Female

The doctor starts to unstrap you quietly, he seems embarrassed and while you noticed that he was a handsome man before now he seems quite a bit more so. slowly you get up and take a few steps, you realize you are quite a bit lighter and a little off balance. the doctor coughs and finally speaks as you wander toward the mirror "So, you were quite a bit damaged, and the nannos use your nervous system for processing power, so when they got into a human they had more to work with. They fixed the cancer, but they kept going, they um... fixed an underlying genetic condition."

you get to the mirror and see that you are in fact a woman. you stand in stunned silence touching yourself lightly to confirm as the doctor continues "It made you a female, also it started printing us reports... It um... didn't do that before. But it says it has optimised practically all of your functions, you only need to eat 1/10 as much, same with waste. You won't menstruate, but that part of the report was strange. Oh, you will regenerate and you pretty much can't die."

That last part strikes you back into full awareness "You mean I'm invincible?" the doctor pokes you with a tongue depressor, despite being just a small poke it hurts a lot. "Guess not, the nanos did keep the nerve mass of someone twice your size. But pretty much no matter what happens you won't die... so try not to get trapped."