TBX1 and skin basal cell carcinoma: Co-immunostaining with the cell proliferation marker Ki67 in a subset of samples, showed that in cases with “P” pattern most of the cell proliferation occurs in the peripheral, palisade layer of the BCC lesion and the majority of Ki67+ cells was also TBX1+ (76%, n = 404 from three samples, Figure 2A and Figure 3A).