Short-sellers have been piling into a number of healthcare stocks lately. This trend lends itself well to the possibility of exploiting a so-called "short squeeze", where share prices rise as short-sellers scramble to cover their positions. We asked three of our top healthcare specialists which stocks they thought short-sellers could be wrong about. Here's what they had to say.

Todd Campbell: Investors are right to be skeptical of medical marijuana stocks. After all, many of these companies are unproven with little to no revenue. That's not the case, however, at Insys Therapeutics(NASDAQ:INSY). Insys has a track record of success thanks to Subsys, a reformulated version of the opiate fentanyl.

Subsys sales jumped 105% to $58.3 million in the third quarter, giving the drug an annualized run rate north of $230 million. That cash flow, plus the fact that Insys is debt free, means the company has plenty of dry powder to market its medical marijuana drug oral dronabinol, assuming the FDA gives the drug a green light.

Insys should file for FDA approval of oral dronabinol soon. If that drug is even half as successful as Subsys it should put Insys in a very good position to advance its medical marijuana clinical programs for epilepsy and brain cancer. Despite these points, sellers are sitting on 12.2 days to cover worth of stock short, which may mean that any good news out of Insys could result in a short covering rally.

George Budwell: Geron Corporation(NASDAQ:GERN) has long been a favorite name among short-sellers, and for good reason. Over its 24-year history, Geron has repeatedly blown up weary shareholders via clinical failures, poorly timed public offerings, and an "all-or-nothing" type approach to drug development in general. The net result has been a promising company that has run roughshod over its shareholder base in its quest to develop a game-changing new drug.

In 2012, CEO John Scarlett set out to reverse this agonizing trend by outsourcing clinical development to save money, and refocusing the company's dwindling resources on the telomerase inhibitor imetelstat as a treatment for a host of blood disorders. Although this reorganization hasn't gotten Geron off the short-sellers' radar, it is finally paying dividends in the form of a major licensing agreement with Johnson & Johnson(NYSE:JNJ).

Last Friday, Geron's shares skyrocketed higher after announcing a deal with J&J for imetelstat worth up to $935 million in milestone payments alone. Given that J&J has a knack for identifying major new drugs early on, I think short-sellers should think twice about continuing to bet against Geron at this point. 

Keith Speights: Rockwell Medical(NASDAQ:RMTI) is another stock attracting plenty of short seller attention lately. As of Oct. 31, the short percentage of Rockwell's float stood at 23.9%. I suspect that number has declined in recent days, though, after an FDA advisory committee gave Rockwell's Triferic a big thumbs up.

On Nov. 6, the Oncologic Drugs Advisory Committee voted 8-3 in favor of the iron-replacement drug. This decision no doubt surprised many of the short-sellers banking on a negative recommendation by the committee.

While Rockwell's shares soared after the committee's announcement, we haven't yet seen a full-blown short-squeeze scenario. Perhaps many skeptics of Triferic expect the FDA to ignore the advisory panel's recommendation and reject the drug. That could happen – but keep in mind that a McKinsey study of FDA decisions from 2001 through 2010 found that the FDA went along with advisory committee's positive recommendations 88% of the time.

If Triferic gains approval, the drug stands to be a big winner for Rockwell Medical. And it could cause some short-sellers to be big losers.