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 Illumina (NASDAQ:ILMN) sank 10% today after Roche Holding said that a deal to buy the DNA sequencing equipment specialist is no longer imminent.

So what: In an interview with Swiss newspaper SonntagsZeitung, Roche Chairman Franz Humer said that Illumina is "definitively" off the table, forcing short-term speculators traders to quickly head for the exits. Humer blamed the broken deal on Illumina's unwillingness to back off its "excessive price demands" -- Roche's hostile bid of $44.50 per share was rejected, as well as a sweetened offer of $51 per share -- but a few Wall Street analysts think that the stock remains a particularly attractive growth pick.

Now what: I'd look into this pullback as a possible buying opportunity. Humer's interview "discounts Roche's intent to purchase Illumina medium-term," wrote ISI Group analyst Ross Muken in a note to investors yesterday. "We do not believe this precludes Roche from returning to Illumina as a targeted asset in the future and does not diminish its attractiveness as a potential M&A target."

So while today's news is disappointing to Illumina bulls holding out for a short-term bump, it might be a chance for long-term investors to buy some solid growth on the cheap.

Fool contributor Brian Pacampara has no position in any stocks mentioned. The Motley Fool recommends Illumina. 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.