The work could date back to the late 15th Century
A new Leonardo da Vinci portrait may have been discovered after a fingerprint found on it seemed similar to another discovered on his work.
A Paris laboratory found the fingerprint is "highly comparable" to one on a da Vinci work in the Vatican.
Antiques Trade Gazette reported that the work, previously catalogued as "German, early 19th Century", could be worth tens of millions of dollars.
The work previously changed hands for around $19,000 (£12,039).
A forensic art expert found the fingerprint near the top left of the work, corresponding to the tip of the index or middle-finger.
It was "highly comparable" to a print on da Vinci's St Jerome in the Vatican, which was painted early in the artist's career when he was thought not to use assistants.
Infrared analysis showed "significant" stylistic parallels with da Vinci's Portrait of a Woman in Profile, which hangs in Windsor Castle, the magazine reported.
It also said the analysis revealed that the drawing and hatching were made by a left-handed artist, as da Vinci is known to have been.
Drawn in ink and chalks, the young woman's costume and hairstyle reflect Milanese fashion of the late 15th Century, while carbon analysis of the artwork is consistent with such a dating.
Da Vinci scholar Martin Kemp, Emeritus Professor of the History of Art at Oxford University, believes the teenager, shown in profile, could be Bianca Sforza, daughter of Ludovico Sforza, Duke of Milan (1452-1508) and his mistress Bernardina de Corradis.
He suggested this "by a process of elimination".
The portrait, which measures 13ins by 9ins, was sold at Christie's in New York in 1998, in an Old Master Drawings sale as a Young Girl in Profile in Renaissance Dress.
It was catalogued as "German, early 19th century", with an estimate of $12,000 to 16,000, and went under the hammer for $19,000 (£12,039). It was later sold for a similar sum to a Canadian-born connoisseur, Peter Silverman, in 2007.
Mr Silverman believed that there was more to the portrait and began to look into the matter following a discussion last year with Dr Nicholas Turner, formerly Keeper of Prints and Drawings at the British Museum.
The artwork is due to go on display in an exhibition in Sweden next year.