Colorectal cancer metastases to the thyroid gland: A case report

BACKGROUND: Secondary malignancies of the thyroid gland are a rare finding in clinical practice. In addition, colorectal metastasis to the thyroid (CMT) is even more infrequently diagnosed. The source of the primary tumor follows demographic and ethnic patterns, which reflects the most prevalent malignancies in the different populations. Colorectal cancer is one of the most common types of cancer worldwide; nevertheless, CMT is infrequently diagnosed. Most of them are identified during the follow-up of gastrointestinal primary malignancies. Due to the improvement of image techniques, oncological treatment, and follow-up, survival and consequent diagnosis of metastatic disease are more frequent. Those facts make this entity a diagnostic and therapeutic challenge, due to the lack of information and the difficulties performing clinical trials and research. CASE SUMMARY: Here, we present a case report of a patient diagnosed with CMT of adenocarcinoma of the rectum evidenced during follow-up, 4 years after neoadjuvant chemoradiotherapy, who had subsequent curative surgical treatment of the primary tumor and inter-current lung bilateral metastases. CONCLUSION: Thyroid metastases of extra-thyroid origin are an uncommon finding, even rarer in cases of CMT. The diagnostic process, as well as survival of oncologic patients is improving, and consequently the number of metastases to the thyroid gland is increasing.