Bronchioloalveolar carcinoma

Bronchioloalveolar carcinoma is one of the forms of lung cancer and, although rare, is the most common form that occurs in patients who have never smoked in their lives, in women, and in Asians.. Bronchioloalveolar carcinoma is defined as carcinoma in situ, that is, it is not an invasive or metastatic tumor and originates, as its name suggests, in a fairly peripheral area of the lung parenchyma, the bronchoalveolar terminal region. Although it does not invade other tissues, bronchioloalveolar carcinoma is a malignant and frequently fatal tumor. Surgery, either a lobectomy or pneumonectomy, is usually recommended to control the tumor, although recurrences are common. Mixed tumors are frequently seen, that is, with adenocarcinoma characteristics together with purely bronchiolopulmonary characteristics.

Classification

Bronchioloalveolar carcinoma is classified by oncologists as a non-invasive tumor and is considered a subtype of lung adenocarcinoma. Despite this, it is distinguished from other adenocarcinomas by its clinical characteristics, its prognosis, and the response of patients to treatment. Bronchioloalveolar carcinoma is subdivided into four classes based on location: intraparenchymal, parietal, pericardial, apical, and peridiaphramatic bronchioloalveolar carcinomas; this division will determine a different therapeutic approach and a different prognosis.

Epidemiology

Bronchioloalveolar carcinoma represents 5% of non-small cell lung cancers. Approximately 30% of patients with bronchioloalveolar carcinoma have never smoked and more than half of the cases are women. The prognosis improves with the higher proportion of bronchioloalveolar elements in the tumor, that is, a pure bronchioloalveolar carcinoma has better than a tumor. mixed and this in turn better prognosis than a pure adenocarcinoma.

Diagnosis

In the chest X-ray it appears multicentric in one or both lung fields, even when there has been no distant metastasis, adopting a nodular or diffuse reticulated morphology. It looks like pneumonia, as various nodules coalesce with pulmonary infiltrates and an air bronchogram (together with primitive lung lymphoma, these are the only neoplasms that produce it). Since it does not affect important bronchi, there is usually no associated atelectasis or emphysema.

Pathology

They are not as hard in consistency as other carcinomas. The nodules have a translucent grayish appearance when there is a mucinous discharge; otherwise they are solid whitish-grey areas, which can be confused with pneumonia on superficial inspection. Bronchioloalveolar carcinoma originates from alveolar cells, possibly type II pneumocytes. It seems that it has a reaction with a certain type of virus (paramyxovirus). The lesions are very similar to those of an apparently infectious disease of sheep in South Africa. However, numerous efforts to identify an infectious agent in man or to transmit the disease to sheep with cell-free extracts of human carcinoma have failed.

Histology

It is a variety of adenocarcinoma, a tumor that covers the alveoli and bronchioles, covering their lumen, generally not affecting the bronchi. The cells are columnar or tall cuboidal, with the occasional presence of cilia, which line the alveolar septa, in numerous branched papillary formations. Tumor cells frequently contain abundant mucinous secretion. The degree of anaplasia is highly variable, but in general they are well-differentiated tumors that tend to respect the original septal architecture. Ultrastructurally, bronchoalveolar carcinomas are a heterogeneous group, formed by bronchiolar mucus-secreting cells, Clara cells, or rarely type II pneumocytes. All of them are recognizable by immunohistochemistry due to the presence of positive Enolase V-2 in Clara cells and because they express the transcription factors C-myc32 and CycD8. Paracrine secretion of FGF-1 by clear cells will indicate a much worse prognosis.

Clinical picture

It generally presents with impaired oxygen transfer, respiratory failure, dyspnea, hypoxemia, and production of large amounts of mucus (productive cough). It can even produce hydroelectrolytic alterations. It is the histological type most related to women with scleroderma. It is also frequently associated with positive rheumatoid factor in general.

Forecast

Whenever they present as single lesions, it is better than the rest of the bronchial carcinomas, since it has little tendency to invade neighboring tissues and to the appearance of distant metastases, either through the blood or the lymphatics. Therefore, it has exclusively pulmonary growth. It usually leads to the death of the patient as it is multifocal; but the chances of survival increase markedly when it occurs in the left lung. In the event that the lung secretes FGF-1, surgical treatment will be ruled out from the outset; if the tumor does not express this growth factor, surgery may be considered, although it only improves survival in 40% of individuals.