocarcinoma. In the present review, the use of immunohistochemical markers is discussed with emphasis to a pattern-based approach to differential diagnosis in prostate pathology. Basal cell markers (34betaE12 and P63) are very useful to analyze histo-architectural features of small and large glandular lesions. AMACR (P504 s) is helpful not only in identifying small amount of cancer in needle biopsies but also in the diagnosis of high grade prostatic intra epithelial neoplasia (HGPIN). A number of lesions which may be confused with small acinar adenocarcinoma (Cowper's gland, nephrogenic metaplasia, mesonephric glands) and poorly differentiated prostate cancer (urothelial neoplasia, mucinous colon cancer and other metastatic lesions) lacks convincing PSA immunoreactivity. Basal cell markers and the nuclear androgen receptors are important markers to differentiate Gleason grade 5 A und 5 B patterns from prostatic involvement by transitional cell carcinoma. Finally, a selected panel of markers is useful to classify prostatic stromal lesions. In each case, immunohistochemical findings should be interpreted in context with the various patterns on routine microscopy.