ABSTRACT: BACKGROUND: Testicular Germ Cell Tumours (TGCT) are the most frequently occurring malignancy in males from 15--45 years of age. They are derived from germ cells unable to undergo physiological maturation, although the genetic basis for this is poorly understood.A recent report showed that mutations in the RNase IIIb domain of DICER1, a micro-RNA (miRNA) processing enzyme, are common in non-epithelial ovarian cancers. DICER1 mutations were found in 60 of Sertoli-Leydig cell tumours, clustering in four codons encoding metal-binding sites. Additional analysis of 14 TGCT DNA samples identified one case that also contained a mutation at one of these sites. FINDINGS: A number of previous studies have shown that DICER1 mutations are found in Q) within the RNase IIIb domain in one TGCT sample, which was predicted to disturb DICER1 function. CONCLUSION: Overall our findings suggest a mutation frequency in TGCTs of 1 . We conclude therefore that hot-spot mutations, frequently seen in Sertoli-Leydig cell tumours, are not common in TGCTs.