Colorectal cancer metastases to the thyroid gland-a systematic review : Colorectal cancer thyroid metastases.

BACKGROUND Despite its rich vasculature, the thyroid gland is a rare site of metastatic disease. We present a systematic review of colorectal cancer (CRC) thyroid metastases, with emphasis on diagnosis, therapeutic management, and oncological outcomes. METHODS A systematic review of the English literature (1990 to 2019) was performed, using the PubMed, Embase, and Google Scholar bibliographic databases. For each patient, epidemiological, surgical, histopathological, and oncological data were extracted. RESULTS A total of 111 patients (40% males, mean age 61 ± 12 years) were included in the final analysis. The primary CRC was locally advanced (T3-T4) in 83%, had positive lymph nodes (N+) in 65%, and had distant metastases (M+) in 28%. Thyroid metastases were synchronous in 15% and metachronous in 80%, with a mean interval of 51 ± 31 months from primary tumor treatment. Thyroid metastatic disease was diagnosed clinically (60%), radiologically (33%), biochemically (2%), or postmortem (5%). When performed, FNA biopsy was diagnostic in 73% and highly suspicious in 13%. A total of 63% of patients had additional distant metastases, usually in the liver or lungs, while 68% of patients underwent surgical excision (total or subtotal thyroidectomy 58%, lobectomy 42%) and 43% received adjuvant chemotherapy or radiotherapy. Mean overall survival after primary CRC was 55.5 ± 34.7 months, with mean disease-free survival of 31.3 ± 27.2 months. Following diagnosis or treatment of thyroid metastases, 1-, 2- and 3-year survival rates were 79, 66, and 60%, respectively. Mean survival following diagnosis of thyroid metastases was 11.3 months. CONCLUSIONS CRC thyroid metastasis is a relatively uncommon event, usually associated with locoregionally advanced tumors. Prognosis is poor, mainly due to multimetastatic disease.