Rep. Alan NunneleePatrick (Alan) Alan NunneleeTrent Kelly sworn in as House member Democrat advances to runoff in Mississippi special election House holds moment of silence for Rep. Nunnelee MORE (R-Miss.) is resting comfortably after undergoing brain surgery on Monday, his office said in a brief statement. 

"His family is with him at the hospital and indicated that the surgery went well," according to the statement released Monday.  

The Mississippi congressman had the procedure to remove a small mass found on the right side of his brain. The tumor was isolated, according to a statement released last week

During a House Appropriations Committee hearing Tuesday, Chairman Hal RogersHarold (Hal) Dallas RogersTrump says he'll decide on foreign aid cuts within a week Pelosi warns Mnuchin to stop 'illegal' .3B cut to foreign aid Appropriators warn White House against clawing back foreign aid MORE (R-Ky.) said Nunnelee was in surgery for 12 hours, according to The Associated Press

The surgery took place at MD Anderson Cancer Center in Houston. He has not said how long his recovery is expected to take.