The tumor is composed of large cells with abundant clear vacuolated cytoplasm. The stroma is scanty. Due to the high glyogen content, these cells would be strongly PAS positive.
The swollen myocytes have a centrally placed nucleus with strands of cytoplasm reaching toward the periphery of the cell -- the so-called spider cell
Cardiac rhabdomyoma is the most common benign congenital cardiac neoplasm. An intracardiac mass seen in an infant is most likely a rhabdomyoma. The majority of tumors are multiple with the ventricles being most frequently involved. Involvement of the atria range from 3% to 30% (Fletcher).
Rhabdomyomas are associated with the TSC1 and TSC2 genes, affecting more than 50% of patients with tuberous sclerosis. Conversely,a study of 33 infants and children 30 (90.9%) had associated tuberous sclerosis (Bosi).
Grossly, the tumor is circumscribed with a waxy consistency and range from a few millimeters to several centimeters. Occasionally, the tumor may be so large as to obliterate the entire cavity. Histologically, there is a proliferation of swollen myocytes with clear, glycogen-containing cytoplasm with a centrally placed nucleus. Strands of cytoplasm extend to the periphery of the cell, thus, eliciting the descriptive term "spider cell" for these myocytes. Striations can often be seen in the eosinophilic strands, and the stroma surrounding the tumor cells is sparse (Fletcher).
The tumor demonstrates positivity for normal heart muscle markers such as myoglobin, actin, desmin and vimentin.
The clinical presentation varies and ranges from stilbirth and perinatal death to a largely asymptomatic picture. In other patients, the tumor may cause heart failure due to outflow obstruction, arrhythmias, and thromboembolic disease. Rare instances of myocardial infarction in utero and sudden death have been reported (Fletcher). The left ventricle is the preferential site in the heart, although it any chamber may be involved.
Spontaneous regression is the rule, so if a diagnosis of rhabdomyoma is made, no treatment is necessary unless the lesion is causing a life-threatening condition.
→Most common heart tumor in children is rhabdomyoma and most common heart tumor in adults is myxoma.
→The characteristic cell is the so-called spider cell.
→Strong association with tuberous sclerosis.
→Spontaneous regression occurs in the majority of cases.
Bosi G, Lintermans JP, Pellegrino PA, et al. (1996) The natural history of cardiac rhabdomyoma with and without tuberous sclerosis. Acta Pediatr 85:928–931.
Fletcher CDM, ed. Diagnostic Histopathology of Tumors. 3rd Ed. Philadelphia, PA: Elsevier; 2007: 17-9.