Adenosis / Atypical adenomatous hyperplasia of Prostate Gland. Review and Update
Authors: Kodzo-Grey Venyo Anthony 
Published: February 2025

The diagnosis of carcinoma of prostate gland has tended to be challenging because of the existence of lesions that simulate adenocarcinoma of prostate gland. Such a type of prostate lesion is atypical adenomatous hyperplasia (AAH) or adenosis, which represents a proliferation of crowded, small to medium glands with basal cell layer invariably present, but often it has tended to inconspicuous upon routine histopathology of prostate gland examination staining. The importance of the lesion lies in its potential for being misdiagnosed as low-grade adenocarcinoma (Gleason 1 or 2). Atypical adenomatous hyperplasia (AAH) or adenosis of the prostate gland is terminology that is used for a pseudo-neoplastic lesion which can simulate adenocarcinoma of prostate gland in view of its cytological as well as its architectural features. It had previously been iterated that for many years, atypical epithelial lesions of the prostate gland had been known to occur, but much refining of this knowledge had eventually evolved over the last three and half decades. Previously two lesions, prostatic intraepithelial neoplasia (PIN) and AAH, were regarded to be precursors of adenocarcinoma of prostate gland. Nevertheless, PIN has now remained the only well-proven preneoplastic condition with clinical significance. It had been pointed out that AAH is no longer regarded to be a premalignant lesion but rather a benign small glandular process of the transition zone which does mimic acinar adenocarcinoma. In view of the fact that AAH occurs predominantly within the transition zone of prostate gland, which is only rarely sampled in needle biopsy of prostate gland, it has tended to be uncommon to visualise examples of this lesion in biopsy specimens. Nevertheless, as the sampling of the transition zone of the prostate gland had become more frequently undertaken over the past few decades with ultrasound-guided multiple segmental prostate biopsies, as well as radiology-mage guided- targeted prostate biopsies of suspicious lesion with utilisation of also computed tomography scan / magnetic resonance imaging scan, the practicing surgical pathologists needs to be aware of the histopathology examination features of AAH of the prostate in needle biopsy specimens, in order to avoid misinterpretation of AAH of the prostate, which is a benign lesion, as adenocarcinoma of prostate gland. Furthermore, because some patients manifesting with raised serum prostate specific antigen (PSA) levels and negative peripheral zone biopsy may manifest with transition zone adenocarcinoma of prostate gland, sampling of the transition zone of the prostate by needle biopsy and the identification of AAH are likely to increase. If an atypical adenosis hyperplasia (AAH) or adenosis is misdiagnosed as localised adenocarcinoma of the prostate gland, then the individual found to have AAH could be inadvertently treated as a treatment of curative intent of either radical prostatectomy or radical radiotherapy that would represent unnecessary treatment over-aggressive treatment associated with more significant side effects and complications. Nevertheless, if a correct diagnosis of AAH of the prostate gland is established then the patient would not need any surgical or radiotherapy. A number of cases of AAH of prostate gland also tend to diagnosed specimens of trans-urethral resection of prostate gland specimens and prostatectomy specimens. Diagnosis of AAH of prostate gland tends to be diagnosed based upon the histopathology and immunohistochemistry staining features of specimens of the prostate gland, The pathologist also needs to be aware of which antibody staining agents that need to be used in order to clearly confirm the diagnosis of AAH of prostate gland and this has been detailed out in the ensuing article.