Solitary thyroid metastasis from colon cancer: a rare case report

Recurrent Metastatic Colorectal Adenocarcinoma to the Thyroid Gland Presenting With Vocal Cord Paralysis and Inspiratory Stridor

The most common sites for metastases of colorectal cancer include the liver, lungs, brain, and regional lymph nodes. However, a limited number of reported cases describe colon cancer metastasis to the thyroid gland. Metastatic colorectal adenocarcinoma to the thyroid gland is rare. The majority of these cases with colon cancer metastases to the thyroid gland are diagnosed years after initial treatment of colon cancer. The discovery is usually made after routine surveillance imaging, and often patients have minimal or absent symptoms. We report a case of a recurrence of metastatic colorectal adenocarcinoma to the thyroid gland presenting with vocal cord paralysis and inspiratory stridor.

Colorectal cancer metastases in thyroid: case report and literature review

BACKGROUND

The thyroid gland is an uncommon site for metastatic deposits from non-thyroid malignancies, occurring in only 1.4 - 3% of surgical specimens where malignancy is suspected. It is even rarer for the source of thyroid metastases to be of colorectal origin. In most cases reported, colorectal metastases in the thyroid occurs many years later after the primary colorectal cancer has been diagnosed and treated. In this unique case, a primary sigmoid carcinoma metastasised to the thyroid gland and presented synchronously as a thyroid nodule.

CASE PRESENTATION

We describe a case of a 64-year-old Caucasian woman who presented with clinical features of metastatic cancer of unknown origin. Her medical history included underlying hyperthyroidism. She had a large pelvic mass adjacent to the sigmoid colon, a left lower lobe lung mass and a suspicious nodule in the left thyroid lobe. A fine-needle aspiration biopsy of the thyroid nodule was performed, which remarkably showed malignant cells originating from primary colorectal cancer on immunohistochemical staining. The patient was managed with palliative chemotherapy given the poor prognosis due to disseminated colorectal malignancy.

CONCLUSIONS

Colorectal adenocarcinoma metastases can rarely present as a metastatic thyroid nodule. Fine-needle aspiration should be performed in suspicious thyroid nodules and may be the least invasive way of identifying a metastatic colorectal or other non-thyroidal malignancy in patients presenting with an unknown primary. The pathologist should be vigilant to this possibility and specific immunohistochemical markers should be used to ensure accurate diagnosis. In thyroid metastases, the prognosis is ultimately determined by the primary tumour but thyroidectomy still has a role in alleviating compressive symptoms and can potentially improve survival in selected cases.

A case of metastatic rectal adenocarcinoma diagnosed by thyroid cytology

Fine-needle aspiration (FNA) cytology of the thyroid gland has been widely used for the evaluation of thyroid nodules. Most of the nodules are primary thyroid lesions. However, up to 4% of thyroid FNA may harbor a metastatic neoplasm. The metastases are most commonly from lung, kidney, breast, and skin. Metastatic colorectal cancers are also seen in thyroid but less common. Here we report the cytologic features, differential diagnosis and clinical implications of a metastatic rectal adenocarcinoma to the thyroid gland diagnosed by FNA.