Evolving patterns of tissue composition in benign prostatic hyperplasia as a function of specimen size.

The tissue composition in 36 transurethral resections and four prostate enucleations for benign prostatic hyperplasia (BPH) was quantitated by computerized morphometric techniques using 15 morphologic categories. Data were compared between seven consecutive weight ranges. Nodules of glandular and/or stromal tissue comprised only 5% of tissue in the smallest resections, while bladder neck and anterior fibromuscular tissue represented more than half the specimen. Non-nodular prostatic tissue from the transition zone was the dominant resected component in all but the largest specimens (enucleations) where nodules comprised most of the tissue. Though nodules comprised only 22% of the largest transurethral resections, their contribution to hyperplasia increased more rapidly than any other component. Glandular nodules with a high ratio of epithelium to stroma dominated at all weight ranges. It was concluded that tissue resected for BPH is quite heterogeneous, that nodules comprise most of the tissue only in specimens over 50 g in weight, and that the most common hyperplastic component is histologically normal tissue. Benign prostatic hyperplasia undergoes morphologic evolution with increasing weight, and epithelial-rich nodules are the most rapidly evolving component.