Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Navidea Biopharmaceuticals (NYSEMKT:NAVB), a developer of precision diagnostics and radiopharmaceutical agents that help physicians in staging cancer, plunged as much as 18% after announcing the expanded approval of Lymphoseek for use in head and neck cancers. Shares have since rebounded a bit and are now down a tamer 7% as of this writing.

So what: According to its mid-afternoon press release, Navidea announced that the Food and Drug Administration made Lymphoseek the first and only FDA-approved sentinel lymph node biopsy radiopharmaceutical agent for use in head and neck cancer patients with squamous cell carcinoma of the oral cavity. With this approval physicians will now have a new weapon of accurately mapping cancer-positive lymph nodes associated with oral cavity cancer, and it'll further expand Navidea's potential revenue stream. Navidea also has an additional supplemental new drug application for Lymphoseek under review by the FDA which could further expand its usage. The PDUFA decision date on that sNDA is Oct. 16, 2014.

Now what: "So if the news is positive, why did Navidea react so negatively?" That likely had to do with that fact that over the past three weeks its shares had rallied 39% in anticipation of an expected approval of its Lymphoseek sNDA. If you look at the rapid up and down spike on today's intraday chart just minutes after the release of the FDA's approval you'll get a picture-perfect example of what emotional trading looks like. While this news is a clear positive for Navidea, as I noted earlier this week it could be years before the company turns the corner to profitability. Though sales have been increasing, the initial ramp-up has been slower than I would have expected, leading me to believe that shareholders could be waiting a while before they have an opportunity to see sizable gains.