Prostate cancer screening and early detection efforts have resulted in the identification of smaller volume carcinomas of the prostate. We evaluated the diagnostic features of minimal (< 1 mm) carcinoma in sextant needle biopsy specimens of the prostate and in follow-up analyzed the features of the corresponding carcinomas in the whole gland. We reviewed specimens from 50 consecutive patients who had minimal carcinoma in needle biopsy tissue and who had undergone radical prostatectomy. Histologic grade, tumor size, pathologic stage, and margin status of the 50 carcinomas in the whole gland in which the carcinoma size was minimal in the sextant needle biopsy specimen were compared with those of 50 carcinomas in the whole gland in which carcinoma size was greater than 1 mm in the needle biopsy specimen. The most common morphologic features of these minimal carcinomas were nucleomegaly (96%), infiltrative growth pattern (88%), intraluminal secretions (78%), prominent nucleoli (64%), associated high-grade prostatic intraepithelial neoplasia (40%), amphophilic cytoplasm (36%), hyperchromatic nuclei (30%), and intraluminal crystalloids (22%). Perineural invasion (2%), collagenous micronodules (2%) and mitotic figures (2%) were uncommon. The mean tumor volume in the whole gland of carcinomas corresponding to minimal carcinoma in a needle biopsy specimen was significantly smaller (P=.029) at 1.1 mL than it was in carcinomas with tumor greater than 1 mm in the needle biopsy specimen at 1.6 mL, but other pathologic features of carcinoma in the whole gland were not significantly different. In conclusion, a constellation of morphologic attributes is important for establishment of a diagnosis of minimal carcinoma of the prostate in needle biopsy specimen. Most (82%) of the corresponding prostate cancers in the whole gland were pathologically significant.