BACKGROUND: Pituitary metastasis of thyroid carcinoma is a rare entity. Differential diagnosis with other lesions in the sellar/parasellar region, through clinical, histopathological, immunohistochemical, and imaging is challenging but essential for adequate treatment.

CASE REPORT: This case report describes a 58-year-old patient with the previous diagnosis of follicular thyroid carcinoma, with metastasis to cervical lymph nodes, bone, and lung, initially evolving to left palpebral ptosis. In the investigation, laboratory tests showed hypopituitarism, and magnetic resonance imaging of the skull showed a suprasellar formation measuring 2.2×3.5×2.5 cm, which increased in size in a few months. The patient underwent transcranial neurosurgery and subsequent immunohistochemical analysis, which confirmed pituitary metastasis of follicular thyroid carcinoma. The patient underwent chemotherapy and radiotherapy but died 26 months after the onset of symptoms.

CONCLUSIONS: The differential diagnosis of pituitary metastasis from a benign lesion is difficult. Therefore, a careful analysis of the history and clinical evolution, use of complementary imaging tests, and, where possible, the histopathological and immunohistochemical analysis of the lesion for diagnostic elucidation are necessary.

Keywords: Adenocarcinoma, Follicular, Diabetes Insipidus, Neurogenic, Pituitary Neoplasms, Thyroglobulin