The significance of atypical adenomatous hyperplasia and prostatic intraepithelial neoplasia for the development of prostate carcinoma. An update.

The term prostatic intraepithelial neoplasia (PIN) is an accepted diagnosis in pathology of the prostate. The diagnostic difference between atypical adenomatous hyperplasia (AAH) and adenosis is still under debate. A number of questions remain about the significance of grading of AAH and PIN, the biology of AAH and PIN as precursors of carcinoma, the possibility of treatment of AAH and PIN and whether AAH- and PIN-associated cancers differ from non-associated carcinoma. This paper reviews the results and discussions at the First International Consultation Meeting on Atypical Adenomatous Hyperplasia and Prostatic Intraepithelial Neoplasia and the Origins of the Prostatic Carcinomas. AAH is an architectural atypia of the prostate. The histological and cytological features of AAH are intermediate between BPH and low-grade carcinoma of the prostate. Cell kinetic findings show no distinct neoplastic pattern. AAH may be a precursor of transition zone carcinoma but the findings to date are inconclusive. Follow up studies should address whether the association of AAH and carcinoma is incidental or whether transition occurs between AAH and carcinoma. In contrast, PIN is an accepted preneoplastic lesion and the most likely precursor of the dorso-peripheral zone carcinoma. The diagnosis of high-grade PIN is clinically important, because high-grade PIN is associated with carcinoma in a high percentage of patients (38-100%). AAH- and PIN-associated cancers may not differ from other prostatic cancers. At present treatment for AAH and PIN without carcinoma is not indicated, but high-grade PIN warrants surveillance and follow up of the patient to identify a possible coexisting cancer. It must be stressed that AAH and PIN are multifocal lesions and both are age-associated.