Papillary carcinoma of the thyroid gland of childhood and adolescence: Morphologic subtypes, biologic behavior and prognosis - A clinicopathologic study of 42 sporadic cases treated at a single institution during a 30-year period

Papillary thyroid carcinomas (PTCs) in pediatric age show an excellent outcome, independently of sex, stage at diagnosis, occurrence of relapse, and type of treatment. Our aim was to study the biologic behavior and the impact on survival of PTC subtypes in childhood. From 1968 to 2002, 42 sporadic pediatric PTCs were subclassified into PTC, not otherwise specified and PTC variants. In all cases, sex, age at diagnosis, age of menarche, side, size, TNM/pTNM classification, neoplastic microfoci, vascular invasion, status of the non-neoplastic parenchyma, and treatment (surgery and nonsurgical therapies) were registered. Follow-up was carried on up to May 2005. PTC, solid/trabecular variant was the most frequent subtype. Both extrathyroid local invasion (P < 0.04) and distant metastases (P < 0.01) at onset were significantly associated with PTC, not otherwise specified. After a median follow-up of 16 years, for the whole series overall survival and progression-free survival (PFS) rates were 100% and 77%, respectively. The solid/trabecular variant was at a significantly increased risk of relapse (PFS 50%, P < 0.01). The occurrence of poorly differentiated tall cell morphology did not influence survival. Sensitivity to hormonal manipulation was maintained over time. In conclusion, although overall survival was not influenced by PTC subtypes, the solid/trabecular variant of PTC was at a significantly higher risk of relapse. At variance with adults, presence of the tall cell morphology did not carry a worst prognostic significance.