Morphological and Morphometric Analysis of Follicular Nodular Disease and Follicular Adenoma of the Thyroid Gland as a Rationale for Polarization-sensitive Changes
Year: 2026
Type: article
Abstract: Nodular pathology of the thyroid gland is one of the most common morphological changes of its parenchyma. Due to the widespread use of ultrasound examination, nodular formations are detected in approximately 40–50% of the adult population, the vast majority of which are benign. Follicular adenoma and follicular nodular disease are of particular importance, the modern concepts of the morphogenesis of which have undergone significant changes. The morphological similarity of follicular adenoma, nodular disease, and other follicular neoplasms complicates their differential diagnosis, especially with follicular carcinoma. Since its main criteria are capsular and/or vascular invasion, detailed histological and morphometric examination is of great importance. In this regard, a comprehensive study of the structural organization of follicular adenoma and follicular nodular disease, their cellular, follicular, and stromal-vascular components is relevant for deepening the understanding of the mechanisms of formation of nodular formations and improving the criteria for their differential diagnosis. Objective. To perform a comparative morphological and morphometric analysis of histological specimens of tissue samples of follicular adenoma and follicular nodular disease of the thyroid gland. Material and methods. To conduct our morphological and morphometric study, surgical material consisting of both benign and malignant neoplasms of the thyroid gland was analyzed. All cases of nosological entities were verified according to the current classification of thyroid gland tumors of the World Health Organization (WHO Classification of Endocrine and Neuroendocrine Tumours, 5th Edition) and classified according to the current TNM system. The material for the study consisted of histological specimens made from thyroid gland tissue in follicular adenoma and follicular nodular disease. To assess morphological changes, the standard method of staining with hematoxylin and eosin was used, and for the detection and detailed analysis of fibrous structures of the thyroid gland parenchyma, Van Gieson staining was used. Results. The main histological component of the adenoma was colloid, which in most cases evenly filled the parenchyma of the nodule over its entire area, did not contain any fibrillar structures (except for scant stromal interfollicular elements), and was characterized by low optical anisotropy, which, in turn, formed a relatively weak polarization signal and could be used as an internal reference in assessing changes in the stromal component of the nodular formation. Secondary changes of the nodule in the form of hemorrhages, focal hyalinosis or fibrosis, cystic transformation, etc., did not determine the general nature of the optical signal and could be the cause of the formation of local heterogeneities on PC-OCT images. In contrast to follicular adenoma, the distribution of the stromal component throughout the thyroid gland parenchyma was diverse and with different intensities. In 6 cases, pronounced fibromatosis of the internodular stromal component was noted, which, in isolated cases, was accompanied by processes of hyalinization. Such changes were observed in nodules with a fairly long course of the disease. According to the above-mentioned morphological parameters, follicular nodular disease, as a result of PC-OCT imaging, would predictably be characterized by greater heterogeneity compared with follicular adenoma, the absence of a clear peripheral capsule, high spatial variability of birefringence, and different levels of polarization contrast. Table 2 presents the frequency of detection of the main morphological features in follicular nodular disease of the thyroid gland. Conclusions. 1. In relation to follicular adenoma, follicular nodular disease does not have a homogeneous spatial organization in the context of the surrounding thyroid gland parenchyma due to the absence of a distinct capsule, the formation of follicles of various sizes and configurations, and the presence of heterogeneity of the stromal component in combination with secondary changes of the parenchyma, thus forming a complex polarization pattern. 2. From our point of view, the greatest influence on PC-OCT parameters is exerted by the following morphological criteria: a. Uneven distribution of collagen fibers in the internodular stromal component; b. Foci of fibrotic and hyalinization changes, which locally increase birefringence; c. Combination of macrofollicular and microfollicular areas, which creates heterogeneity of light scattering; d. Large accumulations of colloid with low anisotropy; e. Presence of cystic cavities, which form areas of a sharp decrease in signal intensity; f. Presence of secondary changes in the form of hemorrhages and hemosiderin deposition, which may locally change the scattering coefficients; g. Presence of calcifications, which manifest themselves as local areas of intense scattering.
Authors: O.V. Bilookyi, V.V. Bilookyi, D.V. Proniaiev
Language: English
Subfield: Endocrinology, Diabetes and Metabolism
Field: Medicine
Domain: Health Sciences
Open Access status: diamond
OpenAlex ID: W7222332007