We present the case of a 36-year-old woman with Noonan syndrome and congenital heart disease in whom extragenital endometriosis caused an extraordinarily large jelly-like paracardiac and abdominal mass. Protrusion through an intercostal space caused a pulsating subcutaneous tumor on the left lateral thoracic wall. The patient never complained of menstruation-related pain. Histology obtained during several prior surgical interventions had been inconclusive. Thus definitive diagnosis was delayed for years. A literature review revealed no known association between Noonan syndrome and endometriosis.