Lung adenocarcinoma (also known as pulmonary adenocarcinoma ) is the most common type of lung cancer, and is characterized by different cellular and molecular features including gland and/or channel formation and/or production of mucus in significant amounts. It is also classified as one of several non-small cell lung cancer (NSCLC), to differentiate it from small cell lung cancers that have different behaviors and prognoses.
Video Adenocarcinoma of the lung
Signs and symptoms
The most common signs of lung cancer include:
- a cough that does not go away or worsens
- blood cough or rust-colored phlegm Chest pain
- , which may be exacerbated by deep breathing, coughing, or laughing
- hoarse voice
- weight loss and loss of appetite
- difficulty breathing
- generally feel tired or weak
- recurrent or unresolved lung infections (eg bronchitis and pneumonia)
- new onset of wheezing without asthma history
Importantly, all of these signs are more frequent because of other non-cancerous causes.
Maps Adenocarcinoma of the lung
Cause
According to the Nurses Health Study, the risk of pulmonary adenocarcinoma increased substantially after the duration of smoking, with a previous smoking duration of 30-40 years which gave a relative risk of about 2.4 compared with never smoking, and a duration of more than 40 years gave a relative risk of about 5.
These cancers usually look peripheral in the lungs, compared with small cell lung cancer and squamous cell lung cancer, both of which tend to be more centrally located, although it may also occur as central lesions. For unknown reasons, it often appears in relation to peripheral lung scarring. The current theory is that scars may occur secondary to tumors, rather than causing tumors. Adenocarcinoma has an increased incidence in smokers, and is the most common type of lung cancer seen in non-smokers and women. The peripheral location of adenocarcinoma in the lungs may be due to the use of filters in cigarettes that prevent larger particles from entering the lungs. Deeper inhalation of cigarette smoke produces peripheral lesions that often occur in pulmonary adenocarcinoma. Generally, adenocarcinoma grows more slowly and forms a smaller mass than other subtypes. However, he tends to metastasize at an early stage.
Molecular biology
Chromosom rearranging
Three receptor tyrosine kinases associated with the membrane are repeatedly involved in rearrangements in adenocarcinoma: ALK, ROS1, and RET, and more than eighty other translocations have also been reported in pulmonary adenocarcinoma.
Targeted therapy: ALK and ROS1 protein fusions are equally sensitive to treatment with novel ALK tyrosine kinase inhibitors (see Genetic Atlas and Cytogenetics in Oncology and Hematology,).
Gene mutation
Mutation of common genes in pulmonary adenocarcinoma affects many genes, including EGFR (20%), HER2 (2%), KRAS, ALK, BRAF, PIK3CA, MET (1%, associated with resistant disease), and ROS1. Most of these genes are kinases, and can mutate in various ways, including amplification. The most commonly mutated gene in all pulmonary adenocarcinoma is TP53.
Diagnosis
Diagnosis of lung cancer can be suspected based on typical symptoms, especially in someone with a history of smoking. Symptoms such as coughing up blood and unintentional weight loss can speed up further investigation, such as medical imaging.
Imaging
Chest x-rays (radiographs) are often the first imaging tests performed when a person comes with a cough or chest pain, especially in a primary care setting. Chest radiographs can detect lung nodules/masses suggestive of cancer, although sensitivity and specificity are limited.
CT imaging provides a better evaluation of the lung, with higher sensitivity and specificity for lung cancer compared with chest radiographs (although still significant false positive rates). CT also allows for the evaluation of other relevant anatomical structures such as nearby lymph nodes and bone, which may show evidence of metastatic disease spread. Indeed, the US Prevention Services Task Force recommends an annual low-dose CT examination in adults aged 55 to 80 years who have a smoking history of 30 packs per year and is currently smoking or has stopped within the last 15 years, with certain warnings (see Lung-Lung ). cancer screening).
Nuclear medicine imaging, such as PET/CT and bone scan, may also help to diagnose and detect metastatic disease in other parts of the body.
Histopathology
If possible, a biopsy of any lung cancer suspected to be performed to perform a microscopic evaluation of the cells involved.
Lung adenocarcinoma tends to stain the positive mucin because it comes from the lung producing mucin glands. Similar to other adenocarcinomas, if these tumors are well differentiated (low degrees) they will resemble normal glandular structures. Adenocarcinomas with bad differentiation will not resemble normal glands (high levels) and will be detected by seeing that they are stably positive for mucin (which is produced in the gland). Adenocarcinoma can also be distinguished by TTF-1 staining, cell markers for adenocarcinoma.
To reveal the adenocarcinomatous lineage of the solid variant, demonstrations of intracellular mucin production can be performed. The focus of metaplasia and squamous dysplasia may be present in the proximal epithelium to adenocarcinoma, but this is not a precursor lesion for this tumor. In contrast, peripheral adenocarcinoma precursors have been called atypical adenomatous hyperplasia (AAH). Microscopically, AAH is the focus of good demarcation of epithelial proliferation, containing cuboid cells into low columnar cells that resemble club cells or type II pneumocytes. It shows different levels of cytologic atypia, including hypercromasia, pleomorphism, prominent nucleolus. However, atypia is not limited as seen in adenocarcinoma. AAH lesions are monoclonal, and they share many molecular aberrations (such as KRAS mutations) associated with adenocarcinoma.
Classification
The category of adenocarcinoma includes various subtypes, and each tumor tends to be heterogeneous in composition. Several major subtypes are currently recognized by the World Health Organization (WHO) and the International Association for the Study of Lung Cancer (IASLC)/American Thoracic Society (ATS)/European Respiratory Society (ERS):
- Noninvasive or minimally invasive adenocarcinoma
- Adenocarcinoma in situ lung (Bronchioalveolar carcinoma)
- Minimally invasive lung adenocarcinoma
- Invasive adenocarcinoma
- Dominant dominant adenocarcinoma
- Papen dominant adenocarcinoma
- Micropapillary predominant adenocarcinoma
- Adenocarcinomas are dominantly solid
- Invasive mucinous adenocarcinoma
As many as 80% of these tumors, more than one subtype component will be recognized. Resected tumor surgery should be classified with a comprehensive histologic subtype, describing the pattern of involvement with a 5% increase. The dominant histologic subtypes are then used to classify the tumor as a whole. The dominating subtype is prognostic for survival after complete resection.
Seat rings and clear cell adenocarcinomas are no longer histologic subtypes, but cytological features that can occur in tumor cells of several histologic subtypes, the most commonly dense adenocarcinoma.
Some variants are not clearly recognized by the WHO and IASLC/ATS/ERS classifications:
- lung enterenocarcinoma
- Cribriform lung adenocarcinoma
Management
Adenocarcinoma is a non-small cell lung carcinoma, and therefore, unresponsive to radiation therapy such as small cell lung carcinoma, but rather treated surgically, for example with pneumonectomy or lobectomy. Early disease is treated with surgery. Targeted therapy is available for lung adenocarcinoma with specific mutations. Crizotinib is effective in tumors with fusion involving ALK or ROS1, whereas gefitinib, erlotinib, and afatinib are used in patients whose tumors have mutations in EGFR.
Epidemiology
The incidence of pulmonary adenocarcinoma has increased in many advanced Western countries in recent decades, where it has been the most common type of lung cancer in both smokers (replacing squamous cell lung carcinoma) and non-smokers for life (<100 stems in a lifetime).
Nearly 40% of lung cancers in the US are adenocarcinoma. Most cases are associated with smoking.
References
Source of the article : Wikipedia
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