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 medical device company Delcath Systems (Nasdaq: DCTH) were soaring today, gaining as much as 34% in intraday trading on heavy volume.

So what: Just yesterday, my fellow Fool Brian Orelli expressed his disappointment at the fact that management didn't seem terribly on top of the situation with its Food and Drug Administration application. Not to mention the fact that the company seemed like it was being a bit cagey with investors about it. However, Brian also said, "An approval in Europe would certainly help regain credibility in my eyes." And bam! Just like that, credibility restored, as today we got that approval in Europe.

Now what: The CE Mark approval for Delcath's Hepatic CHEMOSAT Delivery System will allow it to start marketing and selling the product in the European Economic Area. That's a very big deal for a development company like Delcath that has yet to generate any revenue. Certainly the company still needs to get its ducks in a row with the FDA, but the European approval provides ample reason for some investor celebration.

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Fool contributor Matt Koppenheffer does not have a financial interest in any of the companies mentioned. You can check out what Matt is keeping an eye on by visiting his CAPS portfolio, or you can follow Matt on Twitter @KoppTheFool or on his RSS feed. The Fool’s disclosure policy prefers dividends over a sharp stick in the eye.