Fig. 4.

(A) Screening for the p53 mutation, based on the formation of Holliday junctions (HJs) when a nucleotide mismatch is present, was undertaken for exons 5–8. p53 mutations were not detected in any of the exons in the low-grade areas of tumor (7B); however, p53 mutation in exon 7 was observed in the malignant component (7M), denoted by the presence of HJs (arrow). The p53 mutation was consistent with the detection of p53 protein in the malignant component (Fig. 3B) (L, ladder; 7+, positive control for exon 7). (B) HUMARA analysis to determine clonality between the benign (B) and malignant (M) components. The near loss of the band for allele A in the digested (D) versus undigested (U) lanes for both the benign (B) and the malignant (M) components indicates they are likely clonal. The faint band in the digested lanes likely represents contamination of bystander nonclonal stromal cells.