The prostate needle biopsy gun: busting a myth

Abstract

Purpose: It is widely reported that a prostate biopsy gun needle advances 0.5 cm and then obtains the subsequent 1.5 cm of tissue. Based on this presumed skip area it is recommended that the needle tip must be placed 0.5 cm from the capsule before firing to obtain the capsule with the specimen. Contrary to this longstanding recommendation, in our experience we have observed that there is no such skip area. We determined the actual content of a needle core by obtaining biopsies from an apple model with clinical correlation to validate our findings.

Material and methods: Using 3 types of spring-loaded biopsy needles we obtained 24 cores from an apple. We placed the biopsy needle tip directly adjacent to the capsule before firing the biopsy gun. Visual inspection of each biopsy core was done to confirm the presence or absence of the capsule (red apple peel).

Results: All cores had confirmed presence of the apple peel, confirming the absence of a skip area in the first 0.5 cm.

Conclusions: Using spring-loaded biopsy guns we observed in an apple model that the capsule is obtained when the biopsy needle tip is placed directly adjacent to the capsule. Urologists placing the biopsy needle tip directly on the capsule in line with the projected trajectory will obtain the prostatic capsule in the specimen and should not withdraw the needle unless the gland depth is short enough so that there is risk of firing past the gland.