Metastatic papillary thyroid cancer to cerebellum with incidental medullary microcarcinoma

Thyroid cancer is the most common endocrine cancer, with papillary thyroid carcinoma (PTC) accounting for the majority of these cases. Cerebellar metastasis is rarely the presenting feature and confers poor prognosis. Genetic mutations in this setting are most commonly TERTp, in contrast to BRAF in the majority of PTC. We report the case of an 82 year-old male who presented with a symptomatic right cerebellar lesion and underwent surgical resection to demonstrate metastatic PTC. Extensive workup with computed tomography, neck ultrasound and FDG-PET was suggestive of a left thyroid primary lesion, with FNA confirming PTC. However, total thyroidectomy demonstrated incidental microMTC (medullary thyroid microcarcinoma, defined as tumour <10mm) without any evidence of PTC, whereas the left level VI neck dissection demonstrated a 30mm nodule of PTC without identifiable normal thyroid or lymph node tissue.