Officials say the attack took place in Canarsie near the East 105th Street L train station.
The suspect took the victim's cell phone. Police say the suspect fled the scene in a black mask.
Authorities say the teen is being treated at Brookdale Hospital.
It is not clear if robbery was the motive for the attack. No arrests have been made.
An hour after this stabbing, a man was shot in the thigh on a Queens subway train.
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