Moreover, whereas BRCA1/2 neoplasms tend to be ER-, especially in connection with P53 mutations, and tend to include an excess of the medullary histological type (Lakhani, 1999; Phillips, 2000), the tumours in these concordant MZ twins were not medullary, and tended to be ER+, without a link to P53 mutations (Table 3, Figure 2). The gene discussed is BRCA1; the disease is neoplasm.