Myxosarcoma of the right ventricle: an immunohistochemical and ultrastructural study.

Background: Myxosarcoma is an unusual form of primary cardiac malignancy with few reports in the literature. Although these tumours occur in a similar anatomical distribution to cardiac myxoma, the relationship between these two tumours is uncertain due largely to the limited studies available that characterise the morphological features of myxosarcoma.

Materials And Methods: The clinical and pathological features, including immunohistochemical and ultrastructural studies of cardiac myxosarcoma, in a 58-year-old male who died eight months after onset of symptoms are reported.

Results: At presentation the tumour was sited in the right ventricle and at post-mortem was found to have extended into the right atrium, pulmonary infundibulum, pulmonary artery, pericardium and pleural cavities. Histologically the tumour was composed of spindle and stellate cells within a myxoid stroma. Ultrastructural studies showed abundant intermediate filaments and vacuoles within the tumour cell cytoplasm, without any evidence of muscle differentiation. Immunohistochemical staining for vimentin and myoglobin was positive, while there was negative expression of desmin, smooth muscle actin, factor VIIIa, CD34, CD68, S-100 protein, bcl-2 and for epithelial markers.

Conclusion: Comparison of the morphological findings from the present case with the limited data available suggests that myxosarcoma is not a single tumour entity but a group of tumours of diverse histogenesis.