Tonight I noticed something slightly amiss with my neutered male's
rear.  Nothing major, just more 'obvious' somehow. I checked and see
there was some rawness to the side of the anus.
I thought to myself "ok" maybe just some odd injury, etc.  But when
checking further, there's a largeish hard mass basically on the side of
the tail base.  Inside.  I'd say it's the size of a walnut or a
elongated ping pong ball?    I saw a tiny droplet of white pus? come
out where I 'think' the anal gland hole is.

I've had indoor cats all my life, mostly purebred (and obsessed with
their health) and I have to say, I've NEVER had a cat with any
semblance of an anal gland issue.  Nor have any of my cat friends or
breeder acquaintances.   But I latched onto that so I don't panic.
I've been googling and can't find any mention of WHERE (inside or
protruding out) or how BIG these anal gland abseses can get.

I'm worried he has a tumor.  Clearly this mass is very close to the
exterior but the size is frightening.   He appears fine.  Bright-eyed,
eating/drinking.  I left a message with the vet and plan on bringing
him in tomorrow ASAP.

Any ideas?  :(