THE IMPORTANCE OF PREOPERATIVE CYTOLOGICAL DIAGNOSTICS IN FULFILLING THE TASKS OF THE UKRAINIAN-AMERICAN PROJECT FOR STUDING CANCER AND OTHER THYROID DISEASES IN UKRAINE CAUSED BY THE CHORNOBYL ACCIDENT

Abstract

The largest man-made disaster of human history in 1986
at Chornobyl Nuclear Power Plant (ChNPP) resulted in a massive release
of significant amounts of radioiodine into the atmosphere and
the irradiation of a large population. This event provided a unique
opportunity to study the impact of ionizing radiation on human
health. The main long-term consequence of the Chornobyl accident
was a sharp increase in thyroid cancer incidence among residents
of radioactively contaminated areas of Ukraine, which prompted a

number of domestic and international studies. To study the effects
of radiation exposure, SI «Komisarenko Institute of Endocrinology
and Metabolism of the National Academy of Medical Sciences of
Ukraine» and the National Cancer Institute of USA launched the
«Ukrainian-American Research Project for the Study of Thyroid Cancer
and Other Diseases in Ukraine as a Result of the Chonobyl Accident
». The aim of our work was to evaluate the contribution of
preoperative cytological diagnostics to the effectiveness of monitoring,
diagnosis and treatment of thyroid tumors, namely papillary
thyroid carcinoma (PTC) in patients from the Ukrainian-American
Project cohort. Material and methods. All sonographically suspicious
thyroid lesions were referred for fine-needle aspiration biopsy
(FNAB) followed by cytological examination. The punctures were
fixed in methanol and stained according to Romanovsky-Giemsa.
Cytological reports were formed using the Bethesda cytology reporting
system. Results. Between 1998 and 2023, within the framework
of the Ukrainian-American Cohort Study, postoperative histopathology
revealed PTC іn 197 operated cohort members who underwent
preoperative FNAB. In 81.7% of these patients, cytological testing
also revealed PTC or a suspicion of it, and in 14.72%, follicular neoplasia
was cytologically detected. Depending on whether the cytological
interpretation of follicular neoplasia was considered «positive»
or «negative», the sensitivity of cytological detection of PTC in the
thyroid was 96.4% and 81.7%, respectively. No differences in the cytomorphological
characteristics of PTC were found between patients in
the cohort and territories free from radiation contamination. Analysis
of the micronuclei frequency in thyrocytes from PTC punctates from
patients with radioactive iodine-contaminated and from «clean» areas
revealed no statistically significant difference, demonstrating absence
of a relationship between radioactive iodine exposure and the appearance
of micronuclei in PTC epithelial cells. Analysis of the frequency
of micronuclei in punctate thyrocytes of PTC patients revealed
no relationship between radioactive iodine exposure and the appearance
of micronuclei in PTC epithelial cells. A significant statistically significant
difference in the frequency of micronuclei was demonstrated
between PTCs and benign A-cell nodules (p < 0.01). These results
suggest that micronuclei can be used as a marker of epithelial malignancy
in cases where cytological diagnosis is challenging and where
cytoplasmic pseudoinclusions within the nucleus are absent. Conclusions.
The sensitivity of cytological detection of thyroid PTC in the
Ukrainian-American Thyroid Cancer Cohort Study for the period 1998-
2023 was 96.4% and 81.7%, respectively, depending on whether the
cytological interpretation of follicular neoplasia was considered «positive
» or «negative». Analysis of cytological preparations from patients in
the cohort and from patients in unaffected areas revealed no differences
in cytomorphological characteristics, including the presence of
micronuclei in PTC. Micronuclei cannot be considered as a marker of
«radiation carcinomas», but they can be used as a cytological marker
of A-cell malignancy, since there is a statistically significant increase in
their number of PTC.