Lung cancer cases present a variety of clinical symptoms and X-ray signs depending on the tumor site, pathological type and early and late stages of the disease, and are easily confused with other lung diseases. Therefore, the differential diagnosis of lung cancer, especially for early stage cases, is important for early diagnosis and treatment.
(A) Tuberculosis
1.Tuberculosis bulb Easily confused with peripheral type lung cancer. Tuberculosis bulbs are mostly seen in young patients. The lesions are often located in the apical and posterior segments of the upper lobe or the dorsal segment of the lower lobe, usually with insignificant growth and a long duration of disease. On X-ray, the density of the mass shadow is not uniform and sparse translucent areas can be seen, often with calcified dots, smooth margins and clear demarcation.
2. The x-ray signs of cornified pulmonary tuberculosis are similar to those of diffuse bronchoalveolar carcinoma. The fever, night sweats and other symptoms of systemic toxicity are obvious, and anti-tuberculosis drug treatment can improve the symptoms and the lesions are gradually absorbed.
3.Pulmonary hilar lymph node tuberculosis The hilar mass shadow on X-ray may be misdiagnosed as central type lung cancer. Tuberculosis of hilar lymph nodes is mostly seen in young and young adults, often with symptoms of tuberculosis infection, rarely with hemoptysis, often with positive tuberculin test, and good effect of anti-tuberculosis drug treatment.
It is worth mentioning that lung cancer can coexist with tuberculosis in a few patients. Since there is no special clinical manifestation and the X-ray signs are easily ignored, clinicians are often satisfied with the diagnosis of tuberculosis and ignore the co-existing cancerous lesions, which often delays the early diagnosis of lung cancer. Therefore, for middle-aged or older patients with pulmonary tuberculosis, the presence of mass shadows in the focal area of pulmonary tuberculosis or other lung fields, the lung lesions not improving after anti-tuberculosis drug treatment, but the mass shadows increasing in size or accompanied by lung segment or lobe atelectasis and widening of the shadow of one lung door, etc. should raise high suspicion of coexistence of tuberculosis and lung cancer, and further sputum cytology and bronchoscopy must be performed.
(B) Inflammation of the lung
1. Bronchopneumonia Obstructive pneumonia arising from early lung cancer is easily misdiagnosed as bronchopneumonia. Bronchopneumonia generally has an acute onset, and the symptoms of infection such as fever and chills are obvious, and the symptoms disappear rapidly after antibacterial drug treatment, and the lung lesions are absorbed more quickly. If the inflammation is slowly absorbed or recurring, further in-depth examination should be conducted.
2.Lung abscess When the central part of lung cancer is necrotic and liquefied to form cancerous cavity, the X-ray signs are easily confused with lung abscess. Cases of lung abscess often have a history of aspiration pneumonia. In the acute stage, there are obvious symptoms of infection, and the sputum is large, purulent and smelly; on X-ray, the cavity wall is thin, the inner wall is smooth and there are fluid planes, and the lung tissue or pleura around the abscess often has inflammatory lesions. The contrast agent can enter the cavity during bronchography, and is often accompanied by bronchial dilatation.
(C) Other thoracic tumors
Benign lung tumors Benign lung tumors must sometimes be distinguished from peripheral lung cancer. Benign lung tumors generally do not present clinical symptoms, grow slowly and have a long course. On the X-ray film, it shows a nearly round block shadow, which may have calcification points, neat outline, clear boundary and no lobar shape.
2.Isolated metastatic carcinoma of the lung Isolated metastatic carcinoma of the lung is difficult to be distinguished from primary peripheral type lung cancer. The differential diagnosis mainly relies on detailed medical history and symptoms and signs of the primary carcinoma. Metastatic carcinoma of the lung generally presents less respiratory symptoms and sputum blood, and sputum cytology examination is not easy to find cancer cells.
3.Mediastinal tumor Central type lung cancer may sometimes be confused with mediastinal tumor. Diagnostic pneumothorax can help to clarify the location of the tumor. Mediastinal tumors are less likely to present with hemoptysis, and sputum cytology fails to find cancer cells. Bronchoscopy and bronchogram can help in the differential diagnosis. Mediastinal lymphoma is more often seen in young patients, often bilateral, and may have systemic symptoms such as fever.
Predicting primary tumor by X-ray features of lung metastasis
1.Primary tumor is inferred from the shape and margin of metastases: ①sarcoma lung metastases are mostly spherical in shape, with the smoothest margin and higher density. The margins are sharp before chemotherapy and often become irregular due to chemotherapy or bleeding in the marginal area. The thick lung texture with bead-like and corn-like changes can be seen in dynamic observation, which is often the early metastatic sign of choriocarcinoma. After the primary foci are removed and effective anti-cancer treatment is run for 2-3 weeks, the lung metastases shrink or disappear quickly. This phenomenon is also seen in testicular embryonic cell carcinoma, but rarely in other malignant tumors. (5) The cancer nodules of lung metastasis of kidney cancer can be in the shape of “shell” shadows.
2.The primary tumor can be inferred from the multiplication time, cavity, pneumothorax, calcification and ossification of metastases: the multiplication time of sarcoma and choriocarcinoma is shorter, about 10~12d; that of seminoma is second, about 24~48d; that of squamous carcinoma is second, about 50~60d; that of adenocarcinoma is longer, about 75~90d; and that of thyroid carcinoma is longer, about several years. About 4%-9% of the lung lesions can form cavities, especially in the upper lobes. Among them, squamous carcinoma is the most common, followed by female germline carcinoma. Lung metastases from adenocarcinoma are more common in colorectal carcinoma, which can also form multiple cavities. The cavity is caused by necrosis in the center of the lesion, occasionally there can be liquid flat. The cavity can be caused by chemotherapy, there are two kinds of cavities, thick-walled and thin-walled, the former is more cancerous, the latter is more sarcoma. In metastases near the subpleural area, tissue necrosis and formation of bronchopleural fistula are the causes of pneumothorax, and the appearance of pneumothorax is often the precursor of pulmonary metastasis from osteosarcoma. The cavities of pulmonary metastases in the head and neck are small and thin-walled, and those of metastases from germline cancers are large and thick-walled. Calcification or ossification is suggestive of sarcoidosis or malignant tumor. However, calcification has also been reported in metastases from chondrosarcoma, synovial sarcoma, giant cell tumor, colon cancer, ovarian cancer, breast cancer, and thyroid cancer.
Differentiation of primary lung tumors from metastatic lung tumors?
Isolated nodules in the lung following a history of extra-pulmonary tumor should be considered first for metastatic lung cancer. For solitary nodular pulmonary metastases, differentiation from multiple primary carcinomas in the lung, i.e., double or multiple primary carcinomas, should be emphasized. Among the isolated lesions in the lungs of malignant tumor cases, about 20%-60% can be primary lung cancer, while the true lung metastasis can be only 23%-46%.
(A) Exclusion rule
1.The primary tumor is sarcoma or malignant melanoma, and most of the intrapulmonary masses are metastatic.
2.The primary tumor is highly differentiated squamous cell carcinoma or breast cancer, and the intrapulmonary masses are more likely to be multiple primary carcinomas.
3.The primary tumor is adenocarcinoma or hypofractionated carcinoma, and intrapulmonary masses are more likely to be metastatic or have equal chance of primary and metastatic carcinoma.
4.If the multiplication time of single nodal shadow in the lung is <10d or >1 year, then most of the malignant tumors can be excluded, but we should still be alert to the exceptions.
(A) Esophageal cardia failure Patients are mostly young women with a long course of disease and symptoms are sometimes mild and severe. A barium esophageal examination reveals a smooth funnel-shaped stricture at the lower end of the esophagus, which can be dilated with the application of antispasmodics.
(b) Benign esophageal stricture can be caused by scarring caused by accidental swallowing of corrosive agents, esophageal burns, foreign body injuries, chronic ulcers, etc. The duration of the disease is long, and the dysphagia develops to a certain degree without aggravation. It can be identified by detailed medical history and barium X-ray examination.
(c) Benign esophageal tumors Mainly rare smooth muscle tumors, with a long course and intermittent dysphagia. barium X-ray examination can show round, oval or lobulated filling defects in the esophagus with neat margins and normal surrounding mucosal lines.
(D) Hysterical ball syndrome Most often seen in young women, with a ball-like foreign body sensation in the pharynx that disappears when eating, often triggered by psychological factors. This disease actually does not have organic esophageal lesions, and it is not difficult to differentiate it from esophageal cancer.
(e) Iron deficiency pseudomembranous esophagitis Mostly in women. In addition to dysphagia, there may be small cell hypochromic anemia, lingual inflammation, lack of gastric acid and regurgitation.
(f) Peri-esophageal organ lesions such as mediastinal tumors, aortic aneurysms, enlarged thyroid gland, enlarged heart, etc. Except for mediastinal tumor invading into esophagus, barium X-ray examination can show smooth indentation of esophagus with normal mucosal pattern.
Before diagnosing esophageal cancer, it should be differentiated from the following diseases
1. esophagitis and esophageal epithelial cell hyperplasia Some scholars believe that esophageal epithelial cell hyperplasia is the precancerous lesion of esophageal cancer. These patients often have symptoms similar to early esophageal cancer, and X-ray examination often has no abnormal findings. They can be differentiated by esophageal laparoscopic cytology, endoscopic staining and endoscopic ultrasonography, but regular review is often required.
2.Esophageal functional (motor) disorders such as esophageal spasm, neurological dysphagia, esophageal cardia achalasia, etc. Especially cardia achalasia can sometimes be accompanied by adenocarcinoma of cardia, which is characterized by dysphagia, no contraction and peristalsis of esophageal body, smooth esophageal mucosa, and “beak”-like narrowing of cardia on X-ray.
3.Extra-esophageal pressure changes Congenital abnormalities of blood vessels adjacent to the esophagus, aortic aneurysm, intrathoracic thyroid, mediastinal tumor, enlarged mediastinal lymph nodes, prolonged aortic arch condensation, etc. Although the patient has difficulty swallowing, the esophageal mucosa is intact and it is not difficult to distinguish it from esophageal cancer by careful examination.
4.Benign esophageal stricture and esophageal diverticulum Benign esophageal stricture is mostly the sequelae of chemical burns, or it may be the scar stricture caused by esophagitis. Esophageal diverticulum can be divided into two types.
(1) Invagination type: It is often caused by mediastinal lymph node tuberculosis or inflammation producing scar pulling the esophageal wall, with wide diverticulum entrance, often asymptomatic and less common.
(2) bulging type: the mucosa and submucosa layer through the esophageal wall of the muscle layer to the outward expansion of the formation, diverticula once hanging, food can not be completely emptied, the symptoms are more obvious, but also see the reports of cancer.
5.Benign esophageal tumor is most common in smooth muscle tumor, which can occur in any part of the esophagus, mostly in the lower part of the esophagus, followed by the middle part and least in the upper part. On X-ray, a smooth half-moon shaped filling defect with intact mucosa and smooth passage of barium can be seen, and the upper esophagus of the tumor is not dilated. Endoscopic examination shows a bulging mass in the lumen of esophagus with color change in the surface mucosa, but the mucosa is smooth without erosion and ulceration, and there is a sliding sensation when the endoscope passes. Endoscopic ultrasonography shows a hypoechoic sound image with clear boundaries, smooth shape and regular contour, and can identify the layer to which it belongs.
Another common benign tumor is esophageal polyp, mostly found in the cervical esophagus and near the cricopharyngeal muscle. The polyp originates from the submucosa of the esophagus and grows into the lumen, often with a short or long tip. x-ray shows that the lumen of the esophagus is enlarged in the shape of a shuttle, and the lumen of the upper esophagus is not obviously dilated. Malignant changes are occasionally seen, and ulceration of the mucosa can be seen in the case of malignant changes, which sometimes needs to be distinguished from intraluminal esophageal cancer. Other benign tumors, such as esophageal granular cell myoblastoma, esophageal hemangioma and esophageal adenoma, are rare and can be diagnosed through esophagoscopy and tissue examination.
Other malignant tumors such as carcinosarcoma, sarcoma (including fibrosarcoma, rhabdomyosarcoma, smooth muscle sarcoma), malignant lymphoma, malignant melanoma, and leptomeningeal cell carcinoma, etc., whose clinical manifestations, X-ray examination and endoscopic examination are very similar to esophageal cancer.
Differential diagnosis of mediastinal tumor
1. Central type lung cancer has respiratory symptoms such as cough and sputum, and X-ray shows a mass in the hilum, which is semi-circular or lobulated. Tumor can often be seen in bronchial examination, and tumor cells can be found in sputum.
2.Mediastinal lymphatic tuberculosis Most often seen in children or adolescents, often without clinical symptoms. A few are accompanied by mild toxic symptoms such as low-grade fever and night sweats. Round or lobulated masses can be seen at the pulmonary hilum, often accompanied by pulmonary tuberculosis lesions. A round or lobulated mass may be seen at the hilum, often with pulmonary tuberculosis foci. Sometimes calcified spots can be seen in the lymph nodes. In case of difficulty in differentiation, tuberculin test may be performed or short-term anti-tuberculosis drugs may be given.
3.Aortic aneurysm Most often seen in older patients. On physical examination, a vascular murmur can be heard, and dilated pulsations can be seen on fluoroscopy. Retrograde aortography can make a clear diagnosis.
1.Mediastinal lymph node metastases
Most of them are secondary to malignant carcinoma of lung, gastrointestinal tract, kidney, testis, uterine cervix, breast, etc. They are often multiple, or occasionally single and isolated in the mediastinum, and the X-ray shows round, ovoid, lobulated, irregular and dense shadows in the middle mediastinum. The margins are sharp. It can be differentiated by the history of the primary tumor and other clinical findings.
2. Intrathoracic thyroid
Mostly goiter, thyroid cyst or adenoma, mostly benign, but also acquired, associated with the thyroid gland, extending from the thyroid gland in the neck down to the anterosuperior mediastinum, usually asymptomatic, but if the enlargement produces compression may appear dyspnea, wheezing and retrosternal discomfort. /X-rays usually show an anterosuperior mediastinal mass that is prominent on one or both sides of the upper mediastinum. The density is homogeneous, the margins are smooth, or slightly lobulated, and there may be calcification. The lesion is anterior to the trachea and the trachea may be pushed laterally or posteriorly, and the circumferential encasement may also narrow the trachea. The mass can be palpated at the sternotomy and moved up and down.
3.Malignant lymphoma
Malignant lymphoma originating in the mediastinum is rare, but it is mostly a systemic malignant lymphoma with mediastinal invasion. Clinically, there are fever, cough, chest tightness, chest pain, weakness, night sweating, and also superior vena cava syndrome, and the lesion is mostly located in the paratracheal area and under the bulge. Advanced lesions may invade the lungs and heart. Most of them can be diagnosed, but if the diagnosis is difficult to determine (biopsy cannot be taken), the disease can be easily diagnosed if the lesion shrinks rapidly with one or two chemotherapy treatments.
4. Mediastinal lymph node tuberculosis
The symptoms are not obvious, mostly in young and middle-aged patients, often with weakness and cough, night sweats, low fever, reduced appetite, weight loss, X-ray lesions are mostly located in the upper mediastinum on one side, more on the right side, with round and ovoid shadows. The authors report that the clarity of the shadow is better in the ortho than in the lateral position. Blood sedimentation is more than 40 mm/h, and skin OT test is mostly positive.
5. Mediastinal lymphadenitis or granuloma
There are many causes of mediastinal lymph node granuloma, mostly tuberculosis, in addition to histoplasmosis, tuberculosis and silicosis. The incidence of the disease is mostly in middle-aged and young people, with a long course and good general condition. It may present with cough, fever, headache, chills, and dyspnea. In recent years, tuberculosis has been on the rise in this disease. It presents as a round, oval or lobulated mediastinum with smooth, neat and uniform margins. If there is no primary tumor, tuberculosis is excluded, and hormones are used, nodular disease can be treated quite well.