ABSTRACT
OBJECTIVE: Primary central nervous system germ cell tumors are rare neoplasms usually located in the pineal and/or suprasellar region. Pure germinomas do not usually secrete beta-human chorionic gonadotropin hormone (beta-HCG) or alpha-fetoprotein (AFP) and diagnosis is made a few weeks or months after beginning of symptoms. CASE: Here we report a case of a pure germinoma in a 20 year-old woman presenting as a sellar mass with suprasellar extension, abnormal serum beta-HCG and a long history of polyuria and polydipsia (4 years), that was initially diagnosed as a pituitary macroadenoma. CONCLUSION: This presentation highlights the importance of thinking in alternative diagnosis to pituitary adenoma when diabetes insipidus is the initial symptom.