Could A Painful And Tight/swollen Area On Back Of Upper

Could a painful and tight/swollen area on back of upper left thigh be cancer? maybe liposarcoma? It started suddenly with no known injury and has gotten worse (about 5 mos. Now) (larger area... Now reaches all the way into lower left buttocks as well, and more painful, not less)... I am 49 and have had lots of odd symptoms last year and a half.. Odd migrating swelling (but not THIS area.. It has been constant soreness even at rest....) and many small lumps in flank, tricep, abdomen, hip (rt. Side, not left), etc... Many tests, no answers...