Thyroid Metastasis of Gastric Cancer: A Rare Occasion With Poor Prognosis

A 68-year-old man was diagnosed as having advanced gastric cancer. Computed tomography showed a thyroid tumor with trachea deviation. This tumor exhibited mosaic echogenecity in ultrasonography. Signet-ring cell carcinoma was found by means of fine needle aspiration biopsy. This tumor gradually became swollen and the thyroid hormone levels in blood were increased without any clinical symptom. Shortly, he died from his illness in the 29th hospital day. Autopsy disclosed that the left lobe of the thyroid gland was highly invaded by malignant cells and that lymphogenic rather than angiogenic metastasis was highly probable. Thyroid metastasis of gastric cancer is extremely rare. The prognosis is very poor. Ultrasonography is a very useful modality especially when coupled with recently developed fine needle aspiration biopsy in differential diagnosis of thyroid tumors once malignancy is suspected. Therapeutic strategy largely depends on the nature of primary malignant tumor. If the tumor is slowly progressive such as renal cell carcinoma and breast cancer, extirpation of thyroid tumors may extend life expectancy. In conclusion, the metastatic thyroid tumor of gastric cancer is rare and shows poor prognosis. Fine needle aspiration biopsy under ultrasonography is strongly recommended as a useful diagnostic tool.