Undifferentiated high-grade pleomorphic sarcoma of the mediastinum.

An 82-year-old woman presented with chest pain and exertional dyspnea for 1 week. Her medical history was unremarkable, except for controlled hypertension. Electrocardiography revealed ST-segment elevation in most leads (Fig. 1); echocardiography revealed a pericardial effusion collection without any segmental wall motion abnormalities, indicating acute pericarditis. Laboratory findings were not suggestive of infections or autoimmune diseases; her serum tumor marker tests were negative. Contrast-enhanced computed tomography revealed an irregular periaortic mass (Fig. 2A1 and A2). Pericardial and pleural effusion aspirate was both unremarkable. Therefore, mediastinal mass biopsy was performed, suggesting sarcoma not otherwise specified. The tumor deemed unresectable. The patient opted for palliative care and died of right cardiac failure in a month. Autopsy revealed that a white elastic tumor surrounded the aorta and pulmonary artery without protrusion into the vascular cavity and wholly occupied the pericardial cavity with slight infiltration into the myocardium (Fig. 2B1 and B2). According to the 2013 WHO classification, the histological type was compatible with undifferentiated high-grade pleomorphic sarcoma (UHPS) [1].

Figure 1

Electrocardiography revealed ST-segment elevation and PR depression in leads I, II, aVL, aVF and V4–6 and PR elevation in lead aVR.

Figure 2

(A1 and A2) Contrast-enhanced computed tomography on coronal view revealed an irregular periaortic mass (red asterisk in A1) and thickening of the ascending aortic wall and pericardium continuous from the mass; (B1 and B2) autopsy revealed that a white elastic tumor surrounded the aorta and pulmonary artery without protrusion into the vascular cavity and wholly occupied the pericardial cavity. Ao: Aorta, PA: Pulmonary artery, Tr: Trachea, LV: Left ventricle, RV: Right ventricle.

UHPS, widely known as malignant fibrous histiocytoma, usually occurs in the extremities and retroperitoneum; its incidence in the mediastinum is very low [2]. The prognosis of the mediastinum of UHPS was dismal because surgical resection as the main approach to treatment was often incomplete [3]. In this case, the tumor expanded, surrounding adjacent organs almost without infiltrating into them although UHPS often proliferates into a large mass [4, 5]. This rare extension pattern induced acute pericarditis and made the resection of tumor extremely difficult. Clinicians should note that UHPS may arise from the mediastinum and spread via different routes, leading to an acute fatal outcome.