I. Imaging examination methods of esophageal cancer
In addition to definite diagnosis, imaging examination should pay special attention to provide information of tumor stage for esophageal cancer patients so as to design reasonable treatment plan and evaluate prognosis.
There are many imaging examinations for esophageal cancer, such as barium meal imaging, CT examination, MR examination and intra-luminal ultrasound examination. Each examination method has its advantages and limitations, for example, barium meal esophagogram can only observe and understand the situation inside the esophageal lumen, but cannot understand whether the tumor has invaded or metastasized; CT and MR examination are good for observing whether the tumor has invaded or metastasized, but cannot show the whole picture of the lesion inside the esophageal lumen well. Barium esophagogram is a simple, economical, practical and effective method to diagnose esophageal tumor.
(1) X-ray examination: esophagogram is one of the easiest and practical methods to diagnose esophageal cancer, special attention should be paid to the following points when examining patients with esophageal cancer.
(1) Pay attention to the modulation of barium agent so that it has good adhesion and mobility.
(2) Dual gas-barium imaging should be done to better show the morphology, contour, scope, mucosa and diastolic degree of the lesion, which is an essential step for patients suspected of early stage cancer.
(3) A detailed chest fluoroscopy should be performed to observe whether there are metastases or other diseases in the lungs and mediastinum, the size of gastric alveoli, and whether there are soft tissue masses in them.
(4) The best time and film must be selected to show the lesion. In addition to left and right anterior oblique spot films of the local lesion, lateral films should be taken of the cervical esophagus to show its relationship with the trachea. In addition, the entire length of the esophagus, including the cardia gastric fundus, should be photographed.
(ii) CT scan: It should be taken on an empty stomach. Enhanced scan helps to show the adjacent large blood vessels of the heart and improve the contrast. The patient is usually placed in a supine position and swallowed dilute iodine solution and gas to show the esophageal lumen. Refer to esophagogram film to take a thin scan (2MM – 5MM) or reconstruction at the lesion site to reduce the partial volume effect so that the relationship between the tumor and the surrounding structures can be shown clearly.
(iii) MRI: fasting scan, T1 and T2-weighted images, local thin layer continuous without interval, cross-sectional and sagittal scans can show the relationship between tumor and surrounding tissues, coronal plane helps to observe mediastinal lymph nodes.
(4) Intraluminal ultrasound of esophagus: with 7.5MHz transducer, its spatial resolution can reach 0.2mm and penetration depth can reach 5cm–7cm, which can show all layers of esophageal wall and regional lymph nodes.
Imaging performance of esophageal cancer
(1) Barium esophageal imaging manifestations of early esophageal cancer.
(1) Plaque type: It is also called augmentation type. The mucosa of the lesion is irregularly and slightly swollen and elevated, the surface is rough and granular, the thickness of the mucosa is uneven and can be interrupted, such as the shape of a lying silkworm, or there are small niches with superficial erosion, the local canal wall is slightly stiff, and the expansion is limited or not.
(2) Papillary type: The tumor is nodular, papillary or polyp-like elevation, protruding into the lumen and forming a filling defect, its edge is clearly demarcated from the surrounding mucosa, local mucosa is interrupted, the dilation of the duct wall is poor, and the surface of the tumor is occasionally erosion, resembling orange peel. Larger papillary type early esophageal cancer is sometimes difficult to distinguish from progressive esophageal cancer.
(3) Cicatricial type: It is also called depressed type. The mucosa of the lesion is disrupted, with erosion or superficial ulceration, and the barium meal imaging shows irregular spot-like barium storage area, which may also show dashed line or map-like changes, and in some cases, there may be slight elevation of the mucosa at the edge of the depression. The duct wall diastole is slightly restricted.
(4) Flat type: The cancer is located on the mucosal surface, the mucosa of the lesion is neither elevated nor depressed, and the local mucosa only shows congestion changes. The nature and location of the lesion can often be determined by endoscopic biopsy.
(II) Imaging manifestations of middle and advanced esophageal cancer
1.Barium meal esophagogram
(1) Medullary type: The lesion is longer in extent and invades the whole circumference of esophagus, with irregular filling defect, thickened and rigid esophageal wall, and mucosal destruction, and barium meal imaging shows ulcers and nodular bulges of different depths and sizes. The lumen is narrowed, and the barium flow is poor or obstructed. The migration between the lesion and normal esophagus is sloping, and the lumen travels twisted into an angle if the tumor invasion is obvious.
(2) Mycosis fungoides type: The lesion is often limited to part of the canal wall, with flattened myxoid filling defect, protruding into the canal lumen, the surface may be smooth, but most of them are swellings with ulceration or erosion on the surface in line with the long axis of the esophagus, with neat edges, clear migration zone with normal esophagus, and local mucosal destruction. The esophageal wall on the opposite side of the lesion may be regularly soft.
(3) Ulcer type: The lesion often invades only part of the canal wall, forming an ulcer with irregular edges and uneven bottom, and the bottom of the ulcer often reaches deep into the muscular layer or penetrates the muscular layer. Barium esophagogram shows a deeper niche with slightly elevated edges, and luminal narrowing may not be obvious.
(4) Narrowing type: The lesion involves the whole circumference of the esophagus, the lumen is ring-shaped or funnel-shaped narrowed, the scope is short, usually less than 5 CM. The tumor is clearly demarcated from the normal esophagus. The mucosa of the lesion is flat, and the proximal esophagus is obviously dilated.
(5) Intraluminal type: Large polyp-like filling defect in the lumen is seen at the lesion and infiltrates the esophageal wall, and there is patchy barium residue on the tumor surface due to erosion or shallow ulcer, and the local lumen is widened and expanded. The obstruction of barium flow is not obvious.
2.CT scan examination
(1) Growth of tumor inside and outside the lumen: CT cross-sectional image can observe irregular thickening of esophageal wall caused by tumor, the mass can grow inside or outside the lumen, can grow all around or eccentrically, and the lumen of esophagus becomes small and irregular under pressure, eccentric to one side or completely occluded. Whether the fatty gap between the tumor and the surrounding mediastinal tissues and organs is clear can indicate whether the tumor is invasive or not.
(2) Tracheobronchial invasion: Obvious pressure on trachea or bronchus causing morphological changes or posterior wall irregularity indicates tracheal or bronchial invasion.
(3) Invasion of the aorta: If the fatty gap between the tumor and the aorta disappears, the contact surface is >90°, and the lumen of the aorta is partially flattened, it may suggest that the aorta may be invaded; if the fatty gap between the tumor and the aorta exists, the contact surface is <45°, it suggests that the aorta may not be invaded.
(4) Invasion of the pericardium: The disappearance of the normal fat gap between the tumor and the adjacent part of the heart and the depression and deformation of the heart cavity suggest invasion.
(5) Mediastinal lymph node metastasis: CT scan can help to detect the lymph node metastasis around the lesion and in the mediastinum.
(6) Abdominal lymph node metastasis.
3MRI examination
The diagnostic index of MRI for esophageal cancer and invasion of mediastinum is similar to that of CT, and it shows the fatty interstices around the esophagus more clearly than CT. The tumor shows medium signal in T1-weighted image and medium-high signal in T2-weighted image.
4.Esophageal luminal ultrasound examination
Intraluminal ultrasound examination of esophagus can observe whether the normal five-layer structure of esophageal wall is destroyed by tumor, the invasion of tumor and regional lymph node metastasis.
(3) Differential diagnosis of esophageal cancer
1.Other malignant tumors of esophagus
Other malignant tumors of esophagus are very rare, including smooth muscle sarcoma, fibrosarcoma, carcinosarcoma, malignant melanoma, esophageal metastasis, etc.
(1) Esophageal smooth muscle sarcoma: Esophageal smooth muscle tumors occur in the muscular layer, mostly large soft tissue masses, which can grow into the lumen or inside or outside the lumen, often accompanied by central ulcers. CT or MR scan clearly shows the mass growing outside the lumen.
(2) Esophageal carcinosarcoma: Most of the masses with tips protrude into the lumen of the esophagus to form irregular filling defects, and the imaging performance is very similar to that of intraluminal esophageal cancer.
(3) Malignant melanoma: primary malignant melanoma of esophagus is rare, the tumor is brownish black or brownish yellow, the tumor is polyp-like and protrudes into the lumen, it may be lobulated and tipped, the imaging performance is similar to intra-luminal esophageal cancer, but the tumor is often multi-lobulated.
(4) Esophageal metastases: metastases from hematogenous dissemination to esophagus are rare. The primary tumor can be kidney cancer, thyroid cancer, breast cancer, lung cancer and so on. Their esophagogram findings are similar to those of intraluminal esophageal cancer.
2.Benign esophageal tumors and tumor-like lesions
Benign esophageal tumors and aneurysmal lesions account for about 20% of esophageal tumors, of which 50%-70% are smooth muscle tumors. There may also be papilloma, adenoma, polyp, lipoma, hemangioma, cyst, etc.
Esophageal smooth muscle tumors are composed of interlocking smooth muscle and fibrous tissue with a neat envelope, and can be solitary round, oval or multinodular. It is mainly a wall lesion, but it can also grow outside the lumen. Barium esophagogram shows a round or oval shaped mural mass of variable size, with eccentric luminal narrowing, smooth and sharp edges, and a localized widening of the esophagus in frontal view. The surface mucosa is flattened or bifurcated, and the adjacent mucosa is pushed.
3.Benign esophageal lesions
(1) Peptic esophagitis: Barium esophagogram shows spasmodic contraction of the lower esophagus, thickening or blurring of the mucosa, and small barium storage areas or niches when there is erosion or small ulcers. In late fibrosis of inflammatory lesions, there may be luminal narrowing with smooth or serrated edges, but the esophagus still has a certain degree of diastolicity, and the morphology of the lesion is somewhat changed, and the migrating zone between the lesion and normal esophagus is not clear.
(2) Cardia achalasia: A few infiltrating carcinomas of the lower esophagus should be differentiated from it. The stenotic segment of cardia is symmetrical stenosis on both sides of the antral segment of the gastroesophagus with smooth funnel-shaped or bird’s beak-shaped walls, and the obstructive symptoms can be relieved by antispasmodics.
(3) Esophageal varices: manifested as polyp-like filling defect, the mucosa of severe lesions is thickened in the shape of earthworms or beads, but the esophageal wall is soft and has certain contraction or dilation function without signs of obstruction, the filling defect caused by varices has certain changes in different observation time phases. The patient has a history of cirrhosis without symptoms of dysphagia.
(4) External pressure changes: Mediastinal enlarged lymph nodes, large vascular lesions or variants and other intra-mediastinal lesions can cause compression stenosis of the esophagus, which usually has smooth edges and local mucosal spreading without destruction, and CT or MRI examination can help to diagnose.