A 52-Year-Old Lady with a History of Locally Advanced Breast

A 52-year-old lady with a history of locally advanced breast cancer visits the office for follow-up. The patient has not received radiation therapy but is getting chemotherapy with trastuzumab as the main ingredient. She doesn't have any symptoms other than a little weariness. The heart rate is regular at 85 beats per minute and blood pressure is 120/72 mm Hg. The patient is afebrile. A 40% left ventricular ejection fraction is seen on transthoracic echocardiography, with no signs of valvular disease. Prior to the start of chemotherapy, a cardiac evaluation was performed and found to be normal. Which of the following pathologic findings is most likely to be present in this patient's heart?

A) Abnormal protein accumulation in the extracellular space
B) Focal ischemic cardiomyocyte necrosis
C) Myocardial tumor cell infiltration
D) Patchy cardiomyocyte necrosis with diffuse myocardial fibrosis
E) Reduced cardiomyocyte contractility with no fibrosis