The focus of "atypical glands, suspicious for malignancy" in prostatic needle biopsy specimens: incidence, histologic features, and clinical follow-up of cases diagnosed in a community practice.

This study was undertaken to determine retrospectively the prevalence and histologic features of the atypical foci that are suspicious for but are not diagnostic of a malignancy in contemporary prostate needle biopsy specimens reported in a community practice. Histologic features were examined in detail to identify features that prevented an unequivocal diagnosis of carcinoma. Of 1,009 prostate needle biopsy specimens obtained between January 1, 1993, and August 1, 1995, the diagnosis of an atypical focus suspicious for malignancy was made in 48 (4.8%). In review of the biopsy specimens diagnosed as benign, an additional 7 cases (0.7%) were identified. The following histologic features were identified in 54 cases: enlarged nucleoli, 54 (100%); enlarged nuclei, 45 (83%); intraluminal eosinophilic secretions, 40 (74%); infiltrative growth, 37 (68%); small acinar proliferation, 37 (68%); intraluminal basophilic mucin, 23 (42%); amphophilic cytoplasm, 18 (33%); high-grade prostatic intraepithelial neoplasia, 17 (31%); and crystalloids, 12 (22%). Corpora amylacea were not identified. The foci contained from 1 to 67 acini (mean, 20.7). Although each atypical focus showed most of the features of adenocarcinoma, an unequivocal diagnosis of malignancy was not given owing to four features: the small size of the focus, the small number of cells with enlarged nucleoli, the clustered growth pattern, and the presence of high-grade prostatic intraepithelial neoplasia within many of the foci. At initial examination, 36 of 41 patients (83%) had an elevated serum concentration of prostate-specific antigen (mean, 10 ng/mL), and 20 (49%) had abnormal findings on a digital rectal examination. Twenty-five patients (46%) underwent additional sampling of the prostate, and 15 of these (60%) were found to have adenocarcinoma; the remaining 30 patients did not undergo a subsequent biopsy. Patients with subsequent cancer had higher mean serum concentrations of prostate-specific antigen and change in concentrations of prostate-specific antigen than those whose repeat biopsy results were negative; no other clinical or histologic differences were observed between these two groups. To the community pathologists in this study, the lack of prominent nucleoli, the small size of the focus, clustered acini, and/or adjacent high-grade prostatic intraepithelial neoplasia prevented an unequivocal diagnosis of malignancy. If a prostate needle biopsy specimen is reported as containing an atypical focus suspicious for malignancy, a subsequent biopsy is warranted given the high predictive value for adenocarcinoma.