[Familial adenomatous polyposis with papillary thyroid cancer:a case report].

The patient is 36-year-old woman who complained of proptosis and was diagnosed as thyroid cancer. The pathologic diagnosis of her resected specimen was papillary thyroid cancer, cribriform morular variant (CMV). Subsequently, she was suspected of having familial adenomatous polyposis (FAP), although she had no family history of it. The diagnosis of FAP was confirmed following colonoscopy, which showed multiple polyps, and the biopsies that revealed multiple adenomas and cancers with APC gene mutation. She underwent restorative proctocolectomy, rectal mucosectomy with ileal pouch anal anastomosis, and ileostomy in our department. Cancer in the adenomas was found in four polyps on histopathological examination. CMV is known to be complicated with FAP. However, the number of reported cases remains few. This case was relatively rare, with an initial diagnosis of FAP because of the coexistence of CMV. In patients with papillary thyroid cancer (CMV type), colonoscopy should be considered because of the possibility of FAP.