* FTSEurofirst 300 down 0.5 pct, Euro STOXX 50 down 0.4 pct
* BASF falls after cutting earnings guidance
* AMS tumbles sharply after weak results
* Altice up as investors buy into Cablevision (Adds detail, quote)
By Sudip Kar-Gupta and Alistair Smout
LONDON, Oct 27 (Reuters) - European stock markets fell on Tuesday, moving further away from last week's two-month high after a drop in the shares of BASF and Novartis weighed on markets.
Semiconductor stocks also suffered after Austria Microsystems warned late on Monday of weak fourth-quarter results. Austria Microsystems' shares slid 14.2 percent while rival Dialog dropped 2.2 percent.
The pan-European FTSEurofirst 300 index, which had risen to a two-month high on Friday after a Chinese rate cut drove up world stock markets, declined 0.5 percent, while the euro zone's blue-chip Euro STOXX 50 index fell 0.4 percent.
BASF shares dropped by 4.6 percent after the chemicals group lowered its full-year earnings guidance due to weak sales in China, Brazil and other emerging markets.
"While the results were in line with expectations, and the downgraded FY15 outlook was anticipated, the detail is troublesome," analysts at Investec said in a note.
"The comment on 'no volume momentum in September' is likely to be seen as bearish for 4Q15, in our view."
Novartis retreated 1.6 percent after it reported a fall in third-quarter core net income that missed analyst forecasts.
Twenty-two percent of companies in the STOXX Europe 600 index have announced results so far, of which 63 percent have met or beaten analyst earnings forecasts and the rest have missed, according to Thomson Reuters StarMine data.
However, StarMine also shows that only 48 percent of companies have met or beaten revenue forecasts.
The FTSEurofirst is up around 8 percent since the start of 2015, but down 10 percent from its 2015 peak reached in April.
Among risers, telecoms group Altice rose 5.2 percent after BCP and CPPIB said they would buy 30 percent of Cablevision alongside Altice.
UK-listed pharmaceutical Shire shot up to the top of the FTSEurofirst 300 in mid-morning trade after positive results from trials of its dry eye drug kept it on track for a potential U.S. launch next year, if it is approved by regulators.
Talktalk rallied nearly 10 percent, but remains down over 20 percent in October, after police made an arrest over a cyber attack that may have led to the theft of data from among the 4 million customers of the British broadband provider and rocked its shares last week.
Today's European research round-up
Editing by Mark Heinrich