ESSENDON club doctor Bruce Reid will be on leave from the club indefinitely after being diagnosed with cancer.

Reid, who has been at the Bombers for more than 36 years, has undergone surgery and is recovering in hospital.

The cancer has been identified as mesothelioma which affects mesothelial cells across internal organs.

"Reidy's health and wellbeing are our No.1 priority during this difficult time," Essendon chief executive Xavier Campbell said.

"He knows he has the full support of the entire Essendon family and the club will continue to do everything we can to support Bruce, his wife Judy and their five children."

Reid was part of Essendon's medical team during the supplements saga of 2012, with the AFL dropping all individual charges against him in September 2013.