We present an unusual case of calcitonin-negative MTC arising in a “burnt out” thyroid where the only remaining significant cellular elements included putative UBB remnants, C-cell hyperplasia/medullary microcarcinomas (CCH/MMC), and MTCs, which were all MTC classifier positive according to ThyroSeq®. This evidence concerns the gene CALCA and columnar cell hyperplasia of the breast.