Value of testicular biopsy in diagnosing carcinoma in situ testis

Quantitative histological studies on four testicles removed because of carcinoma in situ (CIS) were performed in order to determine the likelihood of diagnosing carcinoma in situ testis by biopsy. The CIS changes were evenly distributed in the testicles except for the parts adjacent to the epididymis, where the lesion was less frequent. In parts of the testicles where more than approximately 10% of the testicular volume contained tubules with CIS all simulated biopsies measuring 3 mm contained the lesion. The same was true for simulated biopsies measuring 1.5 mm when more than approximately 30% of testicular volume consisted of tubules with CIS. If the distribution of carcinoma in situ generally is similar to that found in the four analysed testicles there seems to be a high probability of detecting the disease by one or two testicular biopsies of 3 mm.