PROSTATIC ADENOCARCINOMA WITH ATROPHIC FEATURES - MALIGNANCY MIMICKING A BENIGN PROCESS

Acinar atrophy and postatrophic hyperplasia in the prostate are common ly confused with adenocarcinoma. The converse situation may also prese nt a diagnostic dilemma. We recently encountered a number of cases of adenocarcinoma with features that mimicked atrophy, raising the seriou s concern for the un derdiagnosis of malignancy. To investigate the fr equency of prostatic adenocarcinoma with atrophic features and the his tologic criteria that allow its distinction from benign processes, we reviewed the histopathologic findings in 202 consecutive totally embed ded whole-mount radical prostatectomy specimens with adenocarcinoma, 1 00 consecutive routine needle biopsy specimens, and five additional se lected needle biopsy specimens. None of the patients had received andr ogen deprivation therapy before specimen acquisition. Prostatic adenoc arcinoma with atrophic features was defined as a proliferation of mali gnant acini that architecturally resembled atrophy or postatrophic hyp erplasia but retained the diagnostic cytologic features of cancer. The acini were round, often dilated and distorted, and lined by flattened attenuated epithelium with scant cytoplasm. All cases had cytologic e vidence of malignancy, including nuclear enlargement and prominent nuc leoli; these findings could not be attributed to inflammation or treat ment effect. Atrophic features were identified in cancer in six radica l prostatectomy specimens (3%) and two routine needle biopsy specimens (2%). The proportion of cancer with atrophic features comprised a mea n of 27% of each tumor in the prostatectomy specimens (range 10-60%) a nd 24% in the needle biopsies (range 10-90%). In the prostatectomy cas es, the Gleason score of the cancers was 7 (in five cases) and 5 (in o ne case); in the biopsy specimens the Gleason score was 6 (in five cas es) and 7 (in two cases). In addition, atrophic cancer in the prostate ctomy cases had luminal eosinophilic proteinaceous secretions (six cas es), blue mucin (five cases), crystalloids (two cases), apocrine blebs (three cases), collagenous micronodules (one case), and high-grade pr ostatic intraepithelial neoplasia within two high-power fields (three cases); the histologic features were similar in the needle biopsy spec imens. We conclude that prostatic adenocarcinoma with atrophic feature s is an unusual finding that is easily confused with benign acinar atr ophy. It is recognized by a combination of architectural and cytologic findings and usually coexists with typical Gleason score 5-7 acinar a denocarcinoma. This pattern is important to recognize to avoid the und erdiagnosis of malignancy.