UPDATE 1-Pandora Media lowers outlook, shares tumble

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Dec 4 (Reuters) - Pandora Media Inc lowered its guidance for the fourth quarter, sending its shares down 20 percent in after-hours trading.

The online streaming music service said on Tuesday that it expects fourth quarter revenue of $120 million to $123 million. Analysts were expecting revenue of $130.3 million, according to Thomson Reuters I/B/E/S.

The company reported better-than-expected third quarter revenue, up 60 percent to $120 million, beating analysts' forecast.

It also said that mobile revenue, an important metric, rose 112 percent to $73.9 million for the third quarter.

Still, the company warned that revenue would come below previous expectations.

"This is a conservative guidance issue," said Rich Tullo, an analyst with Albert Fried & Company.

Shares of Pandora Media closed up 5.4 percent at $9.45 but shed 20 percent after the results were released.

(Reporting By Jennifer Saba in New York; Editing by Bernard Orr)