Cardiff City announced that the defender is being treated for cancer.
The Ivory Coast international has been diagnosed with Non-Hodgkin lymphoma and is undergoing chemotherapy.
“Sol has begun his battle in typically positive spirits and will continue to be an integral part of the Bluebirds family,” the club statement said.
The club’s statement added: “During treatment Sol will support his team mates at matches and younger players within the Academy, with whom he will continue his coaching development.
“While we request privacy for him and his family at this time, messages of support to be passed on to Sol may be sent to firstname.lastname@example.org.”
“We are all with you Sol.”
The National Health Service Wales describes the illness as “a type of cancer that develops in the lymphatic system, a network of vessels and glands spread throughout your body.