Cancer in Dogs question (Rosco again)

[Gidney N Cloyd]

I posted several days ago about my yellow lab Rosco having surgery to remove a spinal growth that might be making his back legs suddenly lame. I appreciate everyone's good wishes and prayers at that time.
The pathology reports are trickling in and I just now got word his elbow, the original problem before the legs went out, is positive for histiocytic sarcoma; and while the spinal growth is still finishing testing, it's consistent so far with that (histiocytic sarcoma).

So...

Can anyone shed any light on that type of cancer?

Also, does anyone know anything about nutritional treatments like Glycomannan (sp.?)