A local research team has confirmed that the thymic epithelial tumor, a rare chest cancer, is increasing in Korea.

The research team, led by Professors Jung kyu-won at the National Cancer Center and Shin Dong-wook and Jo Jung-ho at Samsung Medical Center, concluded after analyzing the data of 5,812 thymic epithelial tumor patients registered with the National Cancer Registry from 1999 to 2017 to determine the occurrence and survival trends.

Thymic epithelial tumors arise in the thymus gland located behind the sternum between the two lungs, and it used to be a very rare cancer that occurred in less than 1 per 100,000 people a year.

The thymus plays an important role in immune function in childhood, but it loses its function in adulthood and gradually decreases and is replaced with adipose tissue. The tumor has two types -- thymoma, which grows slowly and has a good course, and thymic epithelial tumors, which has a poor prognosis.

However, the research team confirmed that thymic epithelial tumors had increased rapidly at an average annual rate of 6.1 percent between 1999 and 2017 -- thymoma by 5.6 percent and thymic cancer by 7 percent.

The research team also analyzed the 5-year net survival rate, the relative survival rate compared to the general population of the same age and sex.

The average net survival rate for thymoma was 82.3 percent, with the survival rate for patients diagnosed with thymoma increasing from 64.3 percent from 1999 to 2002 to 90.6 percent in 2013-2017.

However, the average net survival rate for thymic cancer was 46.2 percent, showing only a small increase from 39.4 to 47.9 percent during the same period.

“Until now, studies on the thymic epithelial tumor, rare cancer, have rarely been published in Asia,” Professor Jung said. “The results of this research will serve as basic data for establishing a monitoring system for diagnosing, treating, and monitoring thymic epithelial tumors, which are on the rise.”

Professor Shin also said, “Although the detection of asymptomatic thymoma is increasing due to the recent generalization of lung cancer screening, we cannot exclude the possibility that thymic epithelial tumor is increasing due to radiation exposure as the number of thymic cancer is also increasing.”

Therefore, further research is required, Shin added.