TIA1 and neoplasm: Furthermore, in the first reported case of extramedullary OS characterized by the spontaneous regression of the primary lesion, T cells that are CD8-positive, T-cell restricted intracellular antigen-1 (TIA-1)-positive, and granzyme B-positive appeared to infiltrate the primary lesion, suggesting that the immune system may have played a role in triggering the spontaneous tumor regression (61).