SMARCB1 and chordoma: Conventional chordomas with focal loss of SMARCB1/INI1 displayed two different staining patterns in neoplastic areas: 13 cases showed a mosaic pattern of protein loss, with isolated single/small foci of negative cells closed to other foci of cells that retained SMARCB1/INI1 (Figure 1A); 8 cases showed protein loss in large areas, looking like ‘subclonal’ foci within the tumor (Figure 1B).