A 22-year-old woman comes to the office due to worsening dyspnea. The patient has also experienced low-grade fevers, a 6.8-kg (15-lb) weight loss, and syncopal episodes over the last 3 months. Her shortness of breath worsens when sitting and improves when lying down. Medical history is insignificant. The patient does not use tobacco, alcohol, or illicit drugs. Temperature is 37.4 C (99.3 F), blood pressure is 115/72 mm Hg, pulse is 75/min and regular, and respirations are 12/min. The lungs are clear. Cardiac auscultation reveals a low-pitched, mid-diastolic rumble at the cardiac apex. The remainder of the physical examination is normal. ECG reveals left atrial enlargement, and echocardiography shows a large, pedunculated mass in the left atrium. Histologic analysis of this mass will most likely reveal which of the following?

Question

A 22-year-old woman comes to the office due to worsening dyspnea.  The patient has also experienced low-grade fevers, a 6.8-kg (15-lb) weight loss, and syncopal episodes over the last 3 months.  Her shortness of breath worsens when sitting and improves when lying down.  Medical history is insignificant.  The patient does not use tobacco, alcohol, or illicit drugs.  Temperature is 37.4 C (99.3 F), blood pressure is 115/72 mm Hg, pulse is 75/min and regular, and respirations are 12/min.  The lungs are clear.  Cardiac auscultation reveals a low-pitched, mid-diastolic rumble at the cardiac apex.  The remainder of the physical examination is normal.  ECG reveals left atrial enlargement, and echocardiography shows a large, pedunculated mass in the left atrium.  Histologic analysis of this mass will most likely reveal which of the following?

Quizplus · Accepted Answer

11ec160b_38c1_826d_9249_d9c06a8b888b_MD0001_00 This patient with a large, pedunculated mass in the left atrium most likely has an atrial myxoma. Myxomas are the most common primary cardiac neoplasm, and approximately 80% arise within the left atrium. Left atrial myxomas frequently obstruct blood flow from the left atrium to the left ventricle, leading to a murmur mimicking that of mitral stenosis (ie, mid-diastolic rumble at the apex). The obstruction can also lead to a decrease in cardiac output that manifests as dyspnea, lightheadedness, or syncope. Because the mass is typically mobile, obstructive symptoms may be transient and influenced by position (ie, upright posture exacerbates mitral obstruction, whereas lying down alleviates it). In some patients, fragments of the mass may embolize into the systemic circulation (eg, resulting in stroke or acute limb ischemia). In addition, some myxomas can produce cytokines (eg, interleukin-6) that lead to constitutional symptoms including fever and weight loss. Histologically, these tumors demonstrate scattered myxoma cells within a mucopolysaccharide stroma and blood vessels, which may be encircled by myxoma cells. Myxomas produce a large amount of vascular endothelial growth factor, which contributes to the angiogenesis, hemorrhaging (seen as brown hemosiderin deposits), and friability characterizing these tumors. (Choices A and B) Coarse, filamented, branching septate hyphae are found in fungal endocarditis, whereas gram-positive cocci in clusters are consistent with bacterial endocarditis. Both are unlikely in this young woman with no history of valvular disease or intravenous drug use. In addition, endocarditis typically causes a regurgitant murmur, with valvular vegetations seen on echocardiography. (Choice C) Acute myeloid leukemia (AML) rarely may involve the heart. Signs and symptoms related to anemia (eg, weakness, fatigue), neutropenia (eg, infections), and thrombocytopenia (eg, ecchymoses, epistaxis), are typically present with AML. (Choice E) Nonbacterial thrombotic endocarditis involves the valvular deposition of sterile platelets and fibrin and most commonly occurs in the setting of advanced malignancy or systemic lupus erythematosus. The disease usually presents with systemic embolization, and heart murmurs are often absent; if a murmur is present, it is typically regurgitant rather than stenotic. Educational objective: Myxomas are the most common primary cardiac neoplasm and usually arise within the left atrium. The tumors typically cause position-dependent obstruction of the mitral valve, leading to a mid-diastolic murmur and symptoms of decreased cardiac output (eg, dyspnea, syncope). Constitutional symptoms (eg, fever, weight loss) may also be present. Histologically, the tumors demonstrate scattered cells within a mucopolysaccharide stroma and blood vessels with hemorrhage.

A 22-Year-Old Woman Comes to the Office Due to Worsening