Age- and Gender-Specific Risk of Thyroid Cancer in Patients With Familial Adenomatous Polyposis

Context: The cribriform-morula variant of papillary thyroid carcinoma (CMV-PTC) is a rare variant of PTC and is associated with familial adenomatous polyposis (FAP). However, the incidence and the nature of CMV-PTC among FAP patients have not been well characterized. Objective: The aim of this study was to determine the incidence and characteristics of thyroid cancer screened by neck ultrasonography for FAP patients. Design, Patients, and Intervention: A total of 129 FAP patients were included in this study. Neck ultrasonography was performed using a 12.0-MHz transducer probe. Germline APC gene mutation was examined for by the protein truncation test or DNA sequencing methods. Results: Twenty-one patients (16.3%) had solid nodules, and 24 patients (18.6%) had benign cystic nodules. In total, PTC was found in 11 patients (16% of the women and 0% of the men), 8 of which were CMV-PTC and the rest were classical PTC. In 17 female patients with thyroid nodules, CMV-PTC occurred in 8 of 9 patients who were 35 years age or younger but in none of the 8 patients who were older than 35 (P = .0004 by Fisher’s exact test). The APC germline mutations in 8 patients with CMV-PTC were present at the 5′ side of the profuse type of FAP region (codons 1249–1330). Conclusions: The prevalence of CMV-PTC in FAP patients was higher than previously reported and this type of tumor was found preferentially in younger (under age 35) female patients with FAP in this cohort.