Mucin expression in atypical adenomatous hyperplasia of the prostate.

Prostatic atypical adenomatous hyperplasia (AAH) is a small glandular proliferation that has histological similarities with well-differentiated adenocarcinoma. To determine the histochemical profile of AAH, we assessed the production of total neutral mucin, total acidic mucin, and sulfated acidic mucin in 24 cases of AAH, five cases of Gleason primary pattern 1 and 2 adenocarcinoma, and 29 cases of adjacent benign and hyperplastic prostatic tissue. All specimens were formalin-fixed transurethral resections, and the diagnosis in each was confirmed by evaluation of the keratin 34B-E12 immunoreactive basal cell layer (intact in benign and hyperplastic epithelium, fragmented in AAH, and absent in cancer). The extent of mucin staining was measured semiquantitatively in 10% increments according to the number of stained glands. Neutral mucin was found in all but two cases, and there was no apparent difference in the amount of staining in benign glands, AAH, and cancer (mean number of stained glands, 43%). Total acidic mucin was more common in AAH (63% of cases; mean, 11% of glands) and adenocarcinoma (60% of cases; mean, 30% of glands) than in benign glands (0% of cases). Similarly, nonsulfated acidic mucin was more common in AAH (63% of cases; mean, 12% glands) and adenocarcinoma (60% of cases; mean, 8% of glands) than in benign glands (0% of cases); the pattern and intensity of staining for nonsulfated acidic mucin appeared to be similar to that for total acidic mucin in AAH and cancer. These findings indicate that there is a close relationship in mucin expression between AAH and well-differentiated adenocarcinoma. Identification of acidic mucin should be used cautiously as an adjunct in the diagnosis of adenocarcinoma but is useful in separating some cases of AAH and adenocarcinoma from benign prostatic epithelium.