Malignant neurogenic tumor of the heart.

This is the first report of the fine structure of a malignant neurogenic tumor in the heart. The tumor, arising in the infundibulum of the right ventricle of the heart, was resected and examined by both light and electron microscopy. The histologic appearance of the originally resected tumor was consistent with that of a neurofibroma, while that of the recurrent tumor suggested a malignant schwannoma. Ultrastructurally, the presence of basement membrane investing some cells confirmed the neurogenic nature of the tumor. The discontinuous nature of the basement membrane in these cells may provide a clue as to the malignant nature of this tumor.