you mentioned several conditions. what other ones then the ones you mentioned would be. Because all i see is cancer.
There are several conditions where a mass like structure can receive increased blood flow. The more common of which is still a malignancy or cancer, since cancer cells would require extra-nutrition from extra blood flow.
Other conditions would include primary vascular tumors such as hemangiomas or AV malformations, but these are rather not that common.
A biopsy will indeed be helpful, but take into account and discuss with your surgeon regarding the possibility of bleeding if this mass were a hemangioma or AV malformation.
Regards.