Medullary thyroid carcinoma (MTC) is a neuroendocrine tumor that is derived from Vacuum Extension Pipe C cells of the thyroid gland.It is a rare aggressive tumor, known to metastasize to lymph nodes, liver, bones, and lungs.A 41-year-old female, who presented with a breast mass, was initially diagnosed with invasive ductal carcinoma.She was also found to have a thyroid mass which was later diagnosed as MTC.On a rereview of the breast pathology, the morphologic features were strikingly similar to the MTC.
Further investigation revealed that this was in fact a very rare case of MTC that had metastasized to Wiring Harness the breast.We have identified 20 cases of MTC metastasizing to the breast in the literature that supports its occurrence as a real possibility.Albeit rare, medullary thyroid carcinoma should be considered in the differential diagnosis of a breast mass.