Thyroid hemiagenesis associated with medullary or papillary carcinoma: report of cases.

BACKGROUND Thyroid hemiagenesis is a rare congenital anomaly in which 1 thyroid lobe fails to develop. Co-occurrence of hemiagenesis and thyroid carcinoma is extremely rare. Here, we report 2 cases of thyroid hemiagenesis with carcinoma. METHODS The first patient was referred with a left thyroid mass and absent right lobe. The frozen section examination revealed medullary thyroid carcinoma (MTC); therefore, a left thyroid lobectomy plus neck dissection was performed. Another patient was referred with a right thyroid mass and absent left lobe. Fine-needle aspiration biopsy was suspicious for papillary carcinoma. The patient underwent right thyroid lobectomy plus neck dissection. RESULTS The operative findings confirmed hemiagenesis of the right lobe and MTC in the left lobe for the first case, and hemiagenesis of the left lobe and papillary carcinoma in the right lobe for the second case. CONCLUSION Our case represents the first reported case of association between thyroid hemiagenesis and MTC.