Peacekeeper,

It sounds like the docs have done all the tests necessary and made a
diagnosis.  But, you said no treatment?  Not even antibiotics?

A "lump" on the prostate probably means that the doctors found some
irregularity when they felt his prostate through the rectum.  That is a
standard test called a digital rectal exam (DRE).  Such an irregularity
can be caused by many things.   It also possible that ultrasound showed
something that he refers to as a "lump".

If he has an infection, it would be usual to treat it with an
antibiotic.  But in many cases, the prostatitis doesn't respond to
antibiotics.   If it doesn't hurt or interfere with urine flow, it may
not be necessary to treat it.

It sounds as if the doctors were pretty thorough and I assume they must
have done PSA tests.  From what you say, it would be surprising if his
was not elevated.   In a younger man with elevated PSA or an abnormal
DRE, the nest step would be a biopsy.   But in older men, it might not
be warranted.  There is a small risk of infection, and even if they
found prostate cancer, they probably wouldn't recommend treating it.
The reason is that prostate cancer grows very slowly, and an 80 year old
man will probably live out his life normally without being affected by it.

There are many other things which can cause something like that.  One
would be a cyst.  These things don't go away  usually.  If I were you I
wouldn't be specially concerned about it.

Unfortunately, you don't know just what his doctors told him.  They may
have discussed with him the possibility he might have prostate cancer
and the fact that it probably wouldn't need to be treated.  They
certainly should have told him to come back regularly for evaluation
because if he does have prostate cancer and it is more aggressive than
normal, it could cause obstructive and other symptoms.   Even if he
doesn't have prostate cancer, with his symptoms he could develop a
urinary obstruction, and that could be life threatening. Even if he did
have prostate cancer, they would probably treat it with hormone
suppressing drugs to control it rather than using surgery or aggressive
treatment with radiation.  I would be very surprised if they didn't go
into all of this,  but only your father-in-law can tell you.   If you
think either that he is not getting competent medical advice or that he
is ignoring it, you should try to take it up with someone, but I'm not
sure whom.   The important thing is that goes back regularly for
checkups since whatever is wrong with  him could cause serious problems
which can be avoided with treatment.  A neighbor of mine ignored his
prostae problems, and as a result both his kidneys failed.  He doesn't
have prostate cancer, but he needs dialysis several times a week.
Perhaps you can tell him that you have found that in a sense prostate
cancer in a man his age is almost normal and not very frightening.  But
keeping track of just what is going on with his prostate is important to
avoid serious problems.