My coworker has a pilonidal cyst

WARNING: DO NOT IDLY GOOGLE. WHAT CAN BE SEEN CANNOT BE UN-SEEN. THIS MAY CAUSE PSYCHOLOGICAL HARM AND/OR INVOLUNTARY EYE-BLEACHING. DO NOT GOOGLE.

I had one all through high school and only learned what was going on after I graduated. It has a particular odor, and I know from experience that it is extremely itchy. All the symptoms went away after a rather minor outpatient surgery.

I was super embarrassed when I had mine, I didn't know where the smell came from and my hygiene was excellent. I wished someone had told me years earlier so that I didn't have to feel that way through all of high school.

How do I bring it up to my coworker? We're pretty chill, I've worked with him nearly every day for two years, but I'm not sure how to say, "hey, that smelly thing you're hoping I can't smell is a cyst".