Dieckmann KP, Classen J, Loy V. Diagnosis and management of testicular intraepithelial neoplasia (Carcinoma in situ) – Surgical aspects. APMIS 2003;111:64–9. Germ cell tumours (CT) are no true carcinomas; therefore the term testicular intraepithelial neoplasia (IN) is probably more appropriate than “CIS”. The diagnostic accuracy of a single-site biopsy is an open question. We experienced 9 false-negative biopsies among 1859 cases. Thus, the proportion of a failed diagnosis is 0.5%. The main reason for diagnostic failure is the non-random distribution of TIN within the testicle. Currently we are investigating whether a two-site biopsy is more accurate than a single biopsy. In the ongoing trial, the over-all prevalence of TIN is around 5.3%, so far. In one quarter of the positive cases the lesion was found in only one of the two specimens. Thus, a double biopsy appears to be more favourable than the traditional single biopsy. Surgical complications amount to 2.5% in that double biopsy study. Only one surgical re-intervention was required among 983 patients. Serial imaging studies with scrotal sonography and magnetic resonance imaging (MRI) disclosed a transient intratesticular haematoma/oedema postoperatively. So, testicular biopsy, even when performed at two sites is in fact a low-complication procedure. Low dose radiotherapy to the testis is the treatment of choice for TIN. However, more than one quarter of patients require testosterone supplementation secondary to androgen-deficiency. Two dose-reduction studies (Denmark and Germany) had to be terminated prematurely because unexpected relapse of TIN was encountered at 14 Gy and 16 Gy. Possibly, hyperfragmentation schedules can overcome the antagonism of androgenic compromise and oncological safety. In a nation-wide survey, it was shown that contralateral biopsies were routinely performed in 66% of the urological departments in Germany. Another 19% offered the biopsy to particular “risk-cases”; only 15% never did a biopsy. Among those refusing biopsies, there was a higher proportion of small hospitals and a significantly lower annual case-number of GCT, when compared to those doing the biopsy. Thus, the contralateral biopsy is a well-established procedure among German urologists; those with a high caseload of GCT particularly appreciate it.