McKenna was the misdiagnosed cancer patient in the Season 4 episode Games. He was portrayed by actor Matt DeCaro.
James Wilson tells Gregory House about McKenna. Although he seemed to have cancer, a review of his biopsy results showed the original biopsy was a false positive. Wilson was inviting McKenna in to give him the good news, but House didn't seem to care.
However, when McKenna arrives, House comes into Wilson's office too - wearing an atypical lab coat. Wilson can't figure out why House is there, but when he gives the good news to McKenna, he's shocked. House doesn't seem to be surprised by his reaction. McKenna complains that he's already had three goodbye parties, he had planned to go to Venice, and he's sold his house and owes his broker $6,000. Wilson tells him that he can still go to Venice, but when McKenna walks off after a terse thank you, Wilson is astounded.
House explains that cancer made the patient special, probably for the first time in his life. Having the diagnosis taken away made him ordinary again.
However, House learns that Wilson is planning to pay McKenna's lost commission. He reminds Wilson it wasn't his fault that McKenna was misdiagnosed.
Wilson invites McKenna in and offers him a $6,000 check. McKenna takes it, rips it up and tells Wilson he's going to be looking for a lot more money.
Wilson figures out House got to McKenna and convinced him that he should sue Wilson for malpractice despite the fact that McKenna hasn't suffered any damages. House assures Wilson he only did it so Wilson would have money just in case House had to borrow some.