Benign lipomatous masses of the heart: a comprehensive series of 47 cases with cytogenetic evaluation.

Benign lipomatous lesions of the heart encompass an apparently etiologically diverse group of entities including neoplastic, congenital, and reparative phenomena. Among these, lipomas and lipomatous hypertrophy of the atrial septum (LHAS) represent 2 commonly encountered mass lesions. To date, no study has systematically and comparatively evaluated the morphologic and genetic characteristics of these lesions. Tissue registry archives of Mayo Clinic were queried for cases of cardiac lipoma and LHAS (1994-2011). Clinical, imaging, and pathologic findings were reviewed. Representative cases in each cohort were evaluated by fluorescence in situ hybridization (FISH) for HMGA1 and HMGA2 loci rearrangement and for MDM2/CPM locus amplification. Five cases of cardiac lipoma were identified (mean age, 67 years; range, 48-101; 3 men): 4 right atrial and 1 left ventricular. Forty-two cases of LHAS were identified (mean age, 75.6 years; range 45-95; 20 men), 39 of which were autopsy derived. The median size was 3.4 cm for lipomas and 2.8 cm for LHAS (n = 14). A single case each of cardiac lipoma and LHAS were found to harbor HMGA2 rearrangement, whereas no case showed cytogenetic abnormality of HMGA1 or CPM. This represents the largest series of histopathologically confirmed cardiac lipomas from a single institution. In addition, it is the first to evaluate cardiac lipomas and LHAS for genetic alterations associated with extracardiac lipomatous lesions. The genetic and morphologic similarities found provide evidence in support of the neoplastic classification of cardiac lipomas. A single case of LHAS contained an HMGA2 rearrangement, challenging the currently accepted hypothesis of pathogenesis for this lesion.