CYTOLOGICAL EXAMINATION OF THYROID NEOPLASMS IN INDIGENOUS RESIDENTS LIVING IN THE FORMER SEMIPALATINSK NUCLEAR TEST...

The Semipalatinsk Nuclear Test Site (SNTS) was a major source of radiation exposure for the population of East Kazakhstan between 1949 and 1989. Ionizing radiation is known to have significant mutagenic effects on thyroid tissue, increasing the incidence of benign and malignant thyroid neoplasms. This study analyzes the cytological features of thyroid nodules among native residents of radiation-affected areas and evaluates intergenerational differences in disease prevalence.

To assess the diagnostic value of fine-needle aspiration biopsy (FNAB) in identifying benign and malignant thyroid lesions among populations exposed to chronic radiation and to investigate the cytomorphological patterns associated with each generation of residents.

A retrospective cross-sectional analysis was conducted on 134 native patients from high-radiation-risk areas of East Kazakhstan who underwent ultrasound-guided FNAB between 2013 and 2023. Clinical, ultrasound, and cytological data were evaluated, with generational stratification based on birth year in relation to periods of nuclear testing.

A total of 134 patients were included in the study, with 92.5% females (n=124) and 7.5% males (n=10). The majority of patients were of Kazakh ethnicity (60.4%, n=81), with the remainder belonging to other ethnic minorities, predominantly of Slavic origin (38.8%, n=52). The mean age was 63.98±12.6 years. Based on fine-needle aspiration biopsy (FNAB), the diagnoses were as follows: papillary thyroid carcinoma (PTC) - 42 cases (31.3%), suspicion of PTC - 40 cases (30.1%), follicular adenoma - 45 cases (33.8%), follicular variant of PTC (FVPTC) - 6 cases (4.5%), and medullary carcinoma - 1 case (0.8%). The highest incidence of malignant lesions was observed in the first generation (born 1949-1962), which correlates with higher radiation exposure during atmospheric nuclear testing. The second generation (born 1963-1983) showed a moderate decline in malignancy rates, though the risk remained elevated. The third generation (post-1983) exhibited minimal incidence of malignancy, but a notable increase in benign lesions, such as follicular adenomas, potentially due to residual radiation exposure.

The findings underscore the long-term impact of radiation exposure on thyroid pathology in affected populations. FNAB remains a highly effective diagnostic tool, especially when combined with ultrasound criteria. Intergenerational analysis supports a radiation dose-dependent relationship in the development of thyroid malignancies, with implications for screening and preventive strategies in high-risk regions.