Myxomas of the heart are one of the most common primary heart tumours, which most often develop in the left atrium, are characterised by a benign nature and no relapses after surgical removal of the tumour. Karney complex is an autosomal dominant disease characterised by numerous tumours, in particular, myxomas of the heart. Insufficient coverage of this pathology in the literature leads to an erroneous diagnosis, progression of the disease and inadequate treatment. The purpose of the study was to determine the morphological features of heart myxomas in patients with Karney complex. Using light microscopy, a morphological examination of the heart myxomas was performed, which were removed during 7 operations. Histological sections were made from the operating material, which were stained with hematoxylin and eosin, according to Van Gieson, fuchselin, and Masson's Trichrome Stain in the Zerbino-Lukasevich modification. A comparison of the group of heart myxomas of patients with the Karney complex (16 tumours) with a group with myxomas of the heart that occur sporadically (278 tumours) was made to identify morphological features. It was established that myxomas of the heart are multiple, they were detected with the same frequency in the right and left chambers of the heart. It was generalised that in myxomas of the heart, signs of both alteration and high proliferative activity of endotheliocytes and fibrous connective tissue cells are noted. Secondary myxomas of the heart in patients with the Karney complex have the same structural organisation as primary tumours, but most often they are not relapses, more often they are multiple and do not have a predominant localisation in the left atrium. The analysis established an identical cellular composition of both groups of heart myxomas, which suggests the same source of tumour growth, but the presence of more complex cell formations in sporadic myxomas and the predominance of single cells in Karney heart myxomas indicate the existence of differences in their morphogenesis
