Final answer:
The most likely diagnosis for a free floating, painless, cystic mass found posterior and superior to the testis is an ovarian cyst.
Step-by-step explanation:
The most likely diagnosis for a free floating, painless, cystic mass found posterior and superior to the testis is an ovarian cyst. An ovarian cyst is a sac filled with fluid or other material that can cause pain. Although ovarian cysts are usually harmless and often disappear on their own, large or painful cysts may require surgery for removal.