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.