Anne, take a look at this and read descriptions for when it is not on tip
to see if it fits (I can't tell from your description if this fits.):
http://www.afip.org/ferrets/chordoma.html
 
The spot on the leg may be a benign mast cell tumor (a common ferret
problem).  Unlike dogs there has only been one malignant one documented
in a ferret and that was an internal one.  They can get infected, though,
and should be removed with pathology done by a ferret knowledgeable
pathologist.
 
The fur thinning needs to be watched in case adrenal neoplasia is
starting.
 
Here are sites to help you look up information you need:
http://fhl.sonic-weasel.org
http://www.ferretcongress.org (click open the crit.refs.)
http://listserv.cuny.edu/archives/ferret-search.html
 
***** It is always important whenever possible to learn about health
BEFORE the information is needed because otherwise health problems may
not get the timely care they need and for some needless death may occur;
preferably use a ferret-knowledgeable vet or one who is willing to learn.
When that is lacking check the links to lists of vets at
http://www.ferretcongress.org *****
 
Ticks:
http://www.smartgroups.com/vault/ferrethealth/common_parasites.txt
http://listserv.cuny.edu/archives/ferret-search.html
http://fhl.sonic-weasel.org
[Posted in FML issue 4247]