Harrison, 28, was part of a trade this week in which he would join the Philadelphia Eagles in exchange for running back Ronnie Brown. But, ESPN reported, a physical examination of Harrison revealed a brain tumor and the trade was nullified.
Harrison, in his sixth season in the NFL, has rushed for 1,681 yards in his career. He started with Cleveland, played for Philadelphia, returned to Cleveland and then joined Detroit before this season.
He had 41 yards in 14 rushing attempts in 2011.
Detroit, which is without running back Jahvid Best due to concussion symptoms, is thin at the position. The Lions said they signed running back Eldra Buckley, who was released by the Eagles Sept. 3, to the active roster.