Intracranial germ cell tumours (ICGCT) are rare tumours that primarily affect children and adolescents, with a male predominance, accounting for 3.6% of brain tumours in Western Europe and reaching a higher incidence of 15.4% in Japan
[1][2][3][1,2,3]. A comparative study between Japanese and American populations regarding ICGCT revealed a different distribution of the tumours. More cases of basal ganglia involvement were present in the Japanese, whereas more bifocal (synchronous pineal and suprasellar) locations in western society, suggesting the presence of genetic or environmental factors, thus, contributing to the phenotypic diversity
[4]. According to the WHO classification of the central nervous system (CNS) tumours, the germ cell tumours group, composed of germinoma, represents the most common histological type (60%), followed by mixed germ cell tumours (17.4%), teratoma (15.7%), yolk sac tumour (4.2%), choriocarcinoma (1.6%), and embryonal carcinoma (1.1%)
[5]. According to Matsutani et al., pure germinoma and mature teratoma have a good prognosis, but other histological types may result in unfavourable prognosis. Intermediate prognosis corresponds to germinoma with syncytiotrophoblastic giant cell [STGC], immature teratoma, teratoma with malignant transformation and mixed tumours composed mainly of germinoma or teratoma, whereas poor prognosis is found in choriocarcinoma, yolk sac tumour, embryonal carcinoma, as well as in mixed tumours composed mainly of choriocarcinoma, yolk sac tumour, or embryonal carcinoma
[6][7][6,7].
Germinomas usually develop in the midline areas of the brain, most often in the pineal gland (50% of the pineal tumours are germinomas) and the suprasellar region
[8]. In approximately 5–10% of the cases, the tumour is ectopically situated (in other areas than neurohypophysial or pineal sites), including the basal ganglia, thalamus, corpus callosum, cerebellum, septum pellucidum, temporal lobe, and the spinal cord
[9][10][11][12][13][9,10,11,12,13]. Suprasellar germinomas are associated with female patients (<15 years old), while pineal germinomas with male patients (>15 years)
[14]. In rare cases, germinomas have been described to occur later in life. Several reports mention the diagnosis in the sixth or seventh decade of life, outlining the fact that germinoma should be included as a differential diagnosis even in the elderly
[15][16][17][18][19][15,16,17,18,19]. Germinomas can also be present as synchronous lesions in the pineal region and hypothalamo-neurohypophyseal axis, also referred to as “bifocal germinomas”, with an incidence ranging from to 6% to 26% and even as high as 41% in some studies
[20][21][22][23][24][20,21,22,23,24]. Metastatic germinomas caused by the dissemination of tumour cells through the cerebrospinal fluid are reported in approximately 4.5% of the cases, usually after a mean period of 6–7 years after the initial tumour diagnosis
[25][26][25,26]. According to the literature, the most common type of metastasis is spinal “drop metastasis” (32.5%), followed by ventricular dissemination (30%), and to a lesser extent, the suprasellar region, corpus callosum, subarachnoid space
[26][27][28][26,27,28]. Concomitant metastases to the ventriculoperitoneal shunt can appear in 20% of the cases
[26].