Diagnosis: Adenocarcinoma of the colon with metastasis to the thyroid gland (TM)
Clinically significant TMs are extremely rare, affecting less than 1% of patients undergoing thyroidectomy and only 0.07% of those evaluated with FNA biopsy.1However, the overall incidence of a secondary malignant neoplasm varies, ranging from 1% in an unselected autopsy study to 24% in patients who eventually died of widespread disease.1-3In postmortem series, breast and lung carcinomas are the most frequent primary tumors; whereas renal cell carcinoma is the most common site of origin in a number of clinical reviews.2,4,5Also, several Asian series have demonstrated a significant percentage of thyroid involvement from primary tumors of the gastrointestinal system (eg, the esophagus and colon).3