Intracardiac metastasis of follicular thyroid carcinoma.

Thyroid tumors represent approximately 1% of neoplasms diagnosed in Brazil, according to data from the National Cancer Institute. Most cases are differentiated carcinomas, with only 5% to 10% producing distant metastases. Follicular carcinoma, the second most common subtype, is known for its angioinvasive characteristics, typically observed microscopically and locally. Extension to large vessels and the heart is exceedingly rare, with only a few cases reported in the literature. This aggressive form of the disease often presents with exuberant symptoms, primarily superior vena cava syndrome and right ventricular outflow tract obstruction. The hematogenous spread characteristic of follicular carcinoma increases the likelihood of distant metastases, though cardiac involvement remains uncommon. Recent studies have suggested that aggressive surgical intervention, when feasible, can significantly improve outcomes in these rare cases. This report illustrates a female patient with asymptomatic intracardiac follicular thyroid carcinoma who underwent successful surgical resection.