Atypical adenomatous hyperplasia of prostate lacks TMPRSS2-ERG gene fusion.

Atypical adenomatous hyperplasia (AAH) is a distinct entity in prostate pathology, defined as a well-circumscribed lobule of closely packed crowded small glands or acini. Although it has been proposed as a precursor lesion to prostate cancer, the biological nature of AAH is currently uncertain. The TMPRSS2-ERG fusion gene is a common recurrent chromosomal rearrangement in prostate cancer and in its precursor lesion, prostatic intraepithelial neoplasia. The prevalence of TMPRSS2-ERG alteration in AAH is unknown. Fifty-five separate prostate specimens containing AAH were investigated by fluorescence in situ hybridization and immunohistochemistry for TMPRSS2-ERG rearrangement. TMPRSS2-ERG rearrangements were not identified in AAH either by fluorescence in situ hybridization or by immunohistochemistry.