Metastatic carcinoma to the thyroid gland: a single institution 20-year experience and review of the literature.

The thyroid gland is an uncommon site for metastatic disease but cases have been well-documented in the literature, particularly in autopsy series. A retrospective review of surgical pathology and autopsy pathology database for patients with metastatic carcinoma to the thyroid was performed at the University of Massachusetts Medical Center between January 1993 to January 2013. We identified a total of 10 patients with metastatic carcinoma to the thyroid; 6 were in surgical pathology specimens out of a total of 1,295 thyroid carcinoma (0.46 %) and 4 were diagnosed at autopsy out of a total of 2,117 (0.19 %) autopsy cases during this period. Cases with direct extension of the tumor into the thyroid from local primary sites such as larynx, esophagus or soft tissues of the neck were excluded. The primary tumors in these cases comprised of four lung carcinomas, three colorectal carcinomas, a renal cell carcinoma, a pleural malignant mesothelioma, and an unknown primary. Therefore, it is important to keep intrathyroidal metastases in the differential diagnosis when evaluating a thyroid nodule, particularly in patients with a previous history of malignancy. Furthermore, a literature review reveals over 1,400 cases have been previously reported, with the most common malignancies from the kidney (34 %), lung (15 %), gastrointestinal tract (14 %), and breast (14 %).