A rhabdomyoma is a benigntumor of striated muscle. Rhabdomyomas may be either "cardiac" or "extracardiac" (occurring outside of the heart). Extracardiac forms of rhabdomyoma are subclassified into three distinct types: (1) Adult type, (2) Fetal type, and (3) Genital type.
Cardiac rhabdomyomas are the most common primary tumor of the heart in infants and children. It has an association with tuberous sclerosis. In those with tuberous sclerosis, the tumor may regress and disappear completely, or remain consistent in size.
^Edward F. Goljan (2009). Pathology, Third Edition (in English). Elsevier. p. 537. "Tumour Type: Rhabdomyoma; Location: Heart, also tongue and vagina; Comment: Benign heart tumour associated with tuberous sclerosis"