This study highlights the significance of electron microscopic analysis in diagnosing proliferative changes associated with endometrial cancer, since the cytological investigations utilizing electron microscopy are of considerable scientific and clinical value for identifying atypical cells. Purpose of the study was to assess the diagnostic importance of electron microscopic examination in detecting proliferative alterations in endometrial cancer. Materials and Methods. The research involved 132 patients diagnosed with endometrial adenocarcinoma (main group) and 35 patients with atypical glandular hyperplasia (control group). Surgical specimens obtained from patients with uterine cancer were submitted to the electron microscopy laboratory for examination using both light and electron microscopy techniques. Findings. Atypical glandular hyperplasia is primarily characterized by the formation of basement membrane invaginations, mitochondrial swelling, roughened mitochondrial cristae, and engorgement of interstitial stromal capillaries. In well-differentiated adenocarcinomas, some cells exhibited structural deformation of desmosomes and a reduction in their number. In G2-grade tumors, the number of desmosomes further decreased, while in G3 tumors, the few desmosomes present showed complete disintegration. Less than 20% of cells in well-differentiated adenocarcinomas demonstrated degradation of desmosomes, accompanied by mild nuclear deformation, mitochondrial swelling, and partial fragmentation of mitochondrial cristae. In poorly differentiated tumors, over 50% of cells exhibited complete desmosomal degradation, marked nuclear polymorphism, and total fragmentation of mitochondrial cristae. Conclusion. The findings underscore the utility of electron microscopy in evaluating the morphological features of endometrial tissue, aiding in the prediction of proliferative disease progression in patients.