Lung cancer, the classification of which will be described in this article, is a very common disease worldwide. Features of its distribution are caused by the release of carcinogenic and toxic substances into the environment, smoking, adverse working conditions, as well as untimely detection of the disease. It should be noted that the disease is characterized by excessive secrecy, being able to disguise itself as various other diseases. And often the cancer is determined by chance or with a thorough diagnosis of any other disease. As with most oncological diseases, the classification of lung cancer is carried out according to certain parameters and indicators. This will be discussed below.
The general principle of systematization
Clinical and pathomorphological properties of this disease are divided into different groups. Classification of lung cancer is carried out depending on the following symptoms:
- Anatomical.
- Morphological.
- According to the classification of TNM.
If we talk about the anatomical classification of lung cancer, then it includes the principles of the distribution of the disease according to the structures that are affected by the oncological process. According to this classification, it is customary to distinguish peripheral and central lung cancer.
Classification of lung cancer by TNM implies the classification of this disease according to the size of the existing tumors, the absence or presence of lymph node lesions, and also the presence or absence of metastases.
What does the morphological systematization say? This classification includes varieties of the tumor development process, where each has its own pathomorphological features.
In addition to the classification of lung cancer by TNM, it is also customary to distinguish this disease by the degree of spread of the tumor process:
- Lymphogenic
- Local.
- Pleurogenic.
- Hematogenous.
Also, with certain varieties, this disease can be divided into stages. Let's take a closer look at the modern classification of lung cancer.
Anatomical
This method is based on the principle of classifying the tumor process by anatomical localization, as well as by the nature of the growth of the tumor in relation to the bronchi. It has already been said above that there is a classification of central lung cancer, as well as peripheral. But to these two varieties it is also customary to add atypical forms of the disease. In addition to the forms described above, the clinical anatomical classification of lung cancer includes some subspecies.
Bronchogenic, or central lung cancer develops in the large bronchi. It is customary to isolate endobronchial, branched and exobronchial cancer in it. The difference in these varieties is based on the nature of tumor growth. With endobronchial cancer, tumor neoplasms grow in the lumen of the bronchus, and externally they look like a polyp with a slightly tuberous surface. As for exobronchial cancer, it is characterized by growth in the thickness of the lung tissue, which is the reason for the difficult patency of the affected bronchus. Branched cancer forms a kind of coupling near the affected bronchus from atypical tissue and spreads in its direction. This view can lead to a uniform narrowing of the lumen of the bronchus.
TNM classification
The TNM classification of lung cancer was first introduced in 1968. Since then, it has been periodically edited and revised. Currently, the seventh time edited classification is used. As a rule, the degree of classification of lung cancer by TMN is divided by the size of the tumor, as well as by the defeat of the lymph nodes. There is also a systematization that takes into account metastatic lung damage.
To size
Consider the international classification of lung cancer by the size of the resulting tumor:
- T0: symptoms of the primary tumor cannot be determined.
- T1: the resulting tumor in size is less than three centimeters, there are no visible sprouts or lesions of the bronchi.
- T2: the size of the resulting tumor is more than three centimeters. In addition, for this classification of lung cancer by stages, the presence of a tumor of any size with germination in the visceral pleura is characteristic.
- T3: the tumor can be represented in any size, but with the condition of its spread to the diaphragm, mediastinal side of the pleura, as well as the chest wall.
- T4: the tumor can be of any size with a significant spread to the structures and tissues of the body. In addition, there is a malignant confirmed nature of pleural effusion.
On the lymph nodes
Classification of lesions of these organs will look as follows:
- N0: there are no regional lymph nodes with metastases.
- N1: pulmonary, intrapulmonary, bronchopulmonary lymph nodes or the lung root lymph nodes are affected.
- N2: lymph nodes of the mediastinal region or bifurcation lymph nodes are affected.
- N3: to the existing lesion is added an increase in the supraclavicular lymph nodes, as well as the root and mediastinum.
By metastases
In addition, there is a classification that takes into account metastatic organ damage:
- M0: distant metastases in this case are absent.
- M1: signs of the presence of distant metastases are detected.
Pathomorphological classification
This method gives specialists the opportunity to assess the structure of tumor cells, as well as individual physiological features of functioning. This histological classification of lung cancer is necessary in order to select the most appropriate method of exposure to a particular type of tumor for the purpose of treating the patient. According to pathomorphological features, lung cancer is divided into the following types:
- Adenocarcinoma of the lungs.
- Large cell lung cancer.
- Small cell carcinoma.
- Squamous cell.
- Solid lung cancer.
- Cancer that affects the bronchial glands.
- Undifferentiated lung cancer.
Large cell
A tumor characterized by a large-cell structure is cancer, during which the cells are clearly visible, large in size, as well as the cytoplasm, which can be seen through a microscope. This cell lung cancer can be divided into five more groups, among which the most common are giant cell and clear cell forms.
Giant cell cancer is a tumor with cells of bizarre, gigantic forms, with a huge number of nuclei. As for the clear cell form, cells with a foamy, light cytoplasm are characteristic of this species.
Adenocarcinoma
This type of lung cancer affects cells in the epithelial row. The structure can produce glands, forming formations of different shapes. Due to the predominant damage to cells of the glandular layers of the epithelium, this species is often called glandular lung cancer. The type of tumor may include different degrees of differentiation of structures, which is why varieties of both low-grade and highly-differentiated adenocarcinomas are distinguished.
It should be noted that the degree of differentiation plays a large role in the nature of the tumor process, as well as during the disease itself. For example, low-grade forms are the most aggressive, and also much more difficult to treat. Highly differentiated forms are most susceptible to treatment.
Squamous
This type of cancer is also commonly referred to the group of the tumor process, which originates from cells of the epithelial row. Tumor cells are presented in the form of peculiar spikes. Squamous cell carcinoma has a feature consisting in the ability of cells to produce keratin, due to which peculiar pearls, or growths, are formed. Thanks to these characteristic growths, this form of cancer is often called keratinized, or pearl cancer.
Small cell
The small cell form is characterized by the presence of cells of the smallest sizes of different shapes. It is usually customary to isolate three varieties of small cell lung cancer: combined, from cells of the intermediate type, as well as oat.
Group of solid crayfish
This group of lung cancer is characterized by the location of its own structures, interconnected by connective tissue. This variety refers to low-grade tumor processes.
Neuroendocrine
This species is very rare in practice when compared with other forms of the tumor process of the lungs. The neuroendocrine form is characterized by slow growth. At the heart of this tumor is the launch of a tumor change in the cells. Neuroendocrine cells have the ability to synthesize various protein substances, as well as hormones. In addition, they can spread throughout the human body.
Under the influence of various factors in these cells, programs of natural growth and aging begin to be disrupted. As a result of this, the cell begins to divide uncontrollably and becomes a tumor.
Despite the fact that tumor neuroendocrine processes spread very slowly throughout the human body, they are included in the list of diseases that require close attention and examination. The reason for this is the fact that these formations have practically no characteristic clinical symptoms and signs, which is why they are difficult to diagnose at an early stage.
In addition, according to its classification, small-cell, large-cell form, as well as carcinoid neuroendocrine lung tumors, are distinguished. Neuroendocrine pulmonary tumor can have different degrees of differentiation and malignancy. In this case, the degree of malignancy will be determined depending on the number of division of tumor cells, as well as their ability to grow. This indicator of a malignant cell for division is denoted by G, and the indicator of proliferative activity of the tumor is usually designated Ki-67. Based on these indicators, three degrees of neuroendocrine malignant tumor are distinguished:
- First degree. A tumor cell can make less than two divisions.
- Second degree. The number of divisions is from two to twenty, and proliferation rates are from three to twenty.
- Third degree. In this case, the cell can make more than twenty divisions. As for the proliferation rate, for this stage it is also more than 20 divisions.
If we talk about the diagnosis of neuroendocrine lung tumors, then it includes the use of radiation methods, which should include magnetic resonance imaging, computed tomography, as well as panoramic radiography of the chest cavity. Diagnostic methods include sputum examination for the presence of atypical cells. There are also specific methods that are aimed at identifying the neuroendocrine characteristics of the process. In most cases, electron microscopy of a tumor biopsy is used for this, as well as the determination of immunological markers.
Using an electron microscope, a specialist can discern in the tumor cells a certain granularity, which is a neuroendocrine granule that is characteristic only of the cells of this system. Neuroendocrine or immunological markers are usually detected by immunohistochemistry. This method involves the processing of sections of the studied materials with special antibodies.