Bump on top of foot

I have a very painful bump on the top of my foot.  X-ray and MRI came back negative for a cyst and my podiatrist just said maybe it's a fatty tissue mass and ordered another MRI.  I have been treated for this since March.  This is taking way too long. The pain has been unbearable and am at my wits end.

Description:

A little larger then a golf ball.
Has increased in size since I first noticed it.
Soft almost spongy, but seems to be getting firmer and more pain.
When I flex my foot it is hard as a rock.
It now seems to be changing color very lightly, almost blue.

I am proficient with google but am having a hard time coming up with any ideas of what this could be.

Any and all help is greatly appreciated!

[Yena H Do, DPM]

not sure what this could be...however, a surgical excision of the mass will give you an answer.  also, it would be a good idea to remove it and send it to pathology to rule out any malignancies.