Microenvironment in Cardiac Tumor Development: What Lies Beyond the Event Horizon?

Cardiac tumors are found in less than 1% of adult and pediatric autopsies. More than three-fourths of primary cardiac neoplasms are benign, with myxomas and rhabdomyomas being the most common cardiac tumors seen in adults and children, respectively. Primary malignant cardiac tumors are extremely rare, whereas metastatic lesions can be seen in approximately 8% of patients dying from cancer. Attempting to understand why the heart is so resistant to carcinogenesis and which fail-safe mechanisms malfunction when cardiac tumors do develop is particularly challenging considering the rarity of these tumors and the fact that when relevant clinical studies are published, they rarely focus on molecular pathogenesis. Apart from cancer cells, solid tumors are comprised of a concoction of non-cancerous cells, and extracellular matrix constituents, which along with pH and oxygen levels jointly constitute the so-called tumor microenvironment (TME). In the present chapter, we explore mechanisms through which TME may influence cardiac carcinogenesis.