A. Zborovskaya

BACKGROUND: A systematic analysis of the clinical and pathologic patterns of childhood "sporadic" thyroid carcinoma in Belarus, in the absence of the "Chernobyl radioactive iodine factor," has never been performed. The aim of this study was to establish the essential features of "sporadic" papillary thyroid carcinoma (PTC) in Belarusian children and adolescents, and the relationship of tumor pathology to extrathyroidal extension (ETE) and lymph node metastases. METHODS: This was a retrospective population-based study with assessment of histological samples of 119 cases of thyroid cancer in Belarusian children and adolescents of 0-18 years old registered during 2005-2008 years. Sporadic PTC was noted in 94 children who were not exposed to the Chernobyl radiation release. None of the 119 cases of thyroid were follicular thyroid cancer. RESULTS: The incidence rate of PTC was 1.13 per 100,000 persons. The median age at diagnosis was 15.1 years with fourfold predominance of diagnosis in female patients. Relapse was detected in 2% of cases with median follow-up of 4.2 years. Median tumor size was 12 mm. Three percent of the cases of PTC had multifocal growth. The classical variant of PTC was registered in 46% of the patients with thyroid cancer, the follicular variant of PTC was noted in 20% of the cases. The percent of rare types of PTC (tall cell and diffuse sclerosing) were equal to that for solid PTCs (13%, 12%, and 10%, respectively). Adolescents had a pure papillary carcinoma more often compared to children who represented tumors with mixed papillary/follicular patterns more frequently (p<0.05). Two-thirds of the patients with PTC had regional lymph node metastases. ETE was established in 39 of 74 patients in whom ETE could be assessed by morphology. Multivariate analysis showed that lymphatic invasion was the strongest independent factor associated with both ETE (p<0.0001) and lymph node metastases (p<0.0001). CONCLUSION: In 2005-2008, sporadic thyroid cancer in children of Belarus was represented by high prevalence of PTC and absence of follicular thyroid cancer. Sporadic cases of PTC in Belarus were characterized by smaller tumor size, a small number of cases with multifocal growth, an equal number of rare types and solid PTCs, a relatively high prevalence of pure papillary variant of PTC in adolescents, and a low frequency of early relapses. A high frequency of ETE and lymph node metastases was detected. The strongest morphologic factor associated with both of them was lymphatic invasion.

Neuroblastoma comprises the most common neoplasm during infancy (first year of life). Our study describes incidence of neuroblastoma in Southern-Eastern Europe (SEE), including - for the first time - the Nationwide Registry for Childhood Hematological Malignancies and Solid Tumors (NARECHEM-ST)/Greece, compared to the US population, while controlling for human development index (HDI). Age-adjusted incidence rates (AIR) were calculated for 1,859 childhood (0-14 years) neuroblastoma cases, retrieved from 13 collaborating SEE registries (1990-2016), and were compared to those of SEER/US (N = 3,166; 1990-2012); temporal trends were assessed using Poisson regression and Joinpoint analyses. The overall AIR was significantly lower in SEE (10.1/million) compared to SEER (11.7 per million); the difference was maximum during infancy (43.7 vs. 53.3 per million, respectively), when approximately one-third of cases were diagnosed. Incidence rates of neuroblastoma at ages <1 and 1-4 years were positively associated with HDI, whereas lower median age at diagnosis was correlated with higher overall AIR. Distribution of primary site and histology was similar in SEE and SEER. Neuroblastoma was slightly more common among males compared to females (male-to-female ratio: 1.1), mainly among SEE infants. Incidence trends decreased in infants in Slovenia, Cyprus and SEER and increased in Ukraine and Belarus. The lower incidence in SEE compared to SEER, especially in infants living in low HDI countries possibly indicates a lower level of overdiagnosis in SEE. Hence, increases in incidence rates in infancy noted in some subpopulations should be carefully monitored to avoid the unnecessary costs health impacts of tumors that could potentially spontaneously regress.