I was reading up on the etiology and prevalence of a certain hematologic disorder. The prevalence of this disorder was 1 in 200,000 --- but yet, I read that the disorder is 'common'. How exactly is this common when statistically speaking, 5 people per million get diagnosed? I also researched about a certain rare, aggressive stomach cancer where the prevalence was 1 in 50, and the doctor I talked to said it was very rare. I did not question the Doctor, because duh he knows more than I do and I'm just trying to get into medical school---but I am just looking for clarification.