Calretinin as a marker for cardiac myxoma - Diagnostic and histogenetic considerations

To study the usefulness of calretinin as an immunohistochemistry marker in the diagnosis of cardiac myxoma (CM) and the origin of myxoma cells, eve ex amined 24 CMs and 9 fetal hearts with immunohistochemical methods on formal in-fixed paraffin-embedded tissues. We compared 24 CMs with 10 mural thromb i, 6 jaw myxomas, and 2 papillary fibroelastomas. Calretinin expression was identified in 100% of CMs and was negative in all cases of mural thrombi, jaw myxoma, and papillary fibroelastoma. Calretinin expression by the neopl astic cells in CM was strong and diffuse and had a cytoplasmic and a nuclea r pattern. Calretinin expression in fetal hearts was found in autonomic gan glia cells in the subepicardial tissue of the atria and atrial appendages, along the interatrial ann atrioventricular sulci, and in the atrial septum. Results clearly indicate that calretinin can be used as a marker for the d iagnosis of CM and that it is a powerful tool for the differential diagnosi s, most importantly with mural myxoid thrombi. Furthermore, the positive ex pression of calretinin by the autonomic neurons in the fetal heart and CM s upports the concept that myxoma cells may originate from endocardial sensor y nerve tissue.