Lump on my dog...

Question
Hello, my female German Shepherd is 2 and she has a lump on her side.  There was something black protruding from this top of the lump so I began to further investigate.  When I began to squeeze the lump a white substance came out that was about 1 inch long and nearly 1/8 inch in diameter. this is the second one of these in 2 months.  What could it be, and what should I do?  

Answer
It sounds like you dog might have a sebaceous cyst or she could have a Cuterebra grub in her side.
You might want to look at this case of a Cuterebra in a cat:

http://www.peteducation.com/article.cfm?c=0+1540&aid=3327

However, since you got some white, cheesy stuff out of it the chances are better that it's a sebaceous cyst.

Either way, the vet needs to see it. A cyst will need to be removed via a small surgery because it will keep coming back.

A cuterebra larvae infection also needs to be removed by the vet. The surgery site will be small and the dog will recover with no issues.

But you need to get her into the vets next week. Do not squeeze it anymore as you can make it infected by doing so.