Clinical features of papillary thyroid carcinoma associated with familial adenomatous polyposis

Patients with familial adenomatous polyposis (FAP) are at an increased risk for thyroid cancer. FAP is known to be associated with a distinct histologic subtype of papillary thyroid carcinoma (PTC), the cribriform variant. We report the case of a 39-year-old female patient who had been diagnosed as having FAP when she was 18 years old and undergone total colectomy. Because she had nodules in the right lobe of the thyroid, a right thyroid lobectomy was performed at the same time. Twenty years later, she was detected to have polyps in the rectum, and a CT revealed nodules in the left lobe of the thyroid. Ultrasound revealed two well-circumscribed nodules with a smooth margin; fine needle aspiration cytology revealed Class IV cytology and PTC was suspected. A left thyroid lobectomy with paratracheal neck dissection was performed. Macroscopically, the resected specimen showed multiple white encapsulated nodules with well-defined borders. The histopathological diagnosis was papillary carcinoma, cribriform variant; there was no lymph node metastasis. Because the ultrasonographic findings and macroscopic findings of the specimen were unusual for PTC (the common ultrasound findings are a hypoechoic texture, microcalcifications, and irregular margins), we reviewed the Japanese literature. We found 22 reports in the literature, with 24 cases of PTC associated with FAP. The ultrasonographic findings were described in 6 cases, and in all 6, the lesion was well-circumscribed with a smooth margin, mimicking the common findings of follicular tumors. The macroscopic findings were available for 18 cases and in all of them, the findings were consistent with those of encapsulated PTC. Although regular ultrasonographic screening of the thyroid is recommended for patients with FAP, we must be careful to not look out for the common findings of PTC, but for well-circumscribed nodules with a smooth margin.