(0746) Thyroid Carcinoma With Direct Atrial Extension: A Rare Case Report and Review of the Literature

Introduction: Poorly differentiated thyroid carcinoma (PDTC), a rare and aggressive entity, is typically treated with surgery and adjuvant therapy. In the U.S., only two cases of direct intravascular extension of a thyroid malignancy into the right atrium have been reported, neither featuring PDTC.

Methods: We present a unique case and a worldwide literature review, identifying 17 cases of thyroid malignancy featuring direct cardiac extension dating back to 1879.

Results: Our patient presented with a 6.8 cm right thyroid lobe mass and a filling defect of the right internal jugular vein (IJV) and superior vena cava (SVC) on imaging. Intraoperatively, the tumor was found to directly extend into the right atrium via IJV and SVC invasion. En bloc removal of the tumor required total thyroidectomy, neck dissection with IJV sacrifice, sternotomy, SVC veinotomy, and direct right atriotomy. Pathology demonstrated a pT4aN0 PDTC arising from a follicular variant of papillary carcinoma. Adjuvant external beam radiation was implemented with consideration of subsequent radioactive iodine treatment.
Of the 17 reported cases of thyroid carcinoma with direct cardiac extension, the most common histology identified (6 cases) was follicular thyroid carcinoma. Twelve of these patients received treatment, 10 of whom underwent surgery. Among the patients treated with surgery, 9 had defined outcomes, 5 of which were alive at 6 months post-surgery (OR=5). Four of these patients received adjuvant radioactive iodine (RAI) therapy, and one received external beam radiation therapy (XRT).

Conclusions: Our case highlights the challenges in diagnosing thyroid cancer with direct cardiac extension while emphasizing that follicular thyroid carcinoma and follicular variants of thyroid cancer increase the risk of such presentation. We encourage the availability of cardiothoracic surgery to assist with planned extirpative treatment. Finally, our literature review suggests that those undergoing surgery are more likely to be alive at 6 months. External beam radiation and RAI should be considered as adjuvant therapy in such cases.