Minimal (Limited) Pseudohyperplastic Prostatic Adenocarcinoma in Needle Prostatic Biopsy.

BACKGROUND: Study of minimum adenocarcinoma has been done almost exclusively on conventional acinar adenocarcinoma. Pseudohyperplastic adenocarcinoma can be confused with benign lesions because of its well-differentiated appearance and has not been studied when the biopsy shows few malignant glands (limited carcinoma).

METHODS: We reviewed 94 pseudohyperplastic adenocarcinomas diagnosed in prostatic biopsies for a period of 12 years and selected those measuring less than 1 mm or involving less than 5% of the biopsied tissue. We also reviewed 200 consecutive consultations.

RESULTS: Four (4.2%) of the 94 cases were limited pseudohyperplastic adenocarcinomas, and 3 were from consultations. Three of them were mistaken for hyperplastic nodules, prostatic adenosis, or prostatic intraepithelial neoplasm. The number of glands varied between 6 and 50 (average 23). Three nodular histological patterns were identified-nodular, adenosis-like, and pseudohyperplastic carcinoma resembling prostatic intraepithelial neoplasia. The diagnosis of adenocarcinoma was not related to the number of neoplastic glands. Histological criteria that were useful included: crowded medium to large glands, papillary infoldings, branching glands, straight luminal borders, hyperchromatic nuclei, nucleomegaly, and apparent nucleoli. Areas of transition to conventional acinar adenocarcinoma were useful in recognizing four of these neoplasms, but were barely apparent in 2 of them. Hyperchromatic nuclei were found in all cases, whereas apparent nucleoli and nucleomegaly were only present in 4.

CONCLUSIONS: The architectural and cytological criteria for limited acinar adenocarcinoma are only partially useful in interpreting minimum pseudohyperplastic adenocarcinomas. Knowledge of the criteria for malignancy in both neoplasms is important in order to avoid underdiagnosis of malignancy.