US STOCKS-S&P, Dow hold gains even as Yellen paints bleak picture
* Yellen says to approach rate hikes cautiously
* Celgene weighs on Nasdaq
* Indexes: Dow 0.21 pct, S&P 0.29 pct, Nasdaq 0.08 pct (Updates to early afternoon)
By Yashaswini Swamynathan
June 21 (Reuters) - The S&P and the Dow held on to gains on Tuesday even as Federal Reserve Chair Janet Yellen warned of a slower pace of economic recovery and global risks including Britain's possible exit from the European Union.
The Nasdaq was little changed as biotech stocks weighed.
"The pace of improvement in the labor market appears to have slowed more recently, suggesting that our cautious approach ... remains appropriate," Yellen told the Senate Banking Committee.
The Fed left interest rates unchanged and cut the economy's growth forecast last week after surprisingly weak monthly hiring data put the economy's recovery in question.
Weak productivity, slowing economic activity and financial developments abroad led the committee to expect interest rates to remain low for "some time", Yellen said. Continuación...