A Rare Case of Thyroid Metastasis from Rectal Adenocarcinoma

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    Background: Metastasis from non-thyroid malignancies to the thyroid gland is rare and is most commonly from lung and renal cell carcinoma. We report the case of a patient with a history of rectal adenocarcinoma which metastasized to the thyroid.

    Clinical Case: A 64 year old female was referred to the ENT clinic with a U4 thyroid lesion to the right lobe. Four years previously, she had been found to have a Dukes C1 adenocarcinoma of the rectum. An ultra low anterior resection with colo-anal pull through anastomosis was performed with final histology of pT3pN2. She underwent adjuvant chemotherapy but was unable to complete her treatment due to toxicity. Three years later, a follow up PET scan revealed a left lower lobe lung lesion, for which the patient underwent a left lower lobectomy, and a thyroid lesion. Core biopsy of the thyroid lesion showed metastatic adenocarcinoma of rectal origin. A total thyroidectomy was performed with no complications. Histological examination showed R1 margins extending to the tracheal margin. No adjuvant therapy was given. During subsequent follow up, brain metastases were found and the patient was treated with stereotactic radiotherapy.

    Conclusions: Although metastases to the thyroid are rare, they should be considered in patients with a thyroid nodule and a history of malignancy. There is no clear recommendation for the management of metastasis to the thyroid gland including the extent of surgical resection.


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