US STOCKS-Worst day in 10 months as Wall Street reacts to 'Brexit'
* Bank shares post largest drop in nearly five years
* Utilities are only S&P 500 sector in positive territory
* Trading volume highest since August 2011
* Indexes down: Dow 3.4 pct, S&P 3.6 pct, Nasdaq 4.1 pct (Updates with source for volume comparative, recasts throughout)
By Rodrigo Campos
NEW YORK, June 24 (Reuters) - The S&P 500 turned negative for the year-to-date on Friday as Wall Street suffered its largest selloff in 10 months after Britain's decision to leave the European Union caught traders wrong-footed.
In the busiest trading volume for a single session in nearly five years, financial stocks led the decline on the S&P 500 with a 5.4 percent drop -the largest for the sector since November 2011.
The S&P 500 lost all the year's gains and suffered its largest decline since late August last year.
Equity futures neared an 11-month high to start the overnight session as markets wrongly bet that the "Remain" camp would prevail in Britain's referendum, but sold off sharply as the results showed otherwise - even triggering a market stop put in place to curtail volatility. Continuación...