ITGCN or carcinoma in situ of the testis or testicular intraepithelial neoplasia (TIN): This is a noninvasive premalignant precursor of germ cell tumours. It is commonly found in patients with pre-existing ipsilateral testicular GCT (80 % of patients), but may even be encountered in the contralateral “normal” one (5–10 %) [15]. ITGCN has also been found in association with cryptorchidism, atrophic testis, infertility and hermaphroditism. The progression risk into invasive GCTs increases with time and has been evaluated to be 50 % within 5 years and 70 % within 7 years [16–18].

Past history of a testicular cancer: This exposes the patient to an increased risk of developing a synchronous or metachronous GCT in the contralateral testis. This risk is reported to be higher in patients who are younger at the time of the diagnosis and in those with seminoma [19, 20].

Family history of testicular tumour: Having a first-degree relative with testicular cancer increases the risk of developing this tumour. The median age at diagnosis in such patients with a positive family history is 2–3 years younger than in the general population [21]. Family-linked testicular cancers have been extensively studied by Scandinavian authors who found the individual’s risks for testicular cancer increased by 8- and 4-folds with an affected brother and father [22–24]. A recessive mode of inheritance was proposed as an explanation for the higher correlation between brothers than between a father and his son [25]. The combination of shared childhood environment and heritable causes were suggested as an explanation of this high familial risk. There are few genetic changes described in association with testicular cancer. The most commonly encountered is an isochromosome of the short arm of chromosome 12–i(12p) which was reported in almost all histological types of germ cell tumours [26, 27]. However, a study has shown that the overrepresentation of 12p is more related to invasive growth and is not an early event in the development of testicular GCTs [28]. Alterations in the p53 locus have been described in 66 % of cases of ITGCN.

Other possible risk factors: These include Klinefelter’s syndrome, HIV infection [29], testicular atrophy, infertility, testicular feminization, trauma and hormones. Testicular regression syndrome or vanishing testis syndrome is believed to carry a potential for malignant degeneration in the long term, and it is a common practice to remove such remnants as a preventive measure. However, a recent literature review failed to identify any report of a GCT arising from this condition [30]. This phenomenon should not be confused with the so-called burnt–out germ cell tumour, a yet unexplained regression of the primary testicular lesion in metastatic germ cell tumour which could be due to immunological reactions.