For example, 3% of desmoplastic small round cell tumours have FGFR4 V550L mutations [47], and 3.5% of endocrine-treated metastatic invasive lobular breast carcinomas harbour FGFR4 mutations, including N535K/D and V550L/M [48]. The gene discussed is FGFR4; the disease is invasive lobular breast carcinoma.