Ultrastructural and Immunohistochemical Contribution to the Histogenesis of Human Cardiac Myxoma

Abstract

The ultrastructural features of 8 human cardiac myxomas were analyzed and correlated with immunohistochemical data, with the aim to clarify the characteristics of the cell lines involved in the tumor genesis. Immunohistochemical studies were performed to detect the presence and the distribution of intracytoplasmic filaments (vimentin, desmin, actin, myosin) as well as myoglobin and factor VIII-related antigen, albumin, and lysozyme. Eighty percent of myxoma cells were simultaneously positive for vimentin, desmin, and actin, whereas 30% of them stained with antifactor VIII and antivimentin antibodies. The submicroscopic analysis revealed two main cell populations: (1) one composed of stellate-shaped cells with scanty organelles and sparse hyaloplasmic filaments scattered throughout the myxoid stroma and forming a loose network with their projections; (2) another one included cells with more cytoplasmic organelles, intermediate filaments, and myofilaments arranged either singly or in both solid and hollow cord-like structures. Our results support the hypothesis that cardiac myxoma may originate from a reserve multipotent mesenchymal cell able to differentiate more or less completely along two major evolutional lines: myoid and endothelial. The tumor tissue thus seems to be involved in vessel formation, suggesting a growth pattern akin to that manifested in other forms of endocardial pathological reactivity in which reserve mesenchymal cells are engaged.

A novel kind of tumor type-characteristic junction: plakophilin-2 as a major protein of adherens junctions in cardiac myxomata

“…Nonmuscle-type actin microfilaments are prevalent, but in a minor proportion of myxoma cells we have also detected a-smooth muscle-type actin filaments but no sarcomeric a-actins. All our general immunocytochemical observations in the 32 myxomata studied are grosso modo in agreement with most previous reports, indicating a derivation from cardiac mesenchymal cells [20][21][22][23][24][25][26][27][28][29] (for occasional claims of special cardiac myxoma tumor cells showing keratin reactions, mostly in glandular elements, see references 24,29,30).…”

Cardiomyogenic Differentiation in Cardiac Myxoma Expressing Lineage-Specific Transcription Factors

“…Previous studies to identify the cells of origin of cardiac myxomas using immunohistochemistry, electron microscopy, and tissue culture have yielded conflicting results. [3][4][5][6][7] Differentiation toward endothelial, [3][4][5][6] fibroblastic, 5 and smooth muscle cells, 3,5 along with typical stromal cells, has been identified in cardiac myxoma, and glandular differentiation has rarely been observed. 5,7 Neurogenic differentiation has also been suggested based on the findings of S100 protein and neuron-specific enolase immunoreactivity in some tumor cells.…”

“…5,7 It is now believed that they may develop from primitive, reserve multipotential mesenchymal cells that are capable of several types of differentiation. [5][6][7] A recent genetic analysis of the embryonic patterning in the fruit fly led to the identification of the homeobox or Hox genes, 8 which are encoding transcription factors, that appear to specify the formation of segmental structure along the A/P axis of embryos. Nkx2.5/Csx, is one of the mammalian homologues of tinman, a Drosophila homeobox gene required for the specification of cardiac precursor cells and for morphogenesis of the heart.…”

“…The cells giving rise to the tumors are considered to be mesenchymal cells that persist as embryonal residues 4 -7 during septation of the heart and may later differentiate into cardiomyocyte precursor cells along with endothelial, [3][4][5][6] fibroblastic, 5 neurogenic, [5][6][7] and smooth muscle cells. [3][4][5] We agree that the identification of tumor origin by specific antigen expression may be misleading, because the phenotypic expression in neoplasia can be variable and does not necessarily reflect its origin.…”

An unusual marrow transplant complication: cardiac myxoma

“…Cardiac myxoma is a rare form of heart tumor whose origin is still under discussion. 3,4 Here, we report the occurrence of a right atrial myxoma in a young thalassemic patient in the early period after BMT.…”