Utility of immunohistochemical detection of high molecular weight cytokeratin for differential diagnosis of proliferative conditions of the prostate

Background: Differential diagnosis of adenocarcinoma from other proliferative conditions in the prostate is often problematic. Immunohistochemistry using an antibody (34βE12) to high molecular weight cytokeratin, specifically present in basal cells of the prostate, could clearly demonstrate the presence or absence of these cells in the proliferating glands and thus provide an important clue in cancer diagnosis. Methods: To examine the utility of immunostaining using 34βE12, we examined 88 equivocal lesions. Twenty lesions with apparently benign and malignant features were added as controls. We compared the morphologic features of these lesions with their immunoreactivities toward 34βE12 on a personal computer display following storage on the MICROPHOT-FXA system. Results: Proliferating glands in all 20 benign lesions had 34βE12-reactive basal cells, but none of the malignant lesions did. The equivocal lesions were categorized on morphologic grounds into 2 groups: possibly benign and possibly malignant. Forty-five (51.1%) of the 88 equivocal lesions, were positive for 34βE12. These included 35 of the 45 (77.8%) possibly benign lesions and 10 of the 43 (23.3%) possibly malignant lesions. Among the equivocal lesions, 10 considered possibly benign on morphologic grounds showed negative reactivities, and 10 considered possibly malignant showed positive reactivities. Even through comparison on the computer display, no difference in morphology could be discovered between the negative and positive lesions in either group. Conclusion: Immunohistochemical procedures using 34βE12 are indispensable in the diagnosis of equivocal prostate lesions.