Cytokeratin profile and neuroendocrine cells in the glandular component of cardiac myxoma

Glandular cardiac myxomas are very rare tumors of uncertain histogenesis that display glandular structures within otherwise typical myxomatous tissue. The origin of the glands has been attributed to epithelial differentiation of a totipotent cardiomyogenic precursor cell or to entrapped embryonal rests in the tumor. We studied four cases of glandular myxomas (three sporadic and one familial) to define the immunophenotypic profile of the glandular elements. The glands were either single and located within the myxoma cell islands (three cases) or in groups embedded in the myxomatous matrix. In the latter case, the glands featured villous projections, irregular profile, active inflammation or focal reactive cellular atypia (case 3) and had acidic and neutral mucins (mostly sialomucins). The cytokeratin expression profile (cytokeratin 7 and 20 co-expression) was similar to that of foregut derivatives. Scattered chromogranin-positive neuroendocrine cells were observed in case 3. Our findings indicate that the glandular component in cardiac myxoma is morphologically heterogeneous. In some cases, the scattered glands may derive from a divergent (epithelial) differentiation of myxoma cells; in others, entrapment of embryonic gastrointestinal rests (with mature neuroendocrine and mucous cell populations) could be the case.