Papillary thyroid carcinoma (PTC) accounts for the vast majority of thyroid cancer cases. Cerebellar metastasis is rarely the presenting feature. We report a patient presenting with a cerebellar lesion which demonstrated metastatic PTC upon resection, with unusual features including incidental medullary thyroid microcarcinoma without PTC in the main thyroidectomy specimen.

Key Clinical Message: In patients presenting with hyperinsulinaemic hypoglycaemia with a non-pancreatic neuroendocrine tumour, the diagnosis of an ectopic insulin-secreting tumour should be considered, and investigated further with confirmatory insulin staining.