Figure 3 . SSCP analysis of the p53 gene. Mutation was seen in exon 4 of the DNA from the breast cancer, indicated by an arrow. Figure 4 . Immunohistochemistry with DO7, P53 antibody.
Pathology demonstrates scirrhous carcinoma.
Assessment of microsatellite alterations revealed a breast tumor with the RER phenotype. Genetic instability is believed to result in a rapid accumulation of somatic mutations, once tumorigenesis is initiated. It is speculated that tumor progression was accelerated in this patient and breast cancer developed at the unusual age of 19, and this genetic disorder had probably been inherited from her mother's side of the family. Therefore, it was not surprising that no p53 mutation was detected in DNA from leukocytes of this patient. However, the discrepancy in the results of p53 somatic mutations between the DNA level and the protein level may be open to question.