ALK and ROS fusions offer opportunities for targeted therapies with tyrosine kinase inhibitors. Pathophysiology
The respiratory tract can be divided into two main components: the conducting airways and the gas exchange airways. The gas exchange airways are made of alveoli, small microscopic air sacs that are responsible for the exchange of oxygen and carbon dioxide during normal breathing. Alveoli are composed of two cell types, type I and type II pneumocytes. Type I pneumocytes cover 95% of alveolar surfaces, and are not able to regenerate. Type II pneumocytes are more common, making up 60% of the cells within alveolar epithelium, but constitute only 3% of the alveolar surface.There are several factors that contribute to the transformation of normal alveolar epithelium into dysplastic, or pre-cancerous, lesions. Adenocarcinoma of the lung develops in a step-wise progression as type II pneumocytes undergo consecutive molecular changes that disrupt normal cell regulation and turnover. Atypical adenomatous hyperplasia (AAH) is considered a pre-cancerous lesion, and is thought to further progress to adenocarcinoma in situ and invasive adenocarcinoma of the lung. The lesions of AAH are <5 mm, can be single or multiple, and have a ground glass appearance on CT imaging. As more genetic mutations and dysregulation of normal cell signaling pathways accumulate, AAH can progress to adenocarcinoma in situ (AIS). AIS lesions are classified as small tumors <3 cm with abnormal type II pneumocyte cell growth that is limited to the alveolar spaces i.e. without invasion into the stroma, pleura, or vasculature.
An amniotic fluid embolism (AFE) is a very uncommon childbirth (obstetric) emergency in which amniotic fluid enters the blood stream of the mother, triggering a serious reaction, which results in cardiorespiratory (heart and lung) collapse and massive bleeding (coagulopathy). The rate at which it occurs is 1 instance per 20,000 births and it comprises 10% of all maternal deaths. This condition is unpredictable and no risk factors have been verified. Signs and symptoms
Amniotic fluid embolism is suspected when a woman giving birth experiences very sudden insufficient oxygen to body tissues, low blood pressure, and profuse bleeding due to defects in blood coagulation. Though symptoms and signs can be profound, they also can be entirely absent. There is much variation in how each instance progresses. Causes
AFE is very rare and complex. The disorder occurs during the last stages of labor when amniotic fluid enters the circulatory system of the mother via tears in the placental membrane or uterine vein rupture. Upon later analysis, fetal cells are found in the maternal circulation. When the fetal cells and amniotic fluid enter the bloodstream, reactions occur that cause severe changes in the mechanisms that affect blood clotting. Disseminated intravascular coagulation occurs and results in serious bleeding. The condition can also develop after elective abortion, amniocentesis, cesarean delivery, or trauma. Small lacerations in the lower reproductive tract are associated with AFE.According to one study, induction of labor may double the risk of AFE. However, other studies have refuted this claim.