A 44-year-old man with non-exercise-related chest pain was referred to our centre with the suspicion of pulmonary thromboembolism (PT). Transthoracic echocardiography of the aortic root in the short-axis view revealed that the pulmonary trunk was filled with a mass (heterogeneous echo signal), extending from the main pulmonary artery (MPA) to the left and right pulmonary arteries (LPA, RPA) (Panel A1). In addition, an ultrasound scan detected diffuse deep vein thrombosis (Panel A2). Pulmonary computed tomography angiography showed a large hypodense filling defect in the pulmonary arteries (Panel B1 and B2, Supplementary dataSupplementary data online, Video S1). To differentiate between thrombus and tumour, cardiovascular magnetic resonance (CMR) was performed to evaluate the tissue characteristics of the pulmonary mass. Sagittal view of steady-state free precession cine imaging showed that the lesion had unclear boundaries and poor mobility (Supplementary dataSupplementary data online, Video S2). On diffusion weighted imaging, the lesion appeared hyperintense (Panel C1) and the apparent diffusion coefficient value was 0.25 × 10⁻³ mm²/s. Fat-suppressed T2-weighted imaging revealed a heterogeneously hyperintense filling defect with an irregular proximal margin (Panel C2). On contrast-enhanced imaging, the lesion was shown to be heterogeneously enhanced (Panel C3). The tissue characteristics of the pulmonary mass on CMR imaging seemed to fit best with the diagnosis of a pulmonary intimal sarcoma (PIS) and exclude a PT. Subsequently, the patient underwent pulmonary artery resection and reconstruction (Panel D) followed by post-operative chemotherapy. Immunohistochemical analysis results were consistent with PIS (Panel E). The patient has no complaints and is still in remission.

中文翻译：

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肺动脉中的肿块：心脏磁共振的增量值。

一名患有非运动性胸痛的44岁男性因怀疑患有肺血栓栓塞症（PT）而被转诊至我们中心。经主动脉根部的经胸超声心动图在短轴视图中显示，肺干充满了肿块（异质回声信号），从主肺动脉（MPA）延伸至左右肺动脉（LPA，RPA）（面板A1）。此外，超声扫描检测到弥漫性深静脉血栓形成（图A2）。肺部X线断层血管造影显示肺动脉中存在大量低密度充盈缺损（面板B1和B2，在线补充数据，视频S1）。为了区分血栓和肿瘤，进行了心血管磁共振（CMR）以评估肺部肿块的组织特征。稳定状态的进动电影影像的矢状面视图显示，病变边界不清晰，活动性较差（补充数据在线补充数据，视频S2）。在弥散加权成像中，病变表现为高强度（面板C1），表观弥散系数值为0.25×10⁻³ mm ² / s。脂肪抑制的T2加权显像显示异质性高强度充盈缺损，近端边缘不规则（面板C2）。在对比增强成像中，病变显示出异质性增强（图C3）。CMR成像显示的肺部肿块的组织特征似乎最适合诊断肺内膜肉瘤（PIS），但不包括PT。随后，患者接受了肺动脉切除和重建（面板D），然后进行了术后化疗。免疫组织化学分析结果与PIS一致（图E）。该患者没有任何不适，仍在缓解中。