Abstract
BACKGROUND: Metastatic carcinoma of the thyroid gland is a rare encounter in clinical practice, but autopsy series showed that it is not so rare. Thyroid metastasis from colorectal cancer (CRC) is rare and has a poor prognosis. We herein report a rare case of solitary thyroid metastasis from rectal cancer combined with needle tract implantation after fine-needle aspiration (FNA) of the thyroid nodule and review the relevant literature. CASE SUMMARY: A 54-year-old woman with a history of TNM stage III CRC presented a 1.3 cm × 1.0 cm mass in the left thyroid gland. FNA and histological examination of the left thyroid lobe surgical specimen confirmed the diagnosis of isolated metastatic adenocarcinoma from the rectum. Needle tract implantation was observed in the neck 11 mo after the FNA examination. The 2.5-cm seeding lesion was successfully removed by surgery, and the patient recovered well. The literature relevant to this clinical condition, the diagnostic workup, spread pathway, and surgical management of these rare lesions is reviewed. CONCLUSION: For a patient with a thyroid mass and a history of CRC, metastatic thyroid carcinoma should be considered even if the patient has no evidence of other organ metastasis from CRC. FNA cytological examination of the thyroid mass is useful in the differential diagnosis between primary thyroid disease and metastatic thyroid carcinoma. Thyroid lobectomy of the gland containing the metastatic tumor is suggested in patients with metastatic carcinoma of the thyroid.