As reported by multiple agencies, Gowans will undergo surgery on the afflicted gland and is predicted to make a full recovery due to early detection.
While the former North Melbourne head coach is said to have displayed no outward symptoms during a recent GP visit, Gowans' prostate issue was first picked up on when being screened for a separate issue.
Speaking ahead of the Easter weekend, Gowans stressed that for men of a certain age, regular prostate check-ups "could save their lives".
“If there's one positive to take from this it's that the tumour can be removed and hasn't spread, which may not have been the case if it wasn't discovered so early,” Gowans said.
“I'm extremely lucky that my doctor pushed for further investigation into something that wasn't quite right – I didn't have any symptoms and I was otherwise feeling OK.
“What I hadn't done was have a check-up for prostate cancer, so if there's one message to come from this experience it's to get checked, and urge your loved ones to get checked, because it could save their life.”
Premiership Swan and current assistant Nick Davis will take the reins in Gowans' absence.
The Swans will be looking to break their duck in 2023 after going winless throughout their debut season.