Squamous cell lung cancer is a histological type of bronchopulmonary cancer resulting from squamous metaplasia of the bronchial epithelium. Clinical manifestations depend on the location of the tumor (central or peripheral lung cancer). The disease can occur with cough, hemoptysis, chest pain, shortness of breath, pneumonia, pleurisy, general weakness, metastasis. Lung cancer is diagnosed according to X-rays, tomography, bronchoscopy; morphological diagnosis is based on the results of cytological and histological analysis of bronchoalveolar flushes, biopsies. Treatment is surgical and/or chemoradiotherapy.
ICD 10
C34 Malignant neoplasm of bronchia and lung
Meaning
Squamous (epidermoid) lung cancer is a malignant tumor that develops from metaplastic cells of the bronchial squamous epithelium. Normally, there are no flat epithelial cells in the lining of healthy bronchi, so the development of squamous cell carcinoma is preceded by epidermoid metaplasia – the process of transformation of the ciliated epithelium into a flat one. Disease accounts for more than half (about 60%) of all histological forms of lung cancer. It mainly affects men over 40 years of age. Up to 70% of tumors of this type are localized in the root of the lung, in a third of cases peripheral lung cancer is detected. The relevance of disease for clinical pulmonology lies primarily in its high prevalence and potential elimination of risk factors for the disease.
Causes of squamous cell lung cancer
The cause of squamous cell metaplasia and the subsequent development of the tumor process is the effect of toxic substances on the bronchial mucosa. Most patients suffer from long-term nicotine addiction, so smoking (including passive) is considered the main risk factor for this pathology. The role of aerogenic pollutants inhaled with atmospheric air (sulfur dioxide, carbon monoxide, nitrogen dioxide, acids, formaldehyde, solid particles, etc.) is great in bronchial damage. Background pathologies, often preceding squamous cell lung cancer, include pneumoconiosis, chronic bronchitis, pneumonia, tuberculosis. It is known that infection with certain viruses (cytomegalovirus, human papillomavirus) can cause atypical metaplasia of the bronchial epithelium.
Normally, the walls of the bronchi are lined with cylindrical ciliated epithelium, on the cilia of which the smallest impurities contained in the inhaled air settle. The movement (flickering) of the cilia ensures the removal, expulsion of harmful particles from the respiratory tract, i.e. with their help, the mechanism of self-purification of the bronchi is realized. Under the influence of harmful aerogenic loads, the bronchial epithelium begins to change, adapt to constant aggressive influences. There is a gradual disappearance of cilia, a change in the shape (flattening) of epithelial cells and their keratinization. In the new conditions, the lungs become open to the penetration of foreign particles, and the constant accumulation of sputum in the bronchi contributes to the development of chronic background diseases. Some researchers consider epidermoid metaplasia of the epithelium as an early, preinvasive stage of squamous cell lung cancer.
Classification
The defining microscopic criteria for squamous cell lung cancer are: signs of keratinization, the presence of intercellular bridges and the formation of horny pearls. Based on the severity of these signs, the degree of differentiation of the tumor is judged, distinguishing highly differentiated (keratinizing), moderately differentiated (non-keratinizing) and low-differentiated squamous cell lung cancer.
Histologically, a highly differentiated tumor is represented by layers of large cells, with clearly defined nuclei, pronounced keratinization of cells, intercellular bridges and horny pearls. A moderately differentiated form of cancer is also represented by large polygonal cells that are in good contact with each other, have a developed cytoplasm, but with fewer intercellular bridges; keratin is detected only in some cells. Low-grade squamous cell lung cancer is characterized by a predominance of small cells with poorly developed nuclei, organelles and desmosomal contacts.
According to the anatomical classification, peripheral and central squamous cell lung cancer are distinguished; atypical forms (disseminated, mediastinal) are less common.
Symptoms of squamous cell lung cancer
Clinical manifestations largely depend not on the histological type and degree of differentiation of lung cancer, but on the anatomical localization of the tumor, its size, the nature of growth and the rate of metastasis. Therefore, the symptoms of squamous cell lung cancer are generally similar to other types of cancer (large cell, small cell, adenocarcinoma).
In 5-15% of patients, the early stages of cancer are clinically asymptomatic; in this case, the tumor may be accidentally detected during a fluorographic examination. All symptoms of squamous cell lung cancer are divided into primary (local), secondary (caused by complications, metastasis or cancer intoxication). Primary symptoms are usually relatively early and are associated with the growth of the primary tumor node. The most persistent complaints include cough, chest pain, shortness of breath. The cough is dry at first, nadsadny; in half of the patients with the central form of lung cancer, hemoptysis is observed, in the later stages turning into pulmonary bleeding.
As the tumor process spreads, secondary symptoms are added to the local manifestations of squamous cell lung cancer. They are associated with both local complications (complications of an inflammatory nature, germination or compression of neighboring structures), and with distant metastasis, as well as the general effect on the body of a malignant tumor. With the development of obstructive pneumonia, patients develop febrile fever, a wet cough with the discharge of mucopurulent sputum. With compression or germination of nearby organs, dysphagia, hoarseness of the voice, Gorner syndrome, intense pain in the neck and shoulder, arrhythmia may bother.
Common symptoms include general weakness, anorexia, weight loss, cachexia. In epidermoid lung cancer, hypercalcemia and hypophosphatemia may develop due to ectopic production of parathyroid hormone and prostaglandins. Extrathoracic metastases (to the liver, bones, adrenal glands, brain) are detected in half of patients who died from squamous cell lung cancer.
Diagnostics
The primary diagnostic complex includes an assessment of anamnesis, complaints, physical and X-ray examination. Lung radiography can detect lung cancer in 80% of cases, determine the size of the tumor and its location, the involvement of intra-thoracic lymph nodes. chest CT is used to study the spread of bronchopulmonary cancer.
With the help of bronchoscopy, signs of tumor growth are visually confirmed or excluded. A more detailed study of the cellular composition is performed by cytological analysis of sputum and bronchoalveolar flushing. The final verification of the histological status is possible only after a pinch or a trans-bronchial biopsy of the tumor and a morphological examination of the biopsy. Squamous cell carcinoma requires differentiation from other types of malignant lung tumors, as well as metastases of squamous cell carcinoma of other localization.
Treatment for squamous cell lung cancer
Planning of therapeutic tactics for squamous cell lung cancer is based on knowledge of the localization and prevalence of the process. If possible, radical removal of the tumor is resorted to excision of the primary focus and lymph nodes and mediastinal tissue affected by metastases. The volume of resection usually ranges from lobectomy to extended pneumonectomy.
Chemoradiotherapy of squamous cell lung cancer can be carried out as part of a radical program or with a palliative purpose. Both tumor location zones and metastasis zones are exposed to radiation. Polychemotherapy (cyclophosphane, vincristine, methotrexate) is usually used in addition to radiation therapy in inoperable patients. Symptomatic therapy (detoxification, anesthesia, psychological help) is dictated by the patient’s condition. Immunochemotherapy using growth factor inhibitors and angiogenesis is a new, but rather promising method of treating squamous cell lung cancer.
Forecast
The five-year survival rate after treatment for squamous cell lung cancer is 60-80%. When lung cancer is detected at the second stage, this indicator decreases to 40%, at the third – to 15-18%. The prognosis is significantly affected by the degree of differentiation of squamous cell lung cancer – the lower it is, the less sensitive the tumor is to chemoradiotherapy and its metastatic spread occurs earlier. The median survival of patients in the absence of treatment is on average 6-8 months.
Literature
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