A brain tumor is still the number one speculation circulating around Katherine Heigl's 'Grey's Anatomy' character, Dr. Izzie Stevens, though there are other interesting posibilities as well.
Several speculations have circulated around Dr. Izzie Stevens, one of "Grey's Anatomy" characters, regarding her recently complex situation with her deceased fiance, Denny Duquette. E! Online's Kristin Dos Santos has given some speculations about what truly happens to Izzie, played by Katherine Heigl.
Similar to what has already been speculated previously, Kristin first guesses that Dr. Izzie's character may suffer from a brain tumor. Though "Grey's Anatomy" creator, Shonda Rimes, has made a statement to EW's Michael Ausiello hinting that Izzie's brain tumor is only a rumor, Kristin thinks that Izzie's recently behavior has a strong implication of someone suffering from a brain tumor.
Next assumption implies that Izzie's character could have lost her mind. In other words, Izzie may become mad for she is having hallucinations over the dead Denny Duquette. Another hypothesis suggests that Izzie may suffer from a post-traumatic stress disorder because she is too busy fighting for surgeries.
Other than those speculations, Kristin also believes that Izzie may have an overactive imagination which proof comes from the fact that Izzie has sex with the dead Denny in her mind. Finally, the last assumption lets out the possibility of Izzie already becoming among the dead people too.