Intracranial germ cell tumours presenting with AVP deficiency and evolving panhypopituitarism: diagnostic pitfalls in...

We report three Chinese children with central nervous system germ cell tumours (CNS GCTs) presenting as arginine vasopressin (AVP) deficiency with or without pituitary stalk thickening, initially diagnosed as lymphocytic hypophysitis (LyH) and idiopathic AVP deficiency. Case 1 showed conflicting biopsy results, suggesting hypophysitis and then germinoma. Case 2 had one negative transsphenoidal biopsy and later one biopsy finding LyH before suprasellar mass diagnosis. Case 3 had a normal initial MRI brain and was followed up as idiopathic AVP deficiency but found to have extensive tumour the next year. All patients achieved remission with chemotherapy and radiotherapy but sustained lifelong panhypopituitarism. Asia has a higher prevalence of CNS GCTs in children. Pituitary stalk thickening with risk factors including pituitary stalk thickness ≥6.5 mm, AVP deficiency, two or more pituitary hormone deficiencies at presentation, and evolving hypopituitarism mandates a high level of malignant suspicion even if prior histopathology is negative. In ethnic groups where the prevalence of CNS GCT is higher, biopsy should be offered when presented with risk factors. These cases highlight pitfalls of false-negative MRI and biopsy, emphasising epidemiology-informed diagnostic algorithms to prevent diagnostic delays.