Elevation of hCG in CSF in pinealoblastoma: a pitfall rescued by pathological examination

Human chorionic gonadotropin (hCG) is a hormone that may be abnormally secreted in several tumour types, including intracranial germ cell tumours. In pineal region tumors, hCG is a key tumor marker. In fact, mild elevation typically suggests a germinoma with syncytiotrophoblastic cells, whereas a markedly elevated level indicates a choriocarcinoma or a mixed germ cell tumor with trophoblastic differentiation. While histopathological confirmation remains the diagnostic gold standard, the anatomical situation of the pineal gland makes biopsy very challenging. In certain situations, diagnosis may therefore rely on a constellation of clinical, radiological, and biochemical findings, including cerebrospinal fluid (CSF) β-hCG levels. However, the differential diagnosis of pineal region tumours includes other primary neoplasms of the pineal parenchyma, which differ markedly in both prognosis and therapeutic management. Here, we report two cases of pineoblastoma with unexpectedly elevated CSF β-hCG levels, which might have led to a misdiagnosis of intracranial germinoma. These cases highlight the need for the development of novel, non-invasive biomarkers to improve the diagnostic accuracy of intracranial tumours.