Update on the diagnostic safety for detection of testicular intraepithelial neoplasia (TIN)

Testicular intraepithelial neoplasia (TIN) of the testis is the noninvasive precursor of testicular germ cell tumours (GCT) and can be detected by a single random biopsy in 5% of patients with GCT in the contralateral testes. Although it is generally presumed that TIN is dispersed throughout the testis, we realize in about 60% of TIN bearing tissue close to testis tumours that its distribution is not homogenously diffuse, but may be focal. Thus we tested whether we can improve diagnostic safety in detecting TIN by increasing the number of biopsies. We could finally evaluate 295 men with proven testicular tumours. Three biopsies of contralateral testes were taken (each 5 mm length) from one surgical incision site and fixed in Bouin's solution or glutaraldehyde. TIN cells were histologically identified by their typical morphological characteristics and additionally by placental alkaline phophatase (PlAP) immunohistochemistry. Patients revealed testicular tumour without contralateral TIN in 271 cases and with contralateral TIN in 24 cases (8.1%). In 6 of these 24 men with contralateral TIN the cells could be detected in only one (n=5) or two (n=1) of the three specimen investigated. That means in these six patients TIN could have been missed if only one single random biopsy was taken. By increasing the number of biopsies (=increasing the number of investigated seminiferous tubules) the detection rate of contralateral TIN may be increased up to 8.1%. Thus we recommend multiple testicular biopsies to increase the diagnostic safety in detection of TIN. Biopsies may be taken from one randomly chosen surgical incision site.