Bronchial carcinoid tumor is a rare neoplasm from the group of neuroendocrine tumors, affecting mainly large bronchi. It is characterized by relatively slow growth with the ability to metastasize. It is considered as a potentially malignant neoplasia. It is manifested by coughing, shortness of breath, hemoptysis and recurrent pneumonia. Carcinoid syndrome rarely develops. The diagnosis of “bronchial carcinoid tumor” is made on the basis of radiography, CT of the lungs, bronchoscopy, laboratory tests and other studies. Surgical treatment, more often in the volume of segment-, forehead-, pneumonectomy; bronchoplastic interventions are possible.
General information
Bronchial carcinoid tumor is a rare tumor originating from hormonally active cells of the diffuse neuroendocrine system. It accounts for 1-2% of the total number of lung malignancies and 20-30% of the total number of carcinoids. It ranks second in the prevalence of carcinoids after similar neoplasias of the gastrointestinal tract. Bronchial carcinoid tumor occurs in a wide age range, the literature describes cases of the disease in patients from 10 to 83 years old. The average age at the time of diagnosis is 45-55 years. There is a slight predominance of female patients. Bronchial carcinoid tumor is the most common oncological lesion of the lungs in children, it develops more often in late adolescence.
In recent years, there have been reports of an increase in the number of bronchial carcinoids, however, experts believe that this is due rather to the use of modern laboratory and instrumental techniques that allow the diagnosis of asymptomatic and low-symptomatic tumors than to a true change in the prevalence of the disease. The etiology of bronchial carcinoid tumor has not been clarified, in some cases a hereditary syndrome is revealed that causes the development of multiple neuroendocrine tumors. There is no connection with risk factors that increase the likelihood of lung cancer (smoking, occupational hazards, chronic lung and bronchial diseases). In more than 60% of cases, bronchial carcinoid tumor is localized in the central bronchi, often at the root of the lung. Treatment is carried out by specialists in the field of oncology, pulmonology and thoracic surgery.
Classification and pathanatomy
According to the WHO classification in the 2010 edition, taking into account morphological features, the following groups of bronchial carcinoids are distinguished:
- A highly differentiated carcinoid with a favorable prognosis.
- A moderately differentiated (atypical) carcinoid with an uncertain prognosis.
- Large-cell and small-cell neuroendocrine lung cancer with an unfavorable prognosis.
Highly differentiated neoplasias account for more than 60% of the total number of bronchial carcinoids. Characterized by an extremely sluggish flow. Metastases are detected in 10-15% of patients. Metastatic lesion of mediastinal lymph nodes, bones and liver is possible, less often – soft tissues. Moderate and low-grade bronchial carcinoids account for less than 30% of the total number of neuroendocrine tumors of this localization, usually develop at the age of over 60 years and are characterized by a more malignant course. They are more often localized in the peripheral parts of the lungs, grow rapidly, metastasize early to the lymph nodes of the mediastinum. Metastases are found in 40-50% of patients.
All types of bronchial carcinoid tumor originate from epithelial endocrine cells. Tumors usually grow endobronchially and when they reach a certain size, they block the lumen of the bronchus, causing atelectasis or obstructive pneumonia. They consist of small polygonal cells. Bronchial carcinoid tumor cells are grouped into strands, clusters and pseudoelastic structures. In the cells of highly differentiated neoplasias, an insignificant number of mitoses are detected. The cells of medium- and low-differentiated bronchial carcinoid tumor are characterized by pronounced atypism and a large number of mitoses. Areas of necrosis can be detected in the tissue of such tumors.
Symptoms
In 30% of patients, bronchial carcinoid is asymptomatic and is detected during the next medical examination or examination due to suspicion of another pathology. In other cases, the manifestations depend on the degree of malignancy and localization of the neoplasm. With highly differentiated centrally located bronchial carcinoids, symptoms may appear many years before the diagnosis. As a rule, the leading role in the clinical picture is occupied first by a dry, and then by a wet cough, because of which some patients are diagnosed with chronic bronchitis.
As the carcinoid grows, bronchial obstruction becomes more pronounced. With large tumors, recurrent pneumonia develops. Atelectasis of the lobe of the lung or the entire lung is possible. Sometimes there is hemoptysis. Peripheral malignant bronchial carcinoids do not manifest themselves in the early stages, but they progress much faster than the central benign ones. Paraneoplastic syndrome in this pathology is rarely detected. Carcinoid syndrome, accompanied by hot flashes, hyperemia of the upper body, bronchospasm, tachycardia, arterial hypotension, diarrhea and heart valve damage, is found in 2% of patients with bronchial carcinoid. As a rule, the development of this syndrome is caused by distant metastasis. Less often, an invasive procedure (usually a biopsy) or surgical intervention becomes the impetus for the occurrence of carcinoid syndrome.
In 2% of patients with bronchial carcinoid, Cushing’s syndrome is detected, manifested by characteristic obesity, striae, acne, skin pigmentation, hirsutism, high blood pressure, osteoporosis and some other symptoms. With metastasis of bronchial carcinoid into mediastinal lymph nodes, swelling of the head and neck, dilation of the veins of the anterior surface of the chest, voice changes, dysphagia and breathing difficulties are possible. With liver metastases, jaundice and hepatomegaly develop. In advanced cases, patients with bronchial carcinoid have weight loss, decreased appetite, increased body temperature and other symptoms characteristic of the late stages of the oncological process.
Diagnosticsg
The diagnosis is established by an oncologist on the basis of complaints, medical history, objective examination data, laboratory and instrumental research results. The examination program includes a blood and urine test for hormones (including serotonin and chromogranin A). Central bronchial carcinoids can often be detected during bronchoscopy. When detecting peripheral tumors, chest x-ray, CT, MRI, PET, scintigraphy and other studies are used. CT, MRI and abdominal ultrasound are prescribed to detect liver metastases.
Treatment
The main method of treatment of a typical bronchial carcinoid is surgical intervention. Depending on the localization and prevalence of the oncological process, segmentectomy, lobectomy or pneumonectomy are performed. If the tumor is located in the lobular or main bronchus, in some cases, circular resection of the bronchus with the creation of an interbronchial anastomosis is possible. The operation involves the removal of mediastinal lymph nodes. Opinions on the tactics of surgical treatment for atypical low-grade bronchial carcinoids vary. Some experts point to the inexpediency of organ-preserving operations, others note a small number of relapses during economical surgical interventions.
Endoscopic resection in bronchial carcinoid can be palliative in nature or performed before radical surgery. The purpose of endoscopic removal of the tumor in the latter case is to eliminate atelectasis and restore the respiratory function of the affected lung. Chemotherapy and radiation therapy for bronchial carcinoid are ineffective. For diarrhea, codeine and loperamide are prescribed. Bronchospasm is treated with bronchodilators. In the presence of carcinoid syndrome, symptomatic therapy is performed using octreotide.
Forecast
The prognosis for bronchial carcinoid tumor is quite favorable. Prognostically favorable factors are the high level of tumor differentiation and the absence of metastases to mediastinal lymph nodes at the time of surgery. The average five- and ten-year survival rate of patients with typical bronchial carcinoid in the absence of metastases exceeds 90%. With typical neoplasia with lymph node metastases, 90% of patients manage to survive up to 5 years from the moment of surgery, up to 10 – 76%. With atypical bronchial carcinoids with lymph node damage, these indicators decrease to 60% and 24%, respectively.
