The Thymus Gland: More Important Than Previously Thought

There’s a small fatty gland, nestled behind the sternum, often dismissed as ‘useless’ in adults. But recent research indicates that the thymus gland might be more essential than experts initially believed.

Although there’s some disagreement among scientists about its significance, a 2023 study conducted in the US found that individuals who have their thymus removed are at a higher risk of dying from various causes within five years post-surgery. There’s also an increased likelihood of developing cancer during this timeframe.

“We discovered that the thymus is absolutely required for health. If it’s not there, the risk of dying and the risk of cancer is at least double,” said Harvard University oncologist David Scadden following the research publication.

The study was purely observational, which means it couldn’t definitively establish a causal link between thymus removal and the onset of cancer or other fatal conditions. Still, researchers view the findings with concern. They argue that preserving the thymus “should be a clinical priority” when possible.

In childhood, the thymus is critical for immune system development. Children who have their thymus removed at a young age experience long-term reductions in T cells—these are the white blood cells that fight off germs and diseases. Furthermore, kids without a thymus often have a weakened immune response to vaccines.

However, by the time a person reaches puberty, the thymus shrinks, producing fewer T cells, making its removal less immediately harmful. Due to its position in front of the heart, it’s often taken out during cardiothoracic surgeries.

Yet, for some patients with thymus cancer or chronic autoimmune diseases, a thymectomy—surgical removal of the thymus—may be necessary. Interestingly, it might also be quite beneficial.

In a study that involved over 6,000 patients who underwent cardiothoracic surgeries, researchers compared those who kept their thymus to 1,146 who had it removed. The results revealed that those who had a thymectomy were nearly twice as likely to die within five years, even after controlling for variables like sex, age, race, and pre-existing conditions.

Additionally, patients without their thymus were also twice as likely to develop cancer within five years post-surgery. The cancer that developed in these patients was generally more aggressive and had a higher tendency to recur after treatment compared to those who hadn’t undergone thymectomy.

“This indicates that the consequences of thymus removal should be carefully considered when contemplating thymectomy,” Scadden stated.

While the reasons for these associations remain unclear, researchers suspect that the lack of a thymus may disrupt healthy immune function in adults. Some patients who had undergone thymectomy exhibited less diversity in their T-cell receptors, which could potentially lead to the development of cancer or autoimmune diseases after surgery.

Collectively, these findings suggest a critical role for the thymus in producing new T cells in adulthood and maintaining overall health.

However, the discourse doesn’t end there. A subsequent study published in 2025 by Yale School of Medicine researchers aimed to verify Scadden’s findings by analyzing patient records from 2004 to 2022 in national databases.

Interestingly, the Yale study could not find significant evidence that removing the thymus adversely affected patient health. Their results indicate that there’s still much to uncover regarding the implications of thymus removal.

“Thymectomy in adults with small or localized thymomas was not associated with increased five-year mortality or cancer death,” the researchers noted.

In conclusion, the long-term results and specific immunological outcomes regarding thymus removal deserve further investigation. The earlier study by Scadden was published in The New England Journal of Medicine.