Needle biopsies of the prostate: what constitutes adequate histologic sampling?

Abstract

Objective: The automated biopsy gun and increased screening for adenocarcinoma of the prostate have led to increased numbers of biopsies with only tiny foci of prostatic carcinoma. Consequently, the risk of failing to sample a small focus of carcinoma histologically has increased as well. Most pathologists routinely sample prostatic needle biopsies at more than 1 level. An expert panel has recently suggested that prostatic needle biopsies be sampled at at least 2 levels. However, there have been no studies measuring the amount of additional tissue sampled by multiple levels versus 1 level.

Methods: Forty-two prostatic needle biopsies were serially sectioned at 4-microm levels. Hematoxylin-eosin-stained slides were prepared from every fifth section. The total length of each biopsy was compared with the length sampled by 1 level (50% through the block) and 3 levels (25%, 50%, and 75% through the block).

Results: Sampling the tissue at 1 level missed an average of 23.4% of the total biopsy length. Sampling the tissue at 3 levels significantly improved this average to 7% (P = .0001).

Conclusions: This study shows that a single histologic section of a prostatic needle biopsy often fails to sample a significant portion of available tissue. This could occasionally result in failure to sample a small focus of prostatic carcinoma. The authors recommend that prostatic needle biopsies be routinely sampled at 3 levels (approximately 25%, 50%, and 75% through the block).