In this case, lapatinib, a tyrosine kinase inhibitor (TKI) that targets EGFR1 and HER2, was used as part of precision therapy for metastatic GIST in an 8-year-old, 2.7 kg, spayed, female mixed-breed cat, guided by the high expression of these receptors in the tumor. This evidence concerns the gene ERBB2 and gastrointestinal stromal tumor.