Thyroid metastasis from rectal adenocarcinoma.

The thyroid is a rare site for metastasis, occurring in 0.1% of colorectal cases. A 46-year-old man with rectal adenocarcinoma developed an enlarging anterior neck mass and increasing carcinoembryonic antigen 2 years after curative intent treatment. Imaging showed aggressive features with invasion of the larynx, trachea and oesophagus, suspicious for anaplastic thyroid carcinoma. The patient underwent tumour debulking with neck dissection and tracheostomy. Final histopathological review revealed metastatic adenocarcinoma from a colorectal primary. Despite chemotherapy, the patient eventually succumbed to disease progression and complications of his illness. This case demonstrates that recognising rare sites of metastasis may help clinicians effectively institute earlier intervention.