A 20-year-old female patient had a 3-month history of progressive dyspnea. Physical examination showed isolated lentigines of the lower lip, palms of both hands, and left flank. Cardiovascular findings revealed a holosystolic heart murmur at the lower left sterna border. The electrocardiogram was in sinus rhythm with an incomplete right bundle branch block (Figure 1). Transesophageal echocardiogram revealed a right ventricular (RV) hypodense mass of 80 x 57 mm extending through all the RV toward the tricuspid valve with RV outflow tract obstruction and a smaller left ventricular (LV) apical mass of 10 x 10 mm. Severe mitral and tricuspid regurgitation were noted. The initial N-terminal pro b-type natriuretic peptide was 1,465 pg/ml. A contrast computed tomography scan was made, reporting a 22 HU mass in the RV of 50 x 48 x 71 mm that extended to the tricuspid valve; in the apical segment of the LV there was a similar mass of 14 x 15.5 x 12 mm (Figures 2-3).
The patient was taken to elective surgery, and the masses were resected and both mitral and tricuspid valves were replaced with bioprostheses (Figure 4). Histopathology confirmed a fragmented myxoma with a hyalinized pedicle without residual endocardial lesions (Figure 5). The complete hormonal panel was normal. Her family was studied. Both of her siblings had ephelides and lentigines; however, there was no evidence of cardiac tumors in any of her relatives. In 2016, the patient had a normal pregnancy with a cesarean section and no complications. Eight months later, a transthoracic echocardiography study showed no residual masses. During her follow-up in 2017, nodular lesions were found in her left breast. A breast ultrasound was revealed multiple nodules, with characteristics of myxomas versus myxoid fibroadenomas.
What is this patient's most likely diagnosis?