Frontal bone metastasis from an occult follicular thyroid carcinoma: Diagnosed by FNAC

Metastatic deposits in skull bones from follicular thyroid carcinoma is rare, and metastatic disease in skull being the presenting symptom without obvious thyroid lesion (occult primary) is even rarer. A 60-year-old female patient presented with a mass in the frontal region of the skull. Fine needle aspiration cytology was done which revealed an adenocarcinoma with repeated follicular pattern, reminiscent of follicular neoplasm of thyroid, which on immunocytochemistry revealed positivity for thyroglobulin. Patient was investigated further for primary thyroid malignancy, and imaging revealed a nodule in the left lobe of thyroid. Neuroimaging showed osteolytic lesion involving the cranium.