P126A "MASSquerade"; Not your average cardiac mass

Abstract

A 52 year old lady, with a background of hypertension, presented with troponin negative chest pain. Her electrocardiogram (ECG) was unremarkable; however chest x-ray (a) showed obscuration of the right heart border, in keeping with middle lobe lung pathology. A CT scan of her chest showed a 1.3 by 3.3 by 3cm lobulated lesion which appeared to be arising within the pericardium adjacent to the right atrium. An echo-cardiogram (b) revealed a small mass in the right atrium which was intensely metabolically active on 18F-fluorodeoxyglucose (FDG) PET-CT (c). Cardiac MRI demonstrated a right atrial sessile mass of around 2.9 by 2.2 by 1.5cm attached to the posterior wall of the RA that did not appear to breach tissue planes and did not extend into the superior or inferior vena cava (d-f). Native T1 values of the mass (g) were similar to myocardium (1094ms by MOLLI, myocardial T1 1070ms), and had low signal on T1 weighted fat-water imaging. The mass perfused on resting first pass perfusion imaging and contrast-enhanced on both early and late gadolinium imaging (h,i), suggesting a likely malignant mass with a sarcoma high on the list of differential diagnoses. Surgery was performed for diagnostic and potential treatment purposes. A mass was seen in the right atrium which was hard in consistency with a smooth contour, which was completely excised. Histology demonstrated myocardium which was partly replaced by a diffuse proliferation of lymphocytes, plasma cells and histiocytes associated with fibrosis. Emperipolesis was also noted which extended beyond the myocardium into the pericardium and endocardium. The histiocytes were decorated by CD163 and S100 with a significant proportion of the plasma cells being IgG4 positive. The overall morphology and immunophenotype was most in keeping with a diagnosis of Rosai Dorfman Destombes (RDD) disease. The patient has been well and asymptomatic since the excision of mass, and is being monitored for disease recurrence and the need for systemic chemo/immunotherapy. Cardiac involvement in RDD disease is a rare manifestation of a rare disease, occurring in 0.1-0.2% of cases. Cardiac involvement can be seen in all chambers of the heart, valves, pericardium, aorta, and pulmonary arteries. We have previously reported a case of RDD presenting with cardiac tamponade, where the whole heart, coronary and pulmonary arteries were encased in tumour. This current case highlights a different manifestation of cardiac RDD disease, and suggests the disease should be considered as an uncommon differential diagnosis of cardiac masses. The management of cardiac RDD disease varies depending on the pathophysiology, site of disease, and presence of symptoms. Literature review suggests that surgical excision of intra-cardiac masses confers a good prognosis.