A stenotic valve is removed from a 70-year-old man. The value demonstrates hard nodular masses heaped up within the sinuses of Valsalva. On microscopic section, the acellular masses stain darkly blue with hematoxylin and eosin. Which of the following is the MOST significant constituent of the masses?

The valvular disease is calcific aoic stenosis, a disease of the elderly in which nodules of calcium salts, notably calcium phosphate salts, form as a result of dystrophic calcification. Dystrophic calcification can also be seen at sites of previous necrosis of many etiologies (coagulative, caseous, liquefactive, or enzymatic fat necrosis) and in advanced atherosclerosis.Calcium oxalates are found in some kidney stones.Complexed iron is seen in hemosiderin deposits, often at sites where there has been previous hemorrhage or if there is a systemic overload of iron.Magnesium phosphates are found in some kidney stones. Ref: Taylor R.D., Asinger R.W. (2009). Chapter 29. Long-Term Anticoagulation for Cardiac Conditions. In M.H. Crawford (Ed), CURRENT Diagnosis & Treatment: Cardiology, 3e.