A 51-year-old man has noted constant, dull right hip pain for the past 3 months.

On physical examination, he has a diminished range of motion of the right hip.

X-Ray reveals a 10 x 13 cm mass involving the right pelvis. The mass has

irregular borders and there are extensive areas of bony destruction along with

some scattered calcifications. Grossly the mass has a bluish-white cut

surface. Which of the following is the most likely diagnosis?