Jasmine Thomas scored 14 of her 19 points in the second half and Michigan State used its stout defense to upset No. 8 Penn State 54-46 in the Big Ten tournament semifinals.
Becca Mills added 16 points for the Spartans (24-7), who held Penn State to 22 percent shooting and enjoyed a 52-38 rebounding edge.
Penn State (25-5) won the Big Ten regular-season title and lost in the tournament semifinals for the second straight season. The Lady Lions fell 68-66 against eventual champion Purdue last year.
Penn State star Maggie Lucas, the conference player of the year, had 23 points and nine rebounds, but she was the only player on her team to score in double figures.
Michigan State will meet third-seeded Purdue in the title game on Sunday.