Abstract
An 86th years old woman presented to the emergency room with status post syncope, dysarthria and prostration. Personal history of essential hypertension and a history of hip replacement. Physical examination was unremarkable: Glasgow coma scale 15, without neurologic deficits. An 86th years old woman presented to the emergency room with status post syncope, dysarthria and prostration. Personal history of essential hypertension and a history of hip replacement. Physical examination was unremarkable: Glasgow coma scale 15, without neurologic deficits. Brain CT revealed a frontoparietal mass with bone destruction, but without oedema or mass effect. Within thirty minutes, she started an acute confusional and aggressiveness status. Complete body CT had no alterations. Had repeated brain CT that revealed a massive expansive bilateral parietal lesion, with bone destruction, and mass effect but without oedema. Thyroid ultrasound showed a big gland with heterogeneous nodes and its biopsy revealed a follicular lesion with undetermined meaning, Bethesda III category. Brain biopsy showed a carcinoma metastasis with possible origin in the thyroid gland.
After the behavioural changes and the brain mass associated, the brain metastases are the most likely hypothesis. Searching the primitive tumour, the diagnosis of thyroid carcinoma was achieved.
There are four types of thyroid gland tumours: papillary (80%), follicular (10%); Medullary (5-10%) and anaplastic (1-2%).
In this case, the histology of follicular carcinoma was unexpected since it is a rare type and rarely causes brain metastasis when compared with the medullary one. The clinical manifestation of the metastasis drives us to the primitive tumour diagnosis.

Key words: Thyroid, Brain, Cancer, Metastasis