A 73-year-old woman has had episodes of chest pain during the past week. She is afebrile. Her pulse is 80/min, respirations are 16/min, and blood pressure is 110/70 mm Hg. On auscultation of the chest, heart sounds seem distant, but the lung fields are clear. Neck veins are distended to the angle of the jaw, even while sitting. There is a darkly pigmented, irregular, 1.2-cm skin lesion on the right shoulder. A chest radiograph shows prominent borders on the left and right sides of the heart. Pericardiocentesis yields bloody fluid. Laboratory findings include a serum troponin I level of 0.3 ng/mL. Which of the following lesions is the most likely cause of these findings?

**Core Concept**
The patient's symptoms and laboratory findings suggest a diagnosis of cardiac tamponade, a condition characterized by fluid accumulation in the pericardial sac leading to impaired cardiac filling and reduced cardiac output. The presence of a pericardial effusion with bloody fluid and distant heart sounds on auscultation supports this diagnosis.

**Why the Correct Answer is Right**
The patient's presentation is consistent with a pericardial effusion, which is confirmed by the chest radiograph showing prominent borders on the left and right sides of the heart. The bloody fluid obtained during pericardiocentesis is indicative of a hemorrhagic pericardial effusion, which is often secondary to a malignancy. The presence of a darkly pigmented, irregular skin lesion on the right shoulder suggests a possible diagnosis of melanoma, which is a common malignancy associated with pericardial metastasis. The serum troponin I level of 0.3 ng/mL is within normal limits, indicating that the cardiac damage is not due to a myocardial infarction.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while a myocardial infarction (MI) can cause cardiac tamponade, the serum troponin I level in this patient is within normal limits, making an MI less likely.
**Option B:** This option is incorrect because a pulmonary embolism (PE) typically presents with respiratory distress, hypoxia, and an abnormal chest radiograph, which are not present in this patient.
**Option C:** This option is incorrect because while a myocarditis can cause cardiac tamponade, the patient's presentation and laboratory findings do not suggest an inflammatory process.

**Clinical Pearl / High-Yield Fact**
A pericardial effusion with bloody fluid and distant heart sounds on auscultation should raise suspicion for a malignancy as the underlying cause, particularly if a skin lesion is present.

**Correct Answer:** D. Melanoma.

✓ Correct Answer: C. Epicardial metastases