Objectives. To validate with an independent study that simple atrophy/postatrophic hyperplastic lesions (proliferative inflammatory atrophy [PIA]) often merge directly with high-grade prostatic intraepithelial neoplasia (PIN).

Methods. Using radical prostatectomies (n =14), all high-grade PIN and adenocarcinoma lesions were identified. We examined the two-dimensional topographic relationship between individual high-grade PIN lesions and PIA, between carcinoma lesions and PIA, and between carcinoma lesions and high-grade PIN. To reduce the possibility that high-grade PIN lesions represented intraprostatic dissemination of carcinoma, all specimens contained total carcinoma volumes of less than 0.5 cc.

Results. High-grade PIN merged with PIA in 267 (42.5% of high-grade PIN lesions) of 629 lesions, was adjacent in 57 lesions (9%), was near in 233 lesions (37%), and was distant from PIA in 72 lesions (11.5%). Carcinoma did not merge with PIA; it was adjacent in 24 (30.4%) of 79 lesions, was near in 46 lesions (58.2%), and was distant from PIA in 9 lesions (11.4%). Of 79 carcinoma lesions, 18 (23%) merged with high-grade PIN, 11 (14%) were adjacent, 26 (33%) were near, and 24 (30%) were distant from high-grade PIN. Areas of presumed low-grade PIN were often found in association with high-grade PIN and PIA.

Conclusions. Morphologic transitions between high-grade PIN and PIA occur frequently. Although the mere topographic relation of the lesions is not definitive proof of a continuum, these results are consistent with a model in which the proliferative epithelium in PIA may progress to PIN and/or adenocarcinoma.