Solder made the announcement at a charity event this week for the Joe Andruzzi Foundation, according to ESPN. He and his wife reportedly wanted to draw attention to the rare cancer called a Wilms' tumor, which primarily affects young children under age 5.
Solder posted a picture on Twitter of his son Hudson being treated at the hospital to thank supporters.
The Wilms' tumor is an extremely rare cancer that affects just 500 children every year in the U.S., according to Dr. Johnathan Ross, chief of pediatric urology at University Hospitals Rainbow Babies & Children’s Hospital.
"It looks different than kidney cancer in adults," said Ross, who has not worked with Hudson. "One of the good things about Wilms' tumors ... they’re much more sensitive to chemotherapy and radiation" compared to adult cancer.
Most Wilms' tumors respond well to treatment, Ross said, noting that removing the affected kidney and following with chemotherapy or radiation is a common form of treatment. Ross explained that the tumor often does not make children feel sick or ill, so they usually are diagnosed after a parent or doctor sees or feels the tumor in the abdomen.
"They usually don’t come in until it's large enough that their belly is distended," Ross explained.
Though Soder was previously diagnosed with testicular cancer, Ross said there's no known link between testicular and Wilms' tumor in families.