For such a relatively small invader, the chestnut-sized brain tumor was insidiously positioned to do its work.
As it wrapped itself around Ken Baker's pituitary gland (the pea-sized organ located beneath the brain and behind the nose), starting some time in his mid-teens, the tumor reduced his testosterone level, flooding his body, instead, with the female hormone prolactin, which allows for the production of breast milk.
Typically, a nursing mother's prolactin level is 200 nanograms per milliliter. When Baker's illness was discovered in 1998, his level was 1,578.
"I was gleeful almost when I saw those numbers," said Baker, now 30, who grew up in Hamburg and currently lives in the San Francisco Bay Area where he is a senior writer for Us weekly magazine.
At that point, at least Baker knew he was physically sick, something he hadn't considered even with the bizarre symptoms he experienced.
He now understands his confused adolescence that dragged into young adulthood. He wasn't crazy. He wasn't weak-willed. He wasn't asexual. He wasn't a loser or a freak or a fake.
Finally, at age 28, he had an answer to so many questions: why he couldn't get an erection, why once while he ran a marathon his engorged nipples hurt and leaked milky fluid. Why his shape, which caused his Colgate University hockey teammates to call him "Pear," wouldn't change no matter how much he starved himself and how much iron he pumped.
"I didn't know," said Baker. "Nothing is normal when you are a teenager and your body is changing so much. On the outside, I was so cool. On the inside, I was hurting."
A testosterone storm
After the tumor was discovered, Baker took medication for several months to try to shrink it. When that was unsuccessful, he underwent an operation on July 8, 1998, in Cedars Sinai Medical Center in Los Angeles. The procedure was potentially dangerous because the tumor lodged near the artery that is a main blood supply source to his brain.
But once the tumor was gone, so was the war that Baker had waged with his body. It explained why he was nearly uninterested in sex as an adolescent yet wildly eager to prove that he was a sexual being, both to himself, to potential partners and to his locker room buddies.
Now that he knows, he has split open his life in detail in "Man Made: A Memoir of My Body" due out in March from Tarcher Putnam as its lead spring title. Not only does Baker reveal intimate feelings and observations, he describes his frustrated sexual attempts - at length and in such raw detail that some readers might be offended by it. One remembrance was a trip that he and his girlfriend made to Toronto's Sutton Place hotel so he could lose his virginity on his 17th birthday.
Twelve years later, a surgical procedure delivered the instant puberty he had craved for so long.
Nine days after the operation, as he roller-bladed along Venice Beach, Calif., Baker recounts that he passed a sleek, shapely blond woman and, uncharacteristically, turned around for a second look.
"My male eyes detect the stimuli and my hormonally healthy brain instantly analyzes the data, at which time it sends its conclusions to my groin ..." he writes, somewhat mockingly.
This was completely new territory. He knew what it felt like to be a man, to be comfortable in his own body.
"My doctor describes it as a testosterone storm," said Baker, the fourth of five boys, who spent his childhood fantasizing about how hockey would help him escape Western New York and his family, including his hyper macho father, he said.
A few months after the surgery, his doctor found that a crumb-sized portion of the tumor remained, forcing Baker to take twice-weekly medication to suppress its growth and to regulate his hormonal level.
"It's no bigger than a Tic Tac," he says of the pill on which his masculinity rests.
Over the years, Baker made some cries for help, but he was unsure what he needed. He saw a psychologist while he was at Colgate on a full hockey scholarship. During that time, he was so claustrophobic that he walked up 33 flights of hotel stairs, seven times in one weekend, rather than use an elevator.
"At a certain level it was a tough guy denial," said Baker, whose late father avoided doctors even when he was seriously ill. "I'm a hockey player. I break fingers. I can tough anything out."
Wearing a goalie's mask
The ice rink was Baker's sanctuary. There he could block out thoughts and feelings as adeptly as he blocked the shots that flew at him. At 16, he was the goalie on the winning United States National Hockey Team. By the time he graduated from college, however, he was so demoralized that he quit the game.
"My career was cut short by this biological enemy," he said.
"I let it (his illness) go so long, that's the tragedy," said Baker, a charmingly likable guy who gained a following at the Newport News Daily Press in Virginia, where he co-wrote a column called "The Adventures of Ken&Glenn," which recounted their young adult escapades.
"When I didn't feel masculine enough or strong enough or sexy enough, I'd write a column about going out to pick up women and be this other guy. It's a complicated subconscious kind of thing to do, but it was a survivor's instinct."
Baker spares nothing in the book: his parents, his brothers, his distaste for Buffalo and his hometown of Hamburg. Nor does he spare the powerful story that only he can tell.
"I would feel stupid if I didn't write this book," he said. "If I didn't tell the mistakes I made."
Now that people have read the book (in rough form) they've started asking him why he didn't say anything.
"I didn't tell them because I didn't know," said Baker, whose headaches were so severe at times that he put an ice bag on his head. "For a long time, I was so tucked away behind sandbags of repression."
His mother, Marcia Seiflein, said she attributed the headaches to allergies or the fact that she often had headaches.
"Even after he was diagnosed and I asked if he was having symptoms he told me "No,' " she said. "Then when I read the book, I found he had all these things going on and never could tell us. Being a man, he didn't want to discuss them with his mother."
And Baker could never say anything to his late father, who, ironically, reminded him often not to "knock any girls up" and related to Baker mainly through sports, including smuggling hockey equipment from Fort Erie, Ont., into the United States.
"The drive, instilled in me by my dad, was my big motivator," said Baker, who made peace with his father before he died by telling him that he wasn't perfect "but I didn't want anyone else."
"Dad got to see me be a journalist," said Baker. "I realized I could do something other than hockey and he could be proud."
Revealing his secrets
Writing the book was therapeutic, said Baker, adding that it was his turn to reveal secrets after years of doing so with other people.
"All I've done is tell other people's stories and that's a safe place to be," he said, referring to his internships at The Buffalo News and as a news desk assistant at ABC News, where he was an intern, and his career at People magazine. "But this is an almost a karmic need I have to give back what I've had given. It's very West Coast."
For years - though hockey was once his lifeline - Baker couldn't even watch games on television. After his operation, though, he asked his mother to climb into the garage rafters, get his equipment out and send it to him in California.
It seemed to fit the new Ken just right and it sparked in him a desire to see how he could play with more stamina and the muscles he never had before.
Baker has just signed to play with the Bakersfield Condors of the Double AA West Coast Hockey League for a year and plans to write a book about the experience.
"I need to see this through and end hockey on my own terms," he said.
He's being supported in all his endeavors by his wife, Brooke, whom he met and married after his surgery. Baker dedicates his book to his wife, who plays with the nationally ranked Ultimate Frisbee team Fury.
"Brooke Baker is my ultimate friend and lover," he writes. "I speak to you, the reader, only by standing on her shoulders."
Baker organized a marathon he calls Tread for the Head, which raised $2,000 to support the Ken Baker Pituitary Tumor Fund at Cedars Sinai Medical Center. Donations will help finance surgery for low-income patients at the hospital's Skull Base Institute.
Baker is scheduled to appear on NBC's "Dateline" on at 9 p.m. Monday - shown locally on Channel 2.