Interventricular septal fat-containing mass most consistent with cardiac lipoma in an adult with tuberous sclerosis complex.

Tuberous sclerosis complex (TSC) is a multisystem genetic disorder in which cardiac rhabdomyomas and myocardial fatty foci are recognized cardiac manifestations, whereas discrete cardiac lipoma-like masses are uncommon. We report a 42-year-old woman with genetically and clinically confirmed TSC who underwent contrast-enhanced chest CT for surveillance of pulmonary lymphangioleiomyomatosis. CT demonstrated a well-circumscribed homogeneous macroscopic-fat attenuation mass centered in the mid-to-apical interventricular septum, measuring 2.8 × 2.2 × 2.0 cm with mean attenuation of approximately -92 HU and mild contour bulging toward the right ventricular cavity. The discrete mass-like morphology and homogeneous macroscopic fat favored cardiac lipoma over a typical TSC-associated myocardial fatty focus, although definitive distinction remains limited in the absence of dedicated cardiac MRI or histopathologic confirmation. This case emphasizes the imaging differential of fat-containing myocardial lesions in adults with TSC and the importance of integrating lesion morphology, size, tissue composition, and mass effect rather than relying on septal location alone.