Clinically if this swelling is since long and slowly growing then chances of cancer is less , if its rapidly growing and recently visible than chances of soft tissue
sarcoma(liposarcoma/fibrosarcoma/malignant fibrous histiocytoma
2nd this is you get done MRI and in any doubt regarding cancer/sarcoma go for Incision biopsy
that give final confirmation of malignancy. dont worry meet Expert Surgeon doctor and if he says that you have to remove tumor
then definately its right choice.