My dog Chloe just celebrated her 6 month ampuversary.  Her fur STILL HASN'T completely grown back yet and she is what I would consider a short haired breed!!!! All of her undercoat has grown in, but her guard hairs are still missing. Right now it looks like she has a tan line (since she is a golden/brown color).

I haven't taken a picture of her rump lately, but I took this video about a week ago. You can see a light spot where her leg used to be because her fur hasn't grown back completely.

-Chloe's mom

It took about 8 months for all of Dakota's hair to grow back and then it was a lighter shade of brown!  His doc said for us to "aggravate" the hair follicles at least once a day by brushing over the bald area (being careful over the actual incision) and that eventually the follicles would wake up again.  They did.  If you live in a sunny environment, be sure to spray some sunscreen on the bald spot if your baby is going to be outside for long.

Dante lost his left front leg due to things other than Cancer as well. 

He'll be celebrating his one year ampuversary in 19 days – and he hasn't regrown a single hair! The vet said it would all come back – it hasn't. We were never really concerned about it anyways, but it does  make his amputation and the surgical site much more noticable!

You can see in this picture – it actually makes it look like he has more hair than he does, too. In normal light and in person, it's much balder than that.