AJR Teaching File: Right Ventricular Mass Presenting with a Heart Murmur

Abstract

Case History A 61-year-old woman has had hypertension for 5 years. At a routine follow-up visit, a new cardiac murmur is identified. Cardiac sonography shows a mass in the right ventricle, and the patient is sent for cardiac MRI for further characterization. Radiologic Description The images show a mass involving the right ventricular free wall just distal to the tricuspid valve (Fig. 1A). On the double inversion recovery images, the mass has smooth margins and relatively homogeneous intermediate signal intensity centrally and slightly higher signal intensity peripherally (Figs. 1B-1D). The signal intensity is lower than that of fat but slightly higher than that of myocardium. There is no pedunculation into the ventricular cavity. The pericardium is not visible adjacent to the mass but can be identified adjacent to the right ventricular wall. No pericardial effusion is seen. Differential Diagnosis The differential diagnosis of cardiac masses includes thrombus as well as inflammatory and neoplastic entities. Inflammatory masses include abscesses from tuberculosis and from various bacteria, fungi, and parasites. Tumors of the heart include myxomas, lipomas, teratomas, ectopic thyroid, metastases, and sarcomas. Diagnosis The final pathologic diagnosis in this patient is ectopic thyroid tissue involving the heart (struma cordis). No involvement of the interventricular septum was found. Commentary Ectopic thyroid tissue may occur in any location along an axis from the base of the tongue to the diaphragm. During the third embryologic week, the thyroid begins to develop from a diverticulum of the foramen cecum in the region of the primitive craniofacial primordium [1]. This endodermal thyroid primordium is tubular until the sixth embryologic week, after which it becomes solid. At this time, under normal circumstances the distal end divides into two lobes and becomes the primitive thyroid gland [2]. The cephalad end is in contact with tissue that subsequently becomes the lower face and base of the tongue. The caudal end of the tube is in close proximity to the bulbous cordis that subsequently develops into the heart. Failure of these tissues to separate normally results in small islands of thyroid tissue remaining in the developing structures. Ectopic tissue is most commonly found at the base of the tongue followed, in descending order, by the submandibular region, cervical lymph nodes, larynx, trachea, esophagus, mediastinum, diaphragm, and heart [3]. Ninety-one percent of patients with ectopic thyroid of the heart have involvement of the right heart; only two patients have been reported with left heart involvement [1, 4]. The mass usually involves the interventricular septum but may extend to the free wall at or near the base of the heart [2].