Epithelioid leiomyosarcoma of the left atrium: immunohistochemical and ultrastructural findings.

Leiomyosarcomas of the heart are rare, with only 12 cases reported in the literature. An example of the epithelioid variant of leiomyosarcoma is described. The tumour cells expressed vimentin, desmin, muscle-specific actin and smooth muscle-specific actin. In addition, they were also labelled by monoclonal and polyclonal antibodies to cytokeratin intermediate filaments and displayed cell junctions at the ultrastructural level, features which highlight the potential pitfalls in the application of immunohistochemistry and electron microscopy in the diagnosis of poorly differentiated tumours.