The stock market is full of unproven, speculative stocks that aren't suitable for the average investor. However, if you're aware of company-specific risks and willing and able to accept the consequences, speculative stocks can occasionally turn out to be big winners for a portfolio. With that in mind, the Fool's health care bureau chief, Brenton Flynn, outlines two of 2013's best-performing (and speculative) stocks in the industry and offers a few words of caution to prospective buyers.

Brenton Flynn has no position in any stocks mentioned. The Motley Fool recommends Illumina and Pacific Biosciences of California. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.