My sister worked in urology. She could smell bladder cancer. She would collect the sample, catch a whiff, recognize the sharp scent, and then confirmation from the lab. She never told patients, but she would tell the doctor, "that one has cancer." It is wild that she can do that; they have dogs that do it.

Similarly, a human smell factoid is humans are more sensitive to the smell of petrichor (fresh rain on a dry area) than sharks are to blood!