Diffuse sclerosing variant is a major subtype of papillary thyroid carcinoma in the young

Background: Pediatric thyroid cancer differs from adult thyroid cancer in presentation and outcome. Pediatric thyroid cancer has a higher recurrence rate and greater percentage of lymph node and pulmonary metastasis. The clinicopathologic characteristics of pediatric thyroid cancer according to the histologic subtype have not been reported, however. In this study, we determined the histological subtypes of pediatric thyroid cancer and analyzed other clinicopathologic characteristics. Methods: All patients with thyroid cancer who were admitted to Severance Hospital, Seoul, South Korea, were retrospectively reviewed; their age was <20 years at diagnosis, and they were seen between January 1995 and August 2008. Results: Sixty-eight patients were identified. The histologic types of thyroid carcinoma were papillary thyroid carcinoma (PTC) in 57 (83.8%), follicular carcinoma in 8 (11.8%), and poorly differentiated carcinoma in 3 (4.4%). There were 28 (41.2%) cases of diffuse sclerosing variant of papillary carcinoma (DSVPC), 26 (38.2%) of conventional PTC, 2 (2.9%) of follicular PTC, and 1 (1.5%) cribriform-morular PTC. In patients with PTC, there was a higher incidence of bilateral thyroid involvement (p=0.003), extrathyroidal extension (p=0.009), and lymph node involvement (p=0.018), and lower recurrence-free survival (p=0.032) in DSVPC than in non-DSVPC. Univariate regression analysis revealed that extrathyroidal extension (p=0.025) and tumor size (p=0.001) were positively associated with a shorter time to recurrence. Conclusion: DSVPC is a major subtype of PTC in the young.