Q:

"The group looked at tissue from people who had any of five diagnoses" - why isn't there "the" before "five diagnoses"?

From a news report:

The group looked at tissue from people who had any of five diagnoses: autism-like conditions, schizophrenia, bipolar disorder, depression and alcoholism.

Why isn't there a definite article before "five diagnoses"? They are listed, so it's a definite word. I would have used the:

The group looked at tissue from people who had any of the five diagnoses: autism-like conditions, schizophrenia, bipolar disorder, depression and alcoholism.'

A:

The group looked at tissue from people who had 
any of these five diagnoses: ...
any of five diagnoses ... 
any of the five diagnoses
these five diagnoses = focus your attention, listener, on this list of five diagnoses I am about to enumerate
five diagnoses  =  five diagnoses were involved...
the five diagnoses =  listener, I'm speaking of the five diagnoses with which you are familiar or have already heard about (or which I intend to make my topic)

