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 jewelry retailer Tiffany (NYSE: TIF) sank 10% Tuesday after its current-quarter guidance missed Wall Street expectations.

So what: Tiffany's third-quarter earnings managed to wallop estimates, but a miss on its fourth-quarter outlook -- it now sees EPS of $1.48-$1.58, versus the consensus of $1.63 -- suggests that its recent breakneck sales growth is slowing. When you couple those top-line concerns with dipping gross margins, Tiffany's profitability seems to be under some significant pressure.

Now what: I wouldn't be so quick to pounce on this plunge. "We are, of course, mindful of continued short-term economic challenges and uncertainties in some markets," CEO Michael Kowalski said. But with a P/E of 21, even after today's pullback, Tiffany shares still don't have enough of those risks baked into the price.

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