Tuberculosis (TB) is an infectious disease, not a form of cancer. The two are distinct medical conditions, but confusion can arise because they may present with similar symptoms, particularly when affecting the lungs. They stem from unrelated causes and require entirely different treatment approaches.
Understanding Tuberculosis
Tuberculosis is an infectious disease caused by a specific bacterium, Mycobacterium tuberculosis. This microorganism is spread through the air when an infected person coughs, sneezes, or speaks, releasing tiny droplets containing the bacteria for others to inhale.
While TB is most known for affecting the lungs, a condition called pulmonary tuberculosis, it can also impact other parts of the body like the kidneys, spine, or brain. The body’s immune system fights the bacterial invasion, and in many individuals, the infection can remain dormant, or latent, for years without causing symptoms. Active disease occurs when the immune system can no longer contain the bacteria.
Understanding Cancer
Cancer is a classification of diseases characterized by the uncontrolled division and growth of the body’s own cells. This abnormal growth is triggered by mutations in the genes that regulate the cell cycle. These genetic changes can be inherited or acquired throughout a person’s life due to environmental factors or errors during cell division.
These abnormal cells can form masses of tissue called tumors. Tumors can be benign, meaning they do not invade nearby tissues, or malignant, which is the definition of cancer. Malignant tumors can invade surrounding tissues and spread to distant parts of the body through the bloodstream or lymphatic system in a process called metastasis. Unlike TB, cancer is a non-communicable disease.
Distinguishing Between Symptoms and Diagnosis
A primary source of confusion between tuberculosis and lung cancer is the overlap in their symptoms. Both conditions can cause a persistent cough, unexplained weight loss, fever, fatigue, and night sweats. Both may also lead to coughing up blood, a symptom known as hemoptysis. These shared signs can lead to an initial misdiagnosis, especially in regions where tuberculosis is common.
To differentiate between the two, healthcare professionals rely on distinct diagnostic procedures. For tuberculosis, diagnosis often begins with a tuberculin skin test or a blood test to detect the Mycobacterium tuberculosis bacteria. If these tests are positive, a chest X-ray is typically performed to look for characteristic changes in the lungs. A definitive diagnosis of active TB requires identifying the bacteria in a sample of sputum.
Diagnosing cancer involves a different set of tools. Imaging studies such as CT scans and PET scans can reveal the size and location of tumors and whether they have spread. The conclusive method for diagnosing most cancers is a biopsy, where a small sample of suspicious tissue is removed and examined under a microscope by a pathologist to identify cancerous cells.
The Association Between Tuberculosis and Cancer Risk
While tuberculosis is not cancer, having a history of TB is associated with an increased risk of developing certain cancers, particularly lung cancer. Individuals who have had pulmonary TB have a higher relative risk of getting lung cancer compared to the general population. This risk is not limited to lung cancer, as associations have also been noted with other cancers.
The proposed biological reason for this link is the chronic inflammation and tissue damage caused by the TB infection. The persistent inflammatory response from the immune system can, over many years, lead to changes in the cells of the lungs. This long-term cellular stress and scarring can result in genetic mutations that may lead to cancer.
Having had TB does not guarantee a future cancer diagnosis. Many factors contribute to this risk, including smoking, alcohol consumption, and overall immune status. A past TB infection is one of several factors that can statistically increase a person’s lifetime cancer risk.