Large mass on the inside of the thigh recently biopsy that came back malignant. what type of cancer is likely?

Check pathology rept: See what the pathology report shows so you can get the best and most appropriate treatment. Best of luck with the therapy.

Any kind: I would guess sarcoma, melanoma, or any other soft tissue or skin malignancy. That said, it could be anything starting in the area or metastatic to the skin/subcutaneous tissue or to a local lymph node from somewhere else. Please wait for the final diagnosis to be made and make sure you see a specialist with expertise in the field. I truly wish you the best. Fight well and God bless.