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Taylor A. Johnson
February is Heart Month, wherein various organizations such as the American Heart Association and the National Institute of Health raise heart health awareness and promote practices that can lower heart disease or cardiovascular disease (CVD) development. CVD and cancer are unfortunately two of the primary causes of death worldwide. Although CVD and cancer may seem completely unrelated, there are multiple areas in which they do overlap. Here at OncoBites, we have previously discussed the importance of the vascular system with delivering cancer therapies, therapies that impact heart function, and connections between obesity and cancer development. As we close the month of February, this article will discuss tumors that can develop within the heart.
Tumors that develop in the soft, mucus-like connective tissue of the heart called myxomas (from “myxoid,” which refers to a mucus-like substance), are the most common cardiac tumors and are especially prevalent in women. The majority of cardiac tumors are benign, with myxomas comprising at least half of all benign tumors. These tumors may develop on the chamber walls or the valves that separate the chambers. Although myxomas can develop in any cardiac chamber (1), the most common site is the left atrium (2), the chamber responsible for carrying reoxygenated blood from the lungs into the heart for subsequent systemic circulation (Figure 1). The key to treating developing myxomas is to perform surgery promptly upon diagnosis in order to prevent additional complications (early surgery will be a common theme as we discuss other cardio cancers). Fortunately, the surgical outcomes are positive, with a twenty-year survival rate of approximately 85% (3).
Common cardiac tumors that develop in pediatric cases are rhabdomyomas and fibromas. Rhabdomyomas are defined as benign tumors located within striated muscle (i.e. cardiac muscle), whereas fibromas are tumors that develop within connective or fibrous tissues. Tzani et al recently reviewed roughly thirty different clinical studies consisting of approximately 750 pediatric patients (4). Of the tumors found in children & adolescents, approximately eighty-three percent of the tumors identified were benign. The most prevalent benign tumors were rhabdomyomas (over fifty percent), followed with fibromas and myxomas (approximately twenty-two percent each). In comparison, majority of the malignant tumors documented were sarcomas; tumors that develop in soft, connective tissue (4).
Several genetic conditions have been linked to the development of cardiac tumors. Many highly heritable conditions, including Tuberous sclerosis, Carney Complex syndrome, and Gorlin syndrome are caused by mutations of tumor suppressor genes (5). Tuberous sclerosis patients in particular have nearly a 50% chance of developing rhabdomyomas (6). Most patients will undergo echocardiograms for diagnosis and follow up with surgery to remove the cancer (whether it be a fibroma, myxomas or paraganglioma (tumor derived from neural crest cells)). Tuberous sclerosis patients, however, are an exception, as cardiac rhabdomyomas typically regress by six years of age (5).
As terrifying as the thought of developing cancer is, developing cancer within the heart sounds even more terrifying. Fortunately, the statistical chance of developing a cardiac myxoma is literally a million to one chance. Regarding pediatric tumors, primary cardiac tumors are extremely rare (less than one tenth of one percent). This rarity poses a double-edged sword: the chances of developing cardiac tumors are much smaller compared to other types of tumors, but the rarity of cardiac tumors results in diagnostic and scientific challenges. For example, women are more likely to develop cardiac tumors than in men; however, the scientific reasoning for this is currently unknown, and resources are often diverted to more common cancers. In addition, much of the knowledge of cardiac tumors is based off of case reports or autopsies, rather than basic biomedical science research, which can better answer questions such as 1) why cardiac cancers are so rare and 2) what molecular similarities/differences are present between cardiac and non-cardiac cancers. Hopefully with continued awareness and advancements in imaging techniques (i.e. echocardiography, CTs, MRIs), cardiac tumors will be more readily identifiable and better understood on a molecular, cellular, and physiological basis.
1 – Boutayeb A, Mahfoudi L, and Moughil S. Atrial Myxoma: From Diagnosis to Management. Clin Surg. 2017; 2:1498.
2 – McAllister HA, Hall RJ, and Cooley DA. Tumors of the heart and pericardium. Curr Probl Cardiol. 1999; 24(2): 57-116.
3 – Dell’Amore A, Asadi N, Caroli G, et al. Recurrent primary cardiac osteosarcoma: a case report and literature review. Gen Thorac Cardiovasc Surg. 2014; 62(3): 175-80.
4 – Tzani A, Doulamis IP, Mylonas KS, et al. Cardiac Tumors in Pediatric Patients: A Systematic Review. World J Pediatr Congenit Heart Surg. 2017; 8(5): 624-32.
5 – Lee E, Mahani MG, Lu JC et al. Primary cardiac tumors associated with genetic syndromes: a comprehensive review. Pediatr Radiol. 2018; 48(2): 156-64.
6 – Watson GH. Cardiac rhabdomyomas in tuberous sclerosis. Ann NY Acad Sci. 1991; 615:50-7.