Undifferentiated Cardiac Sarcoma on the Mitral Valve Mimicking Myxoma

A 53-year-old male presented with progressive fatigue and dyspnea for 2 months. On admission, echocardiography revealed a leaf-shape mass anchored to the mitral valve (Figure A), which was causing moderate mitral stenosis with an effective orifice area of 1.5 cm² and forward blood flow acceleration with V_max =2.3 m/s (Figure B). Cardiac magnetic resonance confirmed the mass and found that it moved with the opening and closing of the mitral valve (Figure C). The mass measured as 3.1×2.4 cm and showed intermediate T1 signal, high T2 signal, and heterogeneous late gadolinium enhancement (Figure D). Myxoma, a benign tumor, was initially suspected. However, single-photon emission computed tomography (PET-CT) scan demonstrated increased glucose metabolism of the mass and strongly suggested malignancy (Figure E). Therefore, the patient underwent concurrent mass resection and mitral valve replacement. Hematoxylin-eosin staining revealed obvious atypia and mitotic figures, a mixture of round, fat spindle, and pleomorphic tumor cells (Figure F). Immunohistochemistry staining was positive SMA (Figure G) and CDK (Figure H), whereas CD34, S-100, and MDM2 yielded negative results. This suggested the diagnosis of primary cardiac undifferentiated sarcoma. Chemotherapy was initiated and cranial radiotherapy was added 1 year later due to metastasis to the right temporal lobe (Figure I).

Figure.

Transthoracic echocardiogram showing a leaf-shaped mass anchored to the mitral valve (arrow, A). Color Doppler imaging shows moderate mitral stenosis with an effective orifice area of 1.5 cm² and forward blood flow acceleration with a V_max of 2.3 m/s (B). Cardiac magnetic resonance imaging shows the mass with heterogeneous late gadolinium enhancement (C,D, arrows) and PET-CT scan show increased glucose metabolism of the mass (E). Hematoxylin and eosin staining (×200) shows obvious atypia and mitotic figures and a mixture of round, fat spindle, and pleomorphic tumor cells (F). Immunohistochemical staining (×200) positive for SMA and CDK (G,H). Right temporal lobe metastasis detected 1 year after cardiac surgery (I).

Undifferentiated sarcoma originating from the mitral valve is extremely rare.¹ As in the present report, a mass without obvious signs of invasiveness or pericardial effusion may resemble a benign tumor. Thus, PET-CT scan and biopsy further help to identify the nature of masses on the mitral valve.

Acknowledgments

This work was supported by the 1·3·5 Project for Disciplines of Excellence, West China Hospital [grant no. ZYJC18013]; the National Natural Science Foundation of China [82000353], and the China Postdoctoral Science Foundation (2019M663523).

Disclosures

All authors report no conflicts of interest or disclosures.

Ethics Committee

West China Hospital [2016(335)].

Reference

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