A 58-year-old woman undergoes excision biopsy of a tumor in the left posterior triangle of her neck. Histology suggests that this is a metastatic cancer. What is the most likely site of the primary tumor?

More than 80% of neck gland tumors arise from structures above the clavicle. The piriform fossa is lateral to the aryepiglottic folds and is a major site where a primary cancer may remain hidden from early detection. Twenty percent of neck gland tumors are primary and 80% represent metastatic disease.