<P> Mark's personal life after his marriage is tumultuous . He takes after Doug, having several flings and an affair with Nurse Chuny Marquez, and setting up three dates in one day . He has a brief relationship with a needy desk clerk, Cynthia Hooper (played by Mariska Hargitay in season 4). Hooper leaves him after she finds out Mark doesn't really love her . Mark eventually meets a British surgeon, Elizabeth Corday . Corday is in Chicago on an exchange program, under the guidance of Dr. Romano . Romano's advances on Corday fail, as does her relationship with Peter Benton . Eventually, Mark and Elizabeth begin dating in Season 5, finally forming a stable and happy relationship . During Season 6, Mark discovers that his father is suffering from advanced lung cancer . After David loses his wife and develops end stage lung cancer, he realises that he can no longer live alone, and he moves to Chicago and stays with Mark; after an awkward first meeting, he warms up to Elizabeth very quickly . After an emotional bonding that heals their difficult relationship from Mark's youth, David dies . </P> <P> Mark and Elizabeth begin a more serious relationship and move in together . Mark later buys a house, and he and Elizabeth get married and have a daughter, Ella . Their happiness is threatened, though, when the abusive father of a patient goes on a killing rampage after losing his son to social workers . In a bid to get his son back, he kills and injures a number of people and attempts to go after Elizabeth and Ella . After being shot by an armed bystander, he is brought to the ER . During his treatment, Mark takes him aboard an elevator to go to an operating room . The patient goes into arrest when alone in the elevator with Mark, who withholds defibrillation and allows him to go into vfib and die . He later falsifies records to show that he did attempt to save the patient . Elizabeth suspects what Mark did but lets the matter drop . Later, Rachel appears in Chicago unannounced, citing arguments with her mother, and moves in with Mark and a very reluctant Elizabeth . She sneaks out of the house at night and uses drugs, which clouds her relationship with Elizabeth . </P> <P> While suturing a patient's wound, Mark loses control of his faculties and is temporarily unable to speak . After a CT scan and a biopsy, he is diagnosed with an aggressive form of brain cancer, glioblastoma multiforme, that is thought to be inoperable . Embarrassed, Greene briefly tries to hide his condition, but his cover is blown when he has a seizure while arguing with Carter . With little time, Mark seeks a second opinion from an eminent New York City neurosurgeon, Dr. Burke . Mark is told that the tumor is near a critical section of his brain but hasn't "invaded" it yet and they can perform an operation on New Year's Eve 2000 . Mark's surgery is performed by Burke and things appear to be positive, although it takes him a while to return to his old self . A year or so later, however, Mark finds out his tumor has returned, and Dr. Burke both confirms this and says he cannot operate again because the tumor regrowth is now in part of his brain where an operation would render Mark completely vegetative . While chemo treatment will only allow Mark to live for another 5--6 months, Burke points out: "You should have been dead a year ago, Mark . You got married, saw your daughter be born - I'd say that was time well spent ." </P> <P> At this point, Rachel has run away from Jenn in St. Louis and is staying with Mark and Elizabeth . Though she vehemently denies it, her recreational drug use becomes apparent when her baby sister Ella gets hold of some ecstasy in her backpack and nearly dies after ingesting it in the episode "Damage is Done". When Rachel shows up, Mark can barely control his anger at her, berating her for repeatedly lying to him and for putting Ella in danger . However, he sees her remorse and fear for Ella are genuine; knowing Elizabeth is angry enough for both of them, he hugs Rachel when she starts to cry . When Mark refuses to throw Rachel out of the house, Elizabeth says she won't return home with Ella as long as Rachel is there and leaves home with Ella and moves into a hotel . Unwilling to tell Elizabeth about his condition, Mark stays with Susan during the course of his chemotherapy and radiation treatments . Elizabeth later finds out the truth and wants to come home, but Mark tells her she shouldn't pretend to be his wife just because he's sick; however, she returns anyway and begins helping Mark as his terminal illness advances . </P>

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