Bronchial adenoma is a neoplasm originating from the epithelium of the ducts and mucous glands of the bronchial wall. Clinically, bronchial adenoma is manifested by shortness of breath, stridorous breathing, cough, hemoptysis, signs of inflammation of the respiratory tract. Adenomatous bronchial tumor is detected by radiography, tomography, bronchoscopy and bronchography, endoscopic biopsy. The neoplasm is subject to surgical removal; depending on the clinical situation, endoscopic removal of the tumor, circular or terminal bronchial resection, various types of lung resection, pneumonectomy can be performed.
14.3 Bronchial and lung adenoma
Tumors developing in the bronchi can be both benign and malignant. The number of malignant tumors includes bronchogenic lung cancer. Benign bronchial tumors are mainly represented by adenomas. In general, benign neoplasms of the bronchi are much less common than malignant ones, in about 5-10% of cases in the general structure of tumor lesions of the respiratory tract.
Among benign tumors, adenomas account for about 60-65%. Bronchial adenomas are epithelial tumors that develop mainly from the glands of the mucous membrane of the bronchial tree. In pulmonology, bronchial adenoma is considered as a benign tumor with a high potential for malignancy, since various types of adenomas are prone to recurrence and malignancy. Bronchial adenoma is more often diagnosed in women aged 35-50 years.
Causes of bronchial adenoma
Reliable causes of bronchial adenomas are unknown. It is assumed that the following factors may play a role in their development:
- Exogenous influences. Smoking (active and passive), occupational factors (working with arsenic, nickel, asbestos, etc.), environmental problems.
- Diseases of the bronchi and lungs. The pathogenetic connection of bronchial adenoma with other bronchopulmonary pathology is not excluded: COPD, bronchial asthma, chronic bronchitis, recurrent and prolonged pneumonia, etc.
- Hormonal imbalance. Considering that adenomas of any localization (adenoma of the prostate, breast, thyroid, salivary glands, gastrointestinal tract, bronchus) arise from the glandular epithelium, the involvement of endocrine mechanisms in their occurrence is likely.
Morphologically, “bronchial adenoma” is a collective concept that includes tumors that are diverse in structure and cellular composition. Taking into account the pathohistological structure, several types of bronchial adenomas are distinguished: carcinoid, mucoepidermoid, cylindromatous and mixed.
In more than 80% of clinical practice, adenomas of the carcinoid type (bronchial carcinoids) are found. According to their microscopic structure, they are represented by proliferating cells emanating from the ciliary epithelium or bronchial glands. The presence of a significant number of argentaffin structures (stained with silver salts) in the cells is characteristic, which makes it possible to classify this type of bronchial adenoma as typical carcinoids.
There are a large number of vessels in the place where the carcinoid grows, which explains the tendency of the tumor to hemorrhages. The adenoma is usually firmly connected to the bronchial wall and in some cases penetrates deep into its thickness. It is assumed that bronchial carcinoids, as well as carcinoids of the digestive tract, secrete serotonin and adrenaline, so this type of bronchial adenoma can cause vegetative disorders: a feeling of heat, dizziness, bronchospasm attacks, allergic dermatoses, etc.
Among the carcinoid adenomas of the bronchus, there are typical highly differentiated carcinoid, atypical moderately differentiated and anaplastic low-differentiated carcinoid. Malignancy of carcinoid bronchial adenomas occurs in 5-10% of cases. A malignant carcinoid is characterized by infiltrative growth and the ability to hematogenous and lymphogenic metastasis to distant organs – another lung, brain, liver, bones, kidneys, pancreas. Unlike bronchogenic cancer, malignant bronchial adenoma is characterized by slow growth and late metastasis, and its radical removal gives good long-term results.
The second place in the frequency of detection (about 10%) is occupied by bronchial adenomas of the cylindromatous type (cylindromas). Microscopically, they consist of cylindrical or prismatic epithelium. Significantly less common (less than 1%) are bronchial adenomas of the mucoepidermoid type (mucoepidermoids), represented by glandular-cystic formations filled with mucosal mass. Bronchial adenomas of mixed type combine the structure of the cylinder and carcinoids. Central and peripheral bronchial adenomas are distinguished by localization.
Among bronchial adenomas, the least malignant course is characteristic of carcinoid tumors. Bronchial adenomas usually reach sizes 2-3 cm across, have a smooth, sometimes lobed surface of pinkish-red color. Adenomas can have endobronchial, extrabronchial (extrabronchial) and mixed growth. Endobronchial adenoma grows into the bronchial lumen, lifting the mucous membrane, causing its atrophic changes and ulceration.
Endobronchial growth is accompanied by an increase in bronchial obstruction, up to the complete closure of the bronchial lumen. As the tumor grows, lung atelectasis may occur, chronic pneumonia with frequent exacerbations, pneumosclerosis, bronchiectasis may develop. Extra-bronchial growth of bronchial adenoma is characterized by the spread of the tumor into the thickness of the bronchial wall or external localization.
With a mixed growth pattern, the bronchial adenoma has the appearance of an hourglass, dumbbell or iceberg; at the same time, the endobronchial and extra-bronchial parts of the tumor are separated by a constriction between the expanded and destroyed cartilages of the bronchus. In 60% of cases, adenomas affect the lobular or segmental bronchi; in 20% – the main bronchi; in another 20% – bronchioles.
Symptoms of bronchial adenoma
The severity of symptoms depends on the localization of the tumor, the degree of bronchial obstruction, and the development of complications. There are three periods in the clinical course of central bronchial adenoma. In the first period, the adenoma does not cause a gross violation of bronchial patency. Clinical manifestations include dry cough, general malaise, hemoptysis.
In the second period, associated with a sharp violation of bronchial patency, pathological changes develop in the lung tissue and pleura (repeated bronchopneumonia, atelectasis, pleurisy), shortness of breath, stridorous or wheezing, cough with sputum, fever, pulmonary bleeding. The third period is characterized by complete obstruction of the bronchial lumen by adenoma, which is accompanied by the development of persistent lung atelectasis with poststenotic bronchiectasis and the addition of purulent infection.
The clinical picture of the third period is determined by an increase in body temperature to 38-39 ° C, cough with copious discharge of purulent sputum, hemoptysis, chest pain, signs of intoxication, general weakness, weight loss, anemia. Possible development of pulmonary heart failure. In persons with peripheral lesions, the course of bronchial adenoma is usually asymptomatic.
Bronchial carcinoids in 2-4% of cases are accompanied by the development of carcinoid syndrome. In this case, there are periodic flushes of blood to the head and upper extremities, a feeling of heat, pinkish-red spots on the skin of the face, bronchospasm, fluctuations in blood pressure, paroxysmal abdominal pain, diarrhea. The severity and frequency of seizures increases with malignancy of bronchial adenoma of the carcinoid type.
Diagnostics of bronchial adenoma
Bronchial adenoma is not always detected in a timely manner during preventive fluorography. Even on radiographs, with the localization of adenoma in the main and lobar bronchi, pathological changes are usually invisible; only on tomograms can defects of the bronchial wall be determined. The X-ray picture of bronchial adenoma depends on the degree of bronchial obstruction, the caliber of the affected bronchus, and the duration of the process.
With complete bronchial obstruction, lung radiography reveals partial or complete lung atelectasis; in the case of partial obstruction, signs of hypoventilation are determined. The most convincing data for bronchial adenoma are obtained with CT and MRI of the lungs, lung scintigraphy. To clarify the nature of the neoplasm and its relationship with the bronchial wall allows X-ray contrast examination – bronchography.
In most cases, the final diagnosis of bronchial adenoma is facilitated by diagnostic bronchoscopy with biopsy. In the case of endobronchial growth, it is possible to visualize a rounded pink formation with a shiny smooth or finely rounded surface, easily bleeding on contact. Bronchial adenoma, which has a leg, has high mobility; in the event that the tumor grows on a wide base or has the appearance of an “iceberg”, it is not possible to shift it during bronchoscopy.
An endoscopic biopsy followed by histological examination makes it possible to clarify the type of bronchial adenoma and the degree of its goodness. In order to assess the severity of obstructive and restrictive disorders, spirometry is performed. To exclude adenomas of a different localization, it is advisable to carry out TRUS (in men), ultrasound of the mammary glands (in women), EGD, colonoscopy, ultrasound of the thyroid gland, kidneys and adrenal glands, salivary glands.
Treatment of bronchial adenoma
Due to the risk of complications (suppuration, bleeding, malignancy), bronchial adenomas are subject to surgical removal as soon as possible. The nature and scope of the intervention is determined by the localization, size, growth characteristics, histological structure of bronchial adenoma, the development of secondary changes in lung tissue.
In the early period, with a deliberately benign bronchial adenoma of central localization with endobronchial growth having a thin leg, endoscopic removal of the tumor can be performed. However, endobronchial intervention is associated with the likelihood of insufficient radicality of the operation, a high risk of bleeding, the need for repeated endoscopic control and bronchial biopsy.
In most cases, the removal of bronchial adenoma on a narrow leg is performed by bronchotomy or final resection of the bronchus. With adenomas having a wide base, circular resection of the bronchus with the imposition of an interbronchial anastomosis is indicated. These types of operations, limited to economical bronchial resection, can be performed only with histologically confirmed benign formations and functionally complete lung tissue.
In the case of limited irreversible changes in lung tissue distal to bronchial obstruction by a tumor (bronchiectasis, poststenotic lung abscesses, fibrosis), marginal resection, segmentectomy, lobectomy or bilobectomy is performed. With pathological changes in the entire lung, the only possible intervention is a pneumonectomy.
Untimely diagnosis of bronchial adenoma excludes the possibility of sparing operations and dictates the need for large-scale lung resections. After radical resection of bronchial adenoma, the 5-year survival rate is 96%. In some cases, local relapses, tumor malignancy and distant metastasis of bronchial adenoma are possible. Patients who have undergone bronchial adenoma removal should be under the supervision of a pulmonologist (thoracic surgeon), undergo regular X-ray and endoscopic monitoring.