All eyes were on Britney Spears as she celebrated her 27th birthday at NYC hot spot Tenjune on Dec. 2. "She was wearing a tight dress that showed a lot of cleavage,", says a partygoer. The super-sexy Roberto Cavalli dress was the perfect choice to flaunt her figure, says an insider close to the singer. "She made her boobs look great by packing them into that dress!"

Britney's breasts made such an impression, it added fuel to the ongoing speculation that she may have had a boob job.

Did she or didn't she? For more on why Britney is able to show off her breasts, pick up the latest issue of Life & Style, on newsstands now!

Photo Credit: Ramey