Adenocarcinoma of lung

Overview

Adenocarcinoma of the lung (pulmonary adenocarcinoma) is a common histological form of lung cancer that contains certain distinct malignant tissue architectural, cytological, or molecular features, including gland and/or duct formation and/or production of significant amounts of mucus.

It occurs due to abnormal and uncontrolled cell growth in the lungs. It is a subtype of non-small cell lung cancer that is often diagnosed in an outer area of the lung. Early lung cancers may not be associated with any signs and symptoms. As the condition progresses, affected people can experience chest pain, a persistent cough, fatigue, coughing up blood, loss of appetite, unexplained weight loss, shortness of breath, and/or wheezing.

It is one of the most common forms of cancer that affects adults in the United States, can be classified broadly into small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). The latter variety can be further classified into adenocarcinoma, squamous cell and large cell varieties. Conceptually, the difference between SCLC and NSCLC is the approach that is taken in both performing the diagnostic workup and the treatment planning. SCLC tends to be widely disseminated at its first presentation, thus favoring the use of chemotherapy as the mainstay of treatment. NSCLC, on the other hand, may be localized to the lung at the time of first presentation, favoring the use of surgical resection with or without radiation therapy as the initial mainstay of treatment.

Symptoms

  • Cough
  • Coughing up blood
  • Wheezing
  • Shortness of breath
  • Discomfort during breathing
  • Chest pain
  • Fever and a mucus-producing cough
  • Discomfort during swallowing
  • Hoarseness
  • Weight loss and poor appetite
  • Other symptoms, if cancer has spread to the brain, bones or elsewhere
  • Certain types of lung cancer can also cause unusual growth of the fingers, called clubbing, in which the outer portions of the fingers look like little clubs

Causes

The underlying cause of lung adenocarcinoma is generally unknown; however, risk factors for developing a lung cancer include smoking; exposure to secondhand smoke and other toxic chemicals; a family history of lung cancer; previous radiation treatment to the chest or breast; and HIV infection.

Most cases of adenocarcinoma are associated with smoking; however, among people who have smoked fewer than 100 cigarettes in their lifetimes ("never-smokers"), adenocarcinoma is the most common form of lung cancer. Its incidence has been increasing in many developed Western nations in the past few decades, where it has become the most common major type of lung cancer in smokers (replacing squamous cell lung carcinoma) and in lifelong nonsmokers. According to the Nurses' Health Study, the risk of adenocarcinoma of the lung increases substantially after a long duration of previous tobacco smoking, with a previous smoking duration of 30 to 40 years giving a relative risk of approximately 2.4 compared to never-smokers, and a duration of more than 40 years giving a relative risk of approximately 5.

Diagnosis

  • To confirm the diagnosis, a chest X-ray to see if there are any masses that could be cancer.
  • If the X-ray shows anything suspicious, a computed tomography (CT) scan will be done to confirm the size and location of any mass or tumor.
  • If cancer is suspected, further tests will be done to make the diagnosis, establish the specific type of lung cancer and determine how far it has spread. 

Treatment

Treatment varies based on the severity of the condition, the associated signs and symptoms and the affected person's overall health. It may include a combination of surgery, radiation therapy, chemotherapy, targeted therapy, and/or watchful waiting.

Targeted therapy is available for lung adenocarcinomas with certain mutations. Crizotinib is effective in tumors with fusions involving ALK or ROS1, whereas gefitinib, erlotinib, and afatinib are used in patients whose tumors have mutations in EGFR.

Also, surgery is the main treatment for all NSCL cancers if the cancer is contained in the chest and has no evidence of having spread to areas outside the chest. Three types of surgery can be used:

  • Wedge resection: Removal of only a small part of the lung
  • Lobectomy: Removal of one lobe of the lung
  • Pneumonectomy: Removal of the entire lung
  • VATS (Video-assisted thoracoscopy): In this procedure, which can be both diagnostic and therapeutic, the surgeon places a flexible tube into an incision in the chest and can visually inspect the surrounding surfaces of the inner and outer linings of the lung area and even do surgery to remove abnormal areas. It is a less-invasive procedure compared to a larger operation, called a thoracotomy.

Resources

  • NIH