In the past, the only remedy for these conditions was surgical removal, which could cause the risk of blood loss and even death. But now, catheters have been developed and the growth is injected with substances like biological glues and absolute alcohol to break down the lesions.
The condition, which develops in vitro when the vein-artery system becomes intertwined, is not genetic. It should also not be confused with external hemangiomas, which are commonly known as "strawberries" and often disappear without treatment.
"No one knows why the vascular system organizes like this," said Rosen. "It's a complicated affair, and unlike birthmarks, these malformations are part of the body tissues."
As is typical in these cases, the lump on Rohit's hand was small at birth but eventually grew at the same rate the child grew, according to Rosen. By the time he was 4, the mass involved his forearm and was so large none of his fingers were visible.
"His hand was filled with blood, and ... he literally had to live with his hand above his head," said Rosen.
The doctor described the boy as "charming" and was surprised at his adjustment, despite the pain and disability. Local doctors had told the family, "There was nothing to be done."
Since arriving in New York, the boy, who speaks "superb English," has acted as translator for his family, none of whom, except the uncle, speaks English.
For the last year, Rohit's mother was unable to come to the United States because she had no visa. But hospital officials said Rosen, whom they described as a "modest" man who didn't like fanfare, successfully pleaded with the U.S. embassy to secure her visa so she could be with her son for the final round of surgeries.
Rohit was understandably nervous before this week's surgery, they said.
"He's already gone through several of these, but like with all little kids with the anesthesia mask, he's smiling for a few moments, then he freaks out and cries and then settles down," said Rosen. "He's a really sweet kid."
Rohit's prognosis is "excellent," according to Rosen, and the boy is already beginning to be free from pain and has a functional hand. "You can see his hand and fingers."
Sadly, Uncle Kumar, one of the heroes in Rohit's story, was unable to come to New York City for the final treatment because of family issues in Pakistan, but in his stead was his son, Pawan Kumar, 22, who also speaks English and works as a hotel manager in Texas.
With the mother's visa now secured, both of Rohit's parents also were there.
"It was very emotional for them," Pawan Kumar said. "He said he was really missing his mom.
"Dr. Rosen in an angel for us," Kumar said. "He is the best guy, and this is like a dream come true.
"If God gives us this problem, God gives us a solution," Kumar said. "He gave these doctors to us."