CHM is a rare disease of mediastinal benign lesion originating from vascular endothelial cells which is caused by abnormal vascular development during embryonic period and composed of masses with varying sizes and dilated cavernous sinus pathologically. The inner wall is lined with vascular endothelium, and the blood sinus cavity is congestive or filled with some phleboliths (calcified thrombosis) [
1]. Eighteen cases in this group (18/19) were solitary lesions, and few multiple cases were reported in the previous studies, which may be the characteristic of this disease. The literature reports that the average age of CHM is about 35 years old [
2,
3]. Most of the patients in this group were middle- and old-aged patients over 50 years old, which may be related to the non-specific clinical symptoms and delayed treatment. Reports showed that there was no significant gender difference in CHM patients, and the proportion of female patients in this group was about 68.4% (13/19), which was different from previous reports that may be related to the statistical bias of small sample size [
1,
2,
4]. Most patients with CHM lack specific clinical manifestations [
2], mainly related to the locations, sizes, and invasion with adjacent structures of lesions [
1,
4]. In this group, the clinical symptoms of nine patients were chest tightness, chest pain, back pain, and cough, and one case manifested fatigue in both eyes, and they all could be considered as relatively clinical symptoms caused by the lesions which compressed and stimulated adjacent structures. The remaining nine patients had no clinical symptoms of the chest and were diagnosed accidentally during health physical examination.
CHM could occur in any area of the mediastinum. In general, the lesion can occur in any part of the mediastinum, with most of the anterior superior mediastinum (about 70%) and the second in the posterior mediastinum (20%) [
5]. In this group, 12 cases occurred in the anterior mediastinum (12/19), while the remaining 7 cases occurred in the posterior mediastinum, which was similar to previous reports. Most of the CHM patients show clear borders and were oval-shaped or round, but it can also invade neighboring tissues and organs to be unclear with surrounding tissues. In this group, four lesions were unclear with adjacent pleura which may be related to the lesions originating from the intercostal blood vessels, and these lesions were easy to misdiagnose as suspicious malignant lesions before operation in this condition. There was no report about this in the past. Reports showed that the intralesional phlebolith is a characteristic imaging manifestation of CHM, and CT was more likely to find it, but the incidence is low. In previous studies, about 16–18% [
2] phleboliths were visible in CHM. In this group, four cases (4/19) of CT scanning showed small circular phleboliths or nodular calcifications, which was similar to previous reports. In this group, two cases with MRI showed equal signal on T1WI, slightly longer signal on T2WI, and obviously high signal on T2WI fat suppression. Some scholars believe that high signal on T2WI fat suppression may be an important sign of CHM [
6]. Besides, two lesions in this group showed high signal on DWI (
b = 800), which may be a characteristic image of CHM and be of great significance for the diagnosis of CHM. This sign has not been reported in the past and may be related to full sinusoids in pathology, scattered hemorrhage, and diffusing limitation of CHM. Due to the vascular sinus interstitial tissue in CHM, there was obviously hyperplastic and fibrotic smooth muscle tissue and there may be different degrees of thrombosis in the vascular sinus cavity so that the blood flow pattern is variable, which leads to more complicated and changeable enhanced ways [
4,
7]. Most of the CHM (14/19) in this group showed mild uneven enhancements while three cases were moderately enhanced and two cases were obviously unevenly enhanced, which was basically consistent with previous reports [
2]. At the same time, in 14 cases of CHM, clearly intensified nodules were observed in the peripheral or center of the lesions during CT-enhanced scanning. The degree of enhancement was similar to the same layer of the thoracic aorta. As continuously enhanced in the venous phase, the enhancement range was expanded characteristically, which was similar to the progressive feature of hepatic cavernous hemangioma. And the MRI multiphase-enhanced scan of one lesion appeared in the “fast in and slow out” feature more clearly, which can be regarded as a specifically diagnostic basis for CHM and be of great value for the diagnosis and identification of this disease. The enhanced feature has been reported in the past [
8]; however, it is not common to show this sign, which may be related to the time of the enhanced scanning for different researches. In this group, the ulnar vein bolus and dual-phase scanning project (25 s arterial phase and 60 s venous phase after contrast agent injection) was used during the chest CT-enhanced scanning and multiphase was used during MRI-enhanced scanning (25 s, 60 s, 150 s, and 200 s, after contrast agent injection). Previous studies generally used 30-s first phase and 120-s delayed phase scanning project after contrast agent was injected [
9]. In addition, dilated malformed drainage veins connected with the brachiocephalic vein and superior vena cava in the lesions were found after contrast agent was injected in five cases of the anterior mediastinum, which was consistent with the feature found by some scholars [
9,
10]. In this group, blood vessel shadows were found in T1WI of one lesion, yet this phenomenon has not been reported in the past. The discovery of these signs often indicates that the lesions is vascular, providing characteristic imaging features for its diagnosis and differential diagnosis, which can prevent patients from further invasive examination and play an important role in the development of surgical project.