Description

A woman in her 30s with stage 4 B-Raf proto-oncogene, serine/threonine kinase (BRAF) mutant melanoma with known pulmonary, intraorbital, brain and subcutaneous metastases was found to have a large mass in the right atrium (RA) on staging CT. This was new compared with a previous CT (figure 1A,B). The patient was asymptomatic from a cardiac perspective. There were no features of cardiac failure detected on examination.

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Figure 1

(A) CT imaging at baseline. (B) Right atrium (RA) mass on CT imaging measuring 40 mm. (C) Transthoracic echocardiogram (TTE) image demonstrating the RA mass originating from the tricuspid leaflet. (D) Cardiac magnetic resonance (CMR) showing high T1. (E) Mass was isointense on T1-weighted CMR images. (F) High T2 short tau inversion recovery (STIR) signal. (G) Contrast up-take demonstrated on first pass perfusion on CMR images. (H) Heterogeneous enhancement in the late phase following contrast. (I,J) CT and TTE images, respectively, showing resolution of the intracardiac mass following targeted therapy.

Transthoracic echocardiogram (TTE, figure 1C) subsequently demonstrated a pedunculated, mobile RA mass. The mass originated from the anterior tricuspid leaflet, measuring up to 45 mm and obstructing right ventricle inflow (peak gradient 9 mmHg). Cardiac magnetic resonance (CMR) showed the mass had a high T1 (1600 ms, figure 1D), was isointense on T1-weighted images (figure 1E), high T2 short tau inversion recovery (STIR) signal (figure 1F) and took up contrast on first pass perfusion (figure 1G). There was heterogeneous enhancement in the late phase following contrast (figure 1H).

Following a multidisciplinary meeting between the oncology, cardiology and cardiothoracic surgical teams, the decision was made for systemic immunotherapy as opposed to surgical intervention due to the high tumour burden and multiorgan involvement. Ipilimumab and nivolumab were started as first-line therapy. Due to further disease progression, second-line treatment with combination targeted therapy encorafenib (BRAF inhibitor) and binimetinib (mitogen-activated protein kinase inhibitor) was commenced. Early CT and TTE imaging following targeted therapy demonstrated almost complete resolution of the mass (figure 1I,J). Follow-up CMR was not performed, which is a limitation in the comparison of imaging pre and post therapy.

Cardiac metastasis of malignant melanoma can be intramyocardial, endocardial or pericardial.1 2 They are difficult to detect at an early stage with CT imaging and patients are often asymptomatic.3 Multimodality imaging with CMR, in particular, is useful for tissue characterisation. The T1 of the tumour is determined by the melanin content (decreasing T1 with increasing melanin). T2-weighted images are typically hyperintense and there is contrast uptake due to the vascular nature of the tumour.