Diagnostic criteria of limited adenocarcinoma of the prostate on needle biopsy.

Over a period of 25 weeks 434 needle biopsy specimens of the prostate were sent to the author for consultation because of diagnostic concerns. The final diagnoses were cancer (69%), benign (13%), atypical but not diagnostic (10%), high grade prostatic intraepithelial neoplasia (PIN) (5%), and miscellaneous (3%). The most common benign entities mimicking cancer were atrophy (29 specimens) and adenosis (19 specimens). The 300 cancer specimens were analyzed further. Architecturally, the presence of small glands between larger benign glands was the most common pattern seen in 80% of carcinomas; haphazard growth patterns, single cells, and cribriform glands were seen less frequently. The following diagnostic features were helpful: nuclear enlargement (77% of specimens); prominent nucleoli (76%); pink acellular intraluminal secretions (53%); amphophilic cytoplasm (39%); blue-tinged mucinous secretions (34%); crystalloids (25%); PIN (13%); mitotic figures (11%); and perineural invasion (3%). The mean and median numbers of malignant glands in this series were 31 and 20, respectively (range, two to 300). Tumors with a Gleason score lower than 6 caused greater diagnostic problems for referring physicians because these tumors had a greater number of malignant glands, yet were still sent in for consultation (P = .0018). Gleason score was positively correlated with prominent nucleoli and amphophilic cytoplasm and inversely correlated with the presence of crystalloids. Prominent nucleoli, which often are quoted as being essential for the diagnosis of prostate cancer, were not seen in 24% of the specimens and seen only rarely in another 25%. The diagnosis of prostate cancer is based on a constellation of features. Even in this series with a limited number of malignant glands, 85% of specimens contained three or more of the above-listed diagnostic features in addition to architectural atypia.