Breast metastasis by medullary thyroid carcinoma detected by FDG positron emission tomography.

ABSTRACT

Medullary thyroid carcinoma (MTC) is an uncommon thyroid cancer comprising 5% to 8% of thyroid neoplasms. In contrast to common thyroid tumors, this tumor originates from the calcitonin-producing C cells. Regional metastases to cervical lymph nodes occur early in the disease, whereas distant metastasis occurs late. Common metastatic sites include the liver, bone, brain, and adrenal medulla. We present a case of MTC metastatic to the breast. We report on this case for the following reasons (1) metastasis to the breast is an extremely rare occurrence and could be easily confused clinically and pathologically with a primary breast neoplasm and (2) this is the first reported case of detection of breast metastasis by an MTC using FDG ((18)F-fluoro-2-deoxy-D-glucose) positron emission tomography with an accompanying histologic description.