Peripheral Malignant Nerve Sheath Tumour: At the Heart of the Matter

A 51-year-old woman presented with a 2-month history of shortness of breath, generalized malaise, headache, and night sweats. Although there were no cardiovascular risk factors, the patient had a history of Factor V Leiden mutation and previous pulmonary embolus treated with anticoagulation. Transthoracic echocardiography confirmed normal biventricular systolic function with multiple echodense masses attached to the apical walls of the left ventricle (LV) (Fig. 1A; and Video 1 , view video online). Computed tomography of the chest confirmed multiple low-attenuation filling defects within the LV, the largest measuring up to 19 mm in size. Additionally, a right lower lobe lung mass with an enlarged left axillary lymph node measuring 3.5 × 3.7 cm was identified on computed tomography imaging (Fig. 1B and Video 2 , view video online). Cardiac magnetic resonance cine imaging confirmed multiple intracardiac masses within the interventricular septum and lateral wall of the LV (Fig. 1C, Video 3 , view video online); these intracardiac lesions were hyperintense to the LV myocardium on both T2 turbo spin echo and fat saturation cardiac magnetic resonance sequences, respectively (Fig. 1, D and E). After the administration of gadolinium, there was enhancement of the intracardiac masses on delayed enhancement imaging, suggestive of malignancy (Fig. 1F). An 18F-fluorodeoxyglucose positron emission tomography scan confirmed intense metabolic activity within the lung, left axilla, and LV (Fig. 1G). Histologic analysis of a core biopsy obtained from the left axilla confirmed a high-grade spindle cell sarcoma on hematoxylin–eosin staining (Fig. 1H) with complete H3 K27me3 loss on immunohistochemistry (Fig. 1I), consistent with a malignant peripheral nerve sheath tumour (MPNST) originating from the brachial plexus. Given the extensive metastasis of the MPNST from the axilla to the lungs, heart, and brain, the patient was treated with whole brain radiotherapy followed by palliative chemotherapy with doxorubicin.