A rare case of medullary carcinoma thyroid metastasizing to bilateral breast parenchyma

Medullary carcinoma of the thyroid (MTC) commonly spreads through the lymphatics to distant sites such as lung, liver and bone. Spread to the breast is rare. We report a case of metastatic MTC which progressed to develop nodal metastases to cer­vical and mediastinal regions, visceral metastases to the liver, lung and ultimately to bilateral breasts. Clinically it is important to distinguish metastatic breast lesions from primary breast cancer as each is managed differently. Both cytological and radio­logical investigations were done followed by excision biopsy. Histopathological examination of post excision breast specimen revealed metastatic medullary carcinoma, with positive immunohistochemical staining for calcitonin. A brief review of literature and differential diagnosis is also presented.