Unusual Metastasis of Medullary Thyroid Carcinoma to the Breast: A Cytological and Histopathological Correlation

Breast metastases are a relatively rare condition and account for approximately 0.5-2% of all breast tumors. Recognition of metastatic tumors in the breast is important because it would prevent unnecessary mutilating surgery and would lead to appropriate treatment of the primary tumor. Breast metastases from medullary thyroid cancer (MTC) are very rare with only 21 reported cases in the literature. Some MTCs mimic primary invasive lobular carcinoma of the breast histopathologically and radiologically, making the distinction between the two diagnostically challenging. We present the case of a 45-year-old female presenting with a lump breast, which was later found out to be metastasis from medullary carcinoma thyroid.