Left ventricular mesenchymal hamartoma, a new hamartoma of the heart.

Primary neoplasms of the heart are rare. Benign entities in adult populations include myxoma, fibroma, lipoma, hamartoma of mature myocytes, and vascular hamartoma. The most common pediatric cardiac neoplasm is the rhabdomyoma. We report a 22-year-old female with a primary left ventricle tumor composed of multiple mature mesenchymal tissues, including mature cardiac myocytes, smooth muscle, fibroblasts, fat, blood vessels including a hemangioma like area, and nerve fibers. The various elements were disorganized, but well differentiated, and showed little mitotic activity, which are features suggestive of a hamartoma. Unlike a cardiac fibroma, which may entrap myocardium at the periphery of the lesion, the present case demonstrated all tissue elements throughout the tumor mass. We suggest that this lesion is sufficiently different from those hamartomas previously described to warrant a new designation, for which we propose the title cardiac mesenchymal hamartoma.