Brain metastasis mimicking a cavernous angioma as initial presentation of papillary thyroid carcinoma.

Summary: Brain metastases as the first clinical presentation of a papillary thyroid carcinoma (PTC) are exceptional, while cavernous angiomas are common cerebral malformations. We report the case of a 36-year-old male with an incidental brain lesion mimicking a cavernous angioma on MRI. Gamma knife radiosurgery was performed, but after 6 months, the patient developed neurological symptoms, and a repeat brain MRI revealed a significant increase in the mass. The patient underwent neurosurgery, and the histological examination of the lesion revealed metastatic carcinoma of thyroid origin. PET-CT and neck ultrasound, subsequently performed, were concordant for the presence of a right lobe nodule and ipsilateral lymph nodes, both with ultrasound features suspicious of malignancy. Total thyroidectomy with central and right lateral neck dissection was performed, and histology confirmed an intrathyroidal multifocal PTC with lymph node metastases. Postoperative radioiodine was administered, and focal uptake within the thyroid bed, without distant metastases or brain remnants, was found on the post-therapeutic whole-body scan. At 2 years from diagnosis, the patient is in good health and undergoes clinical and imaging follow-up. Learning points: Brain cavernous angiomas are common cerebral vascular malformations that are usually diagnosed by MRI. Despite the high accuracy of MRI, the exam is not pathognomonic, and misdiagnosis cannot be excluded. Brain metastases from PTC are very rare; however, they can mimic a cavernous angioma. Therefore, the differential diagnosis should always be considered.