Underneath the skin: tattoos linked to cancer risk

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Tattooing is a tradition that has stood the test of time. In fact, historians have dated the first evidence of tattoos on human skin back to the neolithic period over 5000 years ago. However, a recent study from Lund University suggests that people with tattoos are at an increased risk of developing an aggressive type of cancer known as lymphoma. So, anyone considering adorning their skin with some fresh ink may need to think twice about the risks associated with tattoos.

Lymphoma is a type of blood cancer that develops in the lymphatic system. Blood continuously travels around the entire body to deliver nutrients to tissues, remove waste products and transport immune cells to sites of infection or injury. When nutrient-, oxygen-rich blood reaches organs and tissues, the high pressure of the blood forces important molecules needed for normal cellular function (plus any other small substances carried in the blood) to be pushed out of the capillary. The combination of molecules that move out of the capillaries is collectively known as tissue fluid. Cells can exchange the useful nutrients and oxygen in the tissue fluid for waste products and carbon dioxide. The majority of tissue fluid is returned back to the capillaries so waste products can be cleared from tissues, but the remaining tissue fluid is drained into a network of small vessels known as the lymphatic system.

Tissue fluid contains a snapshot profile of what is being carried around the body in the blood, therefore, the lymphatic system plays an important role in detecting any deleterious pathogens or cancer cells that are being carried around the body. Usually, a special type of immune cell, called a lymphocyte, detects the pathogens and cancer cells so an immune response can be triggered. However, in lymphoma cancers the lymphocytes acquire genetic mutations that cause them to uncontrollably multiply meaning they do not have time to mature normally, which means they cannot fulfill their normal role in the immune response. 

The cells that usually attack cancer cells become cancerous themselves

Tattoo inks are a complex cocktail of colour pigments and can contain heavy metals such as arsenic, mercury and lead. The process of repeatedly piercing the skin to inject the tattoo ink leads to a local immune response. The ink is transported to the lymph nodes of the lymphatic system where lymphocytes can decide whether to trigger an immune response or not. Concerningly, many of the chemicals in tattoo ink are known carcinogens which means that carcinogenic substances can be transported systemically in the lymphatic system once tattoo ink is injected. These carcinogenic chemicals could cause DNA mutations in a various cells and tissues across the body, including all-important lymphocytes.

Although tattoo inks are known to contain carcinogenic materials, previous studies have not found a significant link between cancer prevalence and tattoos. Yet, a recent study published by scientists from Lund University in Sweden in June 2024 proved otherwise. In their retrospective, case-controlled study, the investigators looked at a population of 1398 people with lymphoma and 4193 controls that did not have lymphoma. After adjusting for other confounding risk factors for cancer such as smoking and hazardous occupation, it was calculated that individuals with tattoos had a 21% higher risk of developing lymphoma compared to non-tattooed individuals. Intuitively, it could be assumed that greater exposure to tattoo ink chemicals from having multiple and/or large tattoos would be linked to a greater risk of lymphoma. However, investigators in this study did not find any correlation between the surface area of tattooed skin and lymphoma risk.

Individuals with tattoos had a 21% higher risk of developing lymphoma compared to non-tattooed individuals

So, should we avoid getting tattoos? There is no simple answer to this. It should be noted that carcinogenesis is a complicated process and the study discussed previously does not prove that tattoo ink directly causes cancer. Yet, the study raises the alarm that there could be an association between tattoos and lymphoma. Most people get their first tattoo at a young age and consequently have a lifetime of exposure to potentially carcinogenic tattoo ink. Therefore, additional research must take place to help decipher this potential link. Further epidemiological studies investigating larger cohorts over longer time periods are needed alongside molecular studies examining the transport of tattoo inks away from the original injection site and the mode of action of the ink chemicals once they reach lymphocytes. Lastly, tattoo ink manufacturers must reduce the number of carcinogens in their products and clearly label potential risks.

Image: Tony Alter via Flickr

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