U.S. stocks mostly extended gains for a fifth day on Tuesday after strong consumer confidence data, but investors' lack of participation suggested the advance was tenuous.

The Dow Jones industrial average <.DJI> dropped 2.27 points, or 0.02 percent, to end unofficially at 12,291.73. But the Standard & Poor's 500 Index <.SPX> inched up just 0.11 of a point, or 0.01 percent, to 1,265.44. The Nasdaq Composite Index <.IXIC> added 6.56 points, or 0.25 percent, to 2,625.20.

(Reporting By Chuck Mikolajczak; Editing by Jan Paschal)