Shares of Cigna (CI -7.89%) were dropping Thursday. The stock was down 8.4% as of 1:20 p.m. ET but had lost as much as 11.3% earlier in the day. The leg down comes as the S&P 500 gained 0.2% and the Nasdaq Composite lost 0.2%.The insurer reported earnings before the market open, missing certain estimates and offering guidance that disappointed investors.The numbers didn't look greatWhile Cigna's Q4 revenue of $65.65 billion beat Wall Street's estimate of $63.44, rising medical costs led to a much more signi ...