There are large, rounded polygonal cells with strands of cytoplasm interspersed among glycogen-rich vacuoles – “spider cells”.  This tumor is sometimes part of a hamartomatous syndrome, tuberous sclerosis.

A tumor of fetuses and infants, this pathologically benign lesion can kill due to obstruction. It can be located anywhere in the heart but is often in the right atrium. The tumor is a hamartoma and is frequently part of a hamartoma syndrome, tuberous sclerosis (TS). Histological study reveals large, rounded or polygonal, cells with strands of cytoplasm interspersed among glycogen-rich vacuoles. These cells are referred to as spider cells. The inheritance is autosomal dominant. The emergence of TS is de novo in 2/3 of cases. There are defects in tumor suppressor genes, TSC 1 and 2. If the rhabdomyoma is single about 50% have TS. 100% of patients with multiple rhabdomyomas have TS. 47-67% of patients with TS have rhabdomyomas. TS involves other organs as well. Other TS lesions include renal cysts and angioleiomyoma, hypomelanic skin nodules and angiofibromas, and tubers in the CNS. Tubers are histologically benign but can cause seizures or can obstruct the flow of CSF. Patients with cardiac rhabdomyoma should be evaluated for skin, brain or renal manifestations of tuberous sclerosis.