Objective: Among prostatic lesions with atypical features, atypical adenomatous hyperplasia (AAH; microglandular proliferation with bland nuclei), and prostatic intraepithelial neoplasia (PIN; cellular atypia in preexisting large ducts and acini) are considered precursors of prostatic cancer, but these lesions are a continuum from the normal prostate to prostatic cancer. The objective of the paper is to bring attention to the pitfalls in the diagnosis of both lesions.
Material and methods: To describe the diagnostic limits in AAH and PIN, we used the literature information and our 76 cases of AAH and 169 patients with PIN at prostatic core biopsy.
Conclusions: In the majority of cases, AAH appears in the transition zone and it is necessary to be very strict in the diagnosis in order to avoid confusion with microglandular BPH. One of the controversies is the biologic significance of prominent nucleoli in the AAH. Although the association of AAH with cancer is relatively scant, we have a higher incidence of cancer in cases with AAH than in classic BPH and we recommend complete study of the surgical specimen. Low-grade PIN does not need to be reported, but high-grade PIN should be and close follow-up is recommended if we find an isolated high-grade PIN. Because the clinical implications of high-grade PIN are so important, pathologists must be sure of the diagnosis avoiding interpretation in inflammatory areas. The high-molecular-weight cytokeratins may be useful in some cases, when the diagnosis of adenocarcinoma vs. high-grade PIN is seriously considered.