5. AthenaHealth ( ATHN)

Company profile: AthenaHealth, with a market value of $2.6 billion, provides Internet-based business services to physician practices.

Investor takeaway: Its shares are up 47% this year and have a three-year average annual return of 39%. Analysts give them three "buy" ratings, two "buy/holds," 13 "holds," one "weak hold," and two "sells," according to a survey of analysts by S&P.

4. Skyworks Solutions ( SWKS)

Company profile: Skyworks Solutions, with a market value of $5 billion, makess semiconductor components for wireless handsets, including power amplifiers, integrated front-end modules, and direct conversion radios.

Investor takeaway: Its shares are up 51% this year and have a three-year average annual return of 55%. Analysts give them 11 "buy" ratings, five "buy/holds," and three "holds," according to a survey of analysts by S&P. It's expected to earn $1.87 per share this year and grow by 11% next year.

3. Tempur-Pedic International ( TPX)

Company profile: Tempur-Pedic International, with a market value of $5 billion, makes viscoelastic foam mattresses, pillows, and other sleep system products, which, packaged together, can run several thousand dollars.

Investor takeaway: Its shares are up 52% this year and have a three-year average annual return of 161%. Analysts give them nine "buy" ratings, two "buy/holds," and four "holds," according to a survey of analysts by S&P. It's expected to earn $3.99 per share this year, and grow by 17% to $4.67 in 2013.

2. Fossil ( FOSL)

Company profile: Fossil, with a market value of $8 billion, makes wristwatches under the Fossil, Relic and Zodiac brand names, along with a complementary line of leather goods, sunglasses and jewelry. Its products are sold in department and specialty retail stores.

Investor takeaway: Its shares are up 55% this year and have a three-year average annual return of 119%. Analysts give them five "buy" ratings, five "buy/holds," and five "holds," per S&P. S&P, which has it "buy"-rated with a $125 price target, an 11% premium.

1. Regeneron ( REGN)

Company profile: Regeneron, with a market value of $10 billion, discovers, develops, and commercializes products that fight inflammation, cancer, and eye disease. Last year, it won FDA approval and launched EYLEA for the treatment of wet age-related macular degeneration.

Investor takeaway: Its shares are up 89% this year and have a three-year average annual return of 102%. Analysts give them eight "buy" ratings, one "buy/hold," and seven "holds," according to a survey of analysts by S&P. S&P has it rated "hold," due to its recent share-price jump, but said it has a "robust" pipeline of potential new products.

>>To see these stocks in action, visit the 10 Mid-Cap Stocks That Have Almost Doubled in 2012 portfolio on Stockpickr.
Disclosure: TheStreet's editorial policy prohibits staff editors and reporters from holding positions in any individual stocks.

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