Miami, Florida (CNN) -- Elena Espinoza came to Miami's Mercy Hospital with abdominal pain. Peruvian born, she works as a housekeeper. She has no insurance. She's afraid. Afraid of the pain and discomfort in her stomach, and intimidated by the building and the system she has come to for help -- for which she can't pay.
Dr. Joe Greer has tried to help her relax. He's a gastroenterologist on a humanitarian quest to provide health care to those who don't have the money to pay him -- the homeless, the poor and immigrants. It's a trip that has taken Dr. Pedro Jose "Joe" Greer under highways and bridges, to homeless shelters, and even to the White House.
"I don't know when it became socially acceptable in our country to refuse a patient because they have no funds," he told CNN.
"It goes against all the ethics and morals that we know," he said.
It's this commitment that earned Greer a 2009 Presidential Medal of Freedom, for his 25 years of dedication, at a White House ceremony with President Obama.
"On one hand I'm extremely honored, and on the other hand, it's sort of a funny society for being rewarded for what you're supposed to do," he said.
Greer was born prematurely in Miami in 1956, while his mother was visiting from Cuba. He and his mother returned to Cuba, but his entire family fled when Fidel Castro took power in 1959. Half Cuban, and half Irish, Greer likes to call himself, "Cubish." Big, burly and playful, he enters rooms with handshakes, kisses for the ladies, and a bagful of jokes that put people at ease.
On this day, he's using an endoscope, to look down Elena Espinoza's throat, into her esophagus, for a possible malignancy.
Joe Greer sees many patients who can't pay him.
His life was changed forever during his internship, when a homeless, nameless patient Greer had been treating died alone. He searched for the man's family in shelters and under Miami's highways, to no avail. He returned to the area recently with CNN and recalled his amazement.
"I saw a world that I didn't know existed," he said, recalling his search. "I was shocked. This was my own back yard."
It was a time when words like crack and AIDS were first being used and cities were struggling with homeless populations.
"We look at them as other people. 'Those people,' " he said. "We're no different. Believe me, you do a colonoscopy -- all colons look the same," he said.
Greer still sees patients at the St. John Bosco clinic in Miami, a Mercy Hospital facility that cares for disadvantaged adults and children.
He also helped found the Camillus Health Concern in 1984. The clinic has treated more than 5,000 homeless, and low-income patients a year for 25 years.
Last month, the building was named after Greer, on its 25th anniversary. Like a stand-up comic, "Dr. Joe," holds a room with stories, from one unforgettable night from yesteryear.
"There's a stabbing. The guy comes into the clinic. We're going to call 911, and he says, 'No, I trust you guys.' " Laughter from his friends and co-workers begins to fill the room.
"I say, 'OK, let's get you to the back,' and the docs are saying, 'What are we going to do for him?' I said, 'I don't know, but it's a brand new carpet for God's sakes,' " he recalls as the crowd erupts in laughter.
But Greer has a serious side as well. He's part of a new medical school with a new curriculum, at Florida International University, called Medicine and Society. He's teaching a class of 43 that health care is more than medicine. He says it's about humanity and people, which he says, has been lost by his profession. During their schooling at the university, students will be assigned inner-city families to monitor and care for.
The students, he said, are what gives him hope.
"They're young and idealistic, and they want to save the world. And what we need to do is keep putting more oil in the tank. ... Yes, they can make it better," he said.
During one lecture he used that sense of humor to relate to his students.
"You can use your positions to reform and help people, and you'll also have very nice cars -- and the ones that have the fastest cars can help the poor the quickest," he said, as smiles went around the room.
And then he got serious. While a national health care debate rages, he explained to his students how he sees it.
"This is not health reform, what is going on right now ... this is nothing more than coverage reform."
And he connects the real world to the science in their textbooks, as he explains what's really involved with a typical procedure like a colonoscopy.
"It's the day and night before, when you don't eat, but have to go to the bathroom all day," he explained.
"In today's economic times, you do that, they're going to lose a day and a half of work. People are worried about losing their work."
And, he reminds his students that there are people like Elena Espinoza, who need help.
"The esophagus looks pretty normal," said Greer, back in his examination room at Mercy Hospital.
On this day, far away from any health care debate, he and his team were simply trying to make Elena Espinoza feel a little better. He thinks it's gastritis -- an inflammation. Not cancer. He will do further testing, but, for now, the news is good for Espinoza.
As she begins to come out of the anesthesia, Greer gently comes to her bedside.
"Tengo buenas noticias," he says with a reassuring smile. "I have good news"
"Aye, Que bueno," "How wonderful," she responds, as he kisses her gently on the cheek.