Primary and Secondary Tumors

Introduction

The first demonstration of a left atrial myxoma by ultrasound occurred in Germany in 1959. Since then echocardiography has evolved to become the usual initial modality for detecting a cardiac tumor. Cardiac neoplasms are found in only 1%–2% of cases in general autopsy series. For this reason, routine screening to rule out cancer in the heart is not appropriate and would undoubtedly lead to many false positives. This is generally true even in cancer patients, in whom there is higher risk (autopsy incidence reported in up to 4%–8%) of cardiac tumors. However, there are exceptional circumstances, such as familial tumor syndromes and carcinoid, in which screening may be justified. Because of the rarity of primary malignancies, the best data available originate from autopsy studies and larger specialized single-center studies, supplemented by case reports in the literature.

A fair proportion of heart tumors are clinically silent and discovered as incidental findings in the process of ancillary testing or workup prior to a surgery. In other cases, systemic embolization or pericardial involvement with hemodynamic effect may be the sentinel event that initiates a cardiac workup. Even more rarely, large masses of the heart may impede cardiac inflow or outflow, cause valvular regurgitation, and hence cause heart failure or syncope.

With knowledge of the general distribution of cardiac tumors and by taking the patient’s age and comorbidities into consideration, along with the location and echocardiographic features of the mass, the clinician can make an educated guess as to the likely nature of the tumor. After the possibilities are narrowed down, one can formulate a diagnostic and therapeutic plan, which may involve further imaging with intravenous (IV) echo contrast, three-dimensional (3D) echocardiography, transesophageal echocardiography (TEE), or other modalities to better define the tumor boundaries and stage before deciding upon observation, surgery, or other treatment. Echocardiography also serves to monitor for growth, recurrence after treatment, or adverse sequelae of tumors.

Tumor Types

Primary Versus Secondary Tumors

The best data for the actual frequency distribution of cardiac tumors are decades old and come from autopsy series, as summarized in Fig. 37.1 . Primary tumors of the heart (see Fig. 37.1A and B ) occur in only 0.02% of autopsy series and represent only 2%–5% of all cardiac tumors. The vast majority are secondary, metastastic neoplasms (see Fig. 37.1C ). Although most clinicians recognize the significance of this binary classification system, the World Health Organization (WHO) has updated and refined their classification and nomenclature in 2015 to better describe rare tumors and those with variable or unknown natural history.

Primary Benign Tumors

Of the primary tumors, approximately 75% are benign, and approximately 30% of these in the general population (up to 50% in adults) are myxomas. The next most common primary tumors are lipomas (10%) and papillary fibroelastomas (8% of general population). Echocardiographic characteristics and patient demographics are often enough to distinguish these three entities. (Of note, the prevalence of tumors reported in the literature from living patients may differ slightly from incidence rates reported from autopsy series, particularly for benign tumors).

Myxoma

Cardiac myxomas are the most common type of primary cardiac tumor, particularly in adults. They are believed to arise from endocardial (mesenchymal) cells. The classic myxoma arises in the left atrium (in 75% of the cases), but 20% of cases arise in the right atrium, and the remaining 5% occur in the ventricles. It is common for the myxoma to be attached to the interatrial septum near the fossa ovalis via a stalk or pedicle, although attachments to the mitral valve have also been described.

On echocardiography, myxomas often appear as compact, gelatinous-appearing masses that can be globular, ovoid, or multilobular ( Fig. 37.2 and Video 37.1 ). However, there exists a spectrum of morphologies. Smaller tumors are often more papillary or villous in appearance, are friable, and are more prone to embolization. In contrast, larger bulky myxomas tend to be more discrete, with a smoother surface or “cluster of grapes” appearance. These can grow large enough to fill the left atrium and are renowned for causing both mitral stenosis, with a diastolic rumble and a tumor “plop” on auscultation, as the mass prolapses into the left ventricle in diastole ( Video 37.2 ). TEE can help determine if the myxoma extends into the pulmonary veins or vena cavae.

There is an autosomal dominant form of myxoma, which constitutes approximately 7% of cases, that tend to present earlier in life (i.e., second decade) than the sporadic myxomas. Individuals affected by this mutation in the PRKAR1A gene (which encodes a regulatory subunit of protein kinase A) or alternatively by a chromosome 2p16 mutation, tend to develop myxomas in atypical locations, even extracardiac locations, with multiple and recurrent sites. The “Carney complex” is a syndrome associated with these mutations that consists of myxomas, hyperpigmented skin spots (lentiginosis), and endocrine overactivity. First-degree relatives of identified patients should be screened by echocardiography, and the patients themselves must be surveyed frequently for recurrence of myxoma.

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