A private equity investment firm is buying apparel retailer Hot Topic Inc. for $600 million, Hot Topic announced today.

Sycamore Partners is paying $14 per share for Hot Topic, a 30.2% premium over the March 6 closing price of $10.75. The deal is expected to close no later than the third quarter, Hot Topic says.

Hot Topic, which sells online and through 808 mall-based stores, was not actively looking for a buyer, a Hot Topic spokeswoman says. “But once the offer was received, the board determined that it was at a premium worthy of consideration,” she says. Other proposals were evaluated, but Sycamore’s offer was deemed the best, she says.

Untethered from quarterly earnings reports and Wall Street expectations, Hot Topic may find room to test new retail ideas. “As a private company will be in a better position to navigate unpredictable market and economic cycles with a long-term perspective, rather than being subject to short-term and quarterly Wall Street expectations,” she adds.

Hot Topic’s e-commerce plans may benefit from that shift. It launched the Blackheart product line in the fourth quarter to sell an expanded collection of dark, edgy, sexy lingerie, accessories and beauty products in some stores and on a dedicated e-commerce site. Hot Topic says it still considers Blackheart a test retail concept. Hot Topic also operates Torrid.com, an apparel site for plus-size women.

Hot Topic, No. 218 in the Internet Retailer Top 500 guide, had $73.1 million in e-commerce sales in 2011. Hot Topic would not provide its 2012 e-commerce revenue.