Bald spot on ear, turned histeocytoma? changed into something else?

I have a 5yr old lab basset hound mix who developed a small circular hairless spot on her ear, approx 1.5cm in diameter.  It persisted for about a month and then we took her swimming, and over night the spot became inflamed and became a bump.  We took her to the vet and they thought it was ring worm and gave us some lotion that was supposed to fix it in 4-6 weeks.  The lotion was ineffective.  We came back and got a second opinion, they said its actually a histeocytoma, as it looked just like one

http://vetmedicine.about.com/od/diseasesconditionsfaqs/f/FAQ_histiocytom.htm

just like the picture there.

We thought ok should be fine, and should go away eventually.  But now about 2 weeks later it has changed color and developed a yellowish white crust(see attached pictures).  The vet thinks we should have a $400 procedure to get it removed and tested, but we don't have that kind of cash, so I thought I would appeal to the internet and see if anyone has any ideas.

There also appears to be something leaking from it that is causing the hair around it to become plastered to the bump.  I havent seen any pus or liquid, I have just found her hair stuck to the bump with something that looks like hardened pus.

Does anyone have any ideas?

[Ghilly]

The first thing it looked like to me was ringworm, but if it wasn't responding to any antifungals then it's time to move on to another diagnosis.  Histiocytoma would have been my next guess, although it doesn't look QUITE as domed-up as histiocytoma usually does.  It appears to flatter and less red than histiocytoma.

How did they determine that it wasn't a fungal-type thing?  Did they culture it or was it simply decided that it wasn't fungal because it didn't respond to the ringworm medication?  I would seek yet another opinion and ask the vet to do a skin scraping of the lesion.  That crusty stuff, to me, looks like it COULD still have something to do with some type of skin parasite.  Although histiocytoma CAN look similar to this, it's just a case of it looking a bit different than it usually does.  And if it IS histiocytoma, these traditionally never metastasize, so unless it becomes something that gives the dog a lot of trouble, I would just leave it alone.

Yes, I think my next move, if I were you, would be a third opinion from another vet and possibly a skin scraping to culture the lesion, and then take it from there.  Please let us know how things go and what you decide on.

Ghilly