The S&P 500 fell 0.04% to 1,862.62 in afternoon trading Monday.
The Dow Jones Industrial Average rose 0.29% to 16,409.18, while the Nasdaq fell 0.77% to 4,044.05.
The yield on a 10-year Treasury bond was up 1.09% to 2.70%.
The price of gold was down 0.34% to $1,296.40 per ounce.
Anaheim drug maker Questcor Pharmaceuticals Inc. was off about 4% to $78.26 for a market value of $4.6 billion. The company is expected to report its first-quarter results after market close today.
Aliso Viejo chipmaker Microsemi Corp. slipped about 4% to $23.16 for a market value of $2.19 billion.
The company reported results for the March quarter on Thursday, including an adjusted profit down from the year-ago period and revenue guidance for the current quarter that missed analyst expectations.
Foothill Ranch-based teen and contemporary retailer Wet Seal Inc. fell about 8% to $1.15 for a market value of $97.36 million. The retailer said Friday that it plans to convert its 54-store Arden B chain to Wet Seal and Wet Seal Plus stores in a move to eventually wind down the Arden business.