The purpose of the investigation was to study the morphological variants and molecular changes of the endothelial component of adenomyosis (AM) concurrent with endometrial adenocarcinoma (EAC). Monoclonal and polyclonal antibodies to ApoCas, Cl 2, 3, and 5, Ki-7, MMP-2, MMP-9, TIMP-1, E-cadherin, COX-2, EGFR, and VEGF were used as primary antibodies. The AM foci displayed the following types of epithelial changes: the epithelium corresponding to the proliferation stage; epithelial hyperplasia with and without atypia; atrophic epithelium. There was an increased expression of ApoCas, Ki-67, MMP-2, MMP-9, COX-2, VEGF, and EGFR, which increased from proliferation to hyperplasia with atypia. The maximum expression of the markers was seen in EAC. The foci of AM, which corresponded to epithelial hyperplasia with atypia, were characterized by the oncomarker changes supporting its malignant potential: elevated Ki-67 and EGRF, reduced E-cadherin, changes in MMP-2, MMP-9, TIMP-1, and claudins-2, -3, and -5.