Content Reviewers:Antonella Melani, MD, Lisa Miklush, PhD, RNC, CNS, Ashley Mauldin MSN, APRN, FNP-BC
Lung cancer is a malignant tumor that primarily originates in the lungs, or less frequently can originate in another organ and spread to the lungs through metastasis. Unfortunately, lung cancer is one of the most common and aggressive types of cancer.
Alright, now the lungs are these paired organs in the chest containing a collection of tubes and passages called the airways, which include the bronchi, then the bronchioles, the alveolar ducts, and finally the alveoli. The airways are lined by several types of epithelial cells that serve multiple functions.
These include columnar epithelial cells that have hair-like projections called cilia, which work to sweep foreign particles and pathogens up and out of the airways. Another type, called goblet cells, secrete mucin to moisten the airways and trap foreign pathogens. There are also club cells, sometimes called Clara cells, that secrete glycosaminoglycans to protect the bronchioles, and neuroendocrine cells that secrete hormones into the blood.
So, lung cancer occurs when any of these epithelial cells acquire mutations, which can arise due to a variety of risk factors. Environmental risk factors include exposure to toxins like tobacco smoke, air pollution, asbestos, coal dust, radon gas, or ionizing radiation. There are also some genetic risk factors, where few clients are genetically predisposed to develop lung cancer even without the presence of environmental risk factors.
So, once an epithelial cell becomes mutated and cancerous, it starts dividing uncontrollably, forming a tumor mass. As the tumor keeps growing, new blood vessels also develop via angiogenesis to supply it. Eventually, cancerous cells start invading neighboring tissues, and may even spread to nearby lymph nodes or metastasize to distant organs, such as the brain, bones, or liver.
Now, there are two main types of lung cancer, non-small cell and small cell. Non-small cell lung cancers account for most lung cancers, and there’s different subtypes depending on the cell of origin. The most common one is adenocarcinoma, which usually develops at the periphery of the lung from the goblet cells; another quite common one is squamous cell carcinoma, which is usually centrally located in the lungs, and originates from mutated columnar epithelial cells that become squamous epithelial cells.
Now, the clinical manifestations of lung cancer vary based on the size and location of the tumor, and whether or not it secretes hormones. Initially, clients can be completely asymptomatic. Over time, the body mounts an immune response to fight the tumor off, so clients may start experiencing unintentional weight loss, fever, malaise, and night sweats. If the tumor grows enough to physically obstruct the airway, it can cause dyspnea, wheezing, and persistent cough.
If tumor necrosis occurs or if cancer cells invade a blood vessel, individuals can experience hemoptysis; while compression of nearby nerves can cause hoarseness and pain.
Tumors that arise at the apex of the lungs are called Pancoast tumors, and can push up against blood vessels and nerves located in the region. Compressing major blood vessels like the superior vena cava can prevent blood from draining from the head, leading to facial swelling or puffiness; while compressing the brachial plexus can cause shooting arm pain and weakness; and the cervical sympathetic chain can result in Horner syndrome, which presents with ptosis, miosis, and facial anhidrosis.
Additionally, some tumors might be able to inappropriately secrete hormones, so the client may develop a paraneoplastic syndrome. Squamous cells in lung cancers sometimes secrete parathyroid hormone related peptide, or PTHrP, which mimics parathyroid hormone or PTH, causing hypercalcemia, fatigue, and muscle weakness.
On the other hand, small cell lung cancers may secrete antidiuretic hormone or ADH for short, as well as adrenocorticotropic hormone or ACTH. ADH secretion can lead to syndrome of inappropriate antidiuretic hormone secretion or SIADH for short, which results in hyponatremia and reduced urine output; while ACTH secretion results in Cushing syndrome, with symptoms like hyperglycemia, hypertension, skin hyperpigmentation, osteoporosis, weight gain, easy bruising, and frequent infections from a weakened immune system. Lastly, small cell lung cancers can also cause the production of antibodies against the neuromuscular junction, which results in Lambert-Eaton syndrome, causing muscle weakness.
Diagnosis of lung cancer involves history and physical assessment, as well as additional diagnostic tests like imaging. In most cases, chest X-rays show a parenchymal lesion like a poorly defined nodule, called a coin lesion; while CT scan can be used to stage the tumor by defining the location, and look for lymph node involvement or metastasis. Once a suspicious lesion is found on imaging, a biopsy is needed to confirm the diagnosis.
Treatment for lung cancer depends on its aggressiveness and extension. Small, localized tumors can be treated with partial resection, which is when the affected lung area is surgically removed. On the other hand, clients with larger tumors may require lobectomy, or removal of the lung lobe containing the tumor, and even pneumonectomy, or surgical removal of the entire lung. Also, any involved nearby lymph nodes should be resected.
In addition to surgery, clients could be treated with chemotherapy, immunotherapy, or radiotherapy. Finally, metastatic lung cancers can’t be surgically resected, so they are often treated with a combination of therapies, as well as palliative care to decrease their symptoms and improve quality of life.