Low grade adenocarcinoma simulating benign glandular lesions in needle prostatic biopsy

In order to define the frequency and morphological characteristics of low grade adenocarcinomas misdiagnosed as benign prostatic hyperplasia in needle prostatic biopsies, we reviewed 135 consecutive needle biopsies with prostatic cancer. In three biopsies (2.2%) low grade adenocarcinoma was found as a single neoplastic pattern simulating benign hyperplastic gland in some histological fields and prostatic adenosis in others. These biopsies showed the histological features described for carcinomas originating in the transition zone and were seen in isolated histological fields. Retrospectively, it was found that these biopsies showed features of adenocarcinoma although some histologic criteria of malignancy such as infiltrative pattern, prominent nucleoli and nuclear enlargement were seen only focally. Blue mucinous secretions, crystalloids, occasional stromal single cells and mitotic figures were absent. We conclude that a detailed analysis of architectural and cytological features must be made of all glandular proliferations, since this type of low grade adenocarcinoma can occasionally be found in needle prostatic biopsies as the only neoplastic pattern in needle biopsy specimens and simulate benign glandular lesions.