Recurrent arrhythmic syncope caused by giant interventricular septum desmoid tumour

Summary

A 27-year-old woman was admitted due to recurrent palpitation and four episodes of syncope. Electrocardiogram during palpitation showed sustained mono-morphic ventricular tachycardia (see Supplementary data online, Data S1). Physical examination revealed a subtle systolic murmur. Transthoracic echocardiography demonstrated a large akinetic heterogeneous mass (4.5 × 5.3 cm) in the interventricular septum (Panel A), two-thirds of which was occupied by the lesion illustrated by contrast-enhance computed tomography (CT) (Panel B). Magnetic resonance imaging showed non-uniform enhancement of the mass (Panel C), corresponding to areas of high cellularity and hypocellular collagen. Positron emission tomography/CT showed only mild fluorodeoxyglucose uptake (SUVmax 4.0) (Panel D), suggesting low-grade malignancy. At surgery, a white firm, non-encapsulated mass was visualized in the interventricular septum (Panels E and F; Supplementary data online, Data S2). All grossly visible tumour tissue was resected, and the ventricular septum was repaired and reinforced with a Dacron patch, leaving no residual shunt. Histologic examination showed proliferation of fibroblasts and spindle cell infiltration (Panel G). Nuclear β-catenin staining was positive (Panel H), consistent with desmoid tumour. Masson’s trichrome stain exhibited interdigitating islands of entrapped myocardium scattered between the fibrous tissue (Panel I), which was the potential substrate for re-entrant tachyarrhythmias. The patient was discharged uneventfully. Neither episodic syncope nor tumour recurred during the 26-month follow-up (see Supplementary data online, Data S3 and S4).