Argon-helium cryoablation treatment of undifferentiated pleomorphic sarcoma of the thyroid: A case report and literature review.

Undifferentiated pleomorphic sarcoma is an extremely rare malignant thyroid tumor. Thyroid sarcoma differs from common malignant thyroid tumors, such as thyroid follicular cell carcinoma. It is usually highly malignant, progresses rapidly, and is prone to remote metastasis.