ERBB2 and granular cell tumor: Previously described success stories of treatment with tyrosine kinase inhibitors, as it has been shown for human epidermal growth factor receptor 2 (HER2) positive breast cancer (Schlam and Swain 2021) or chronic myeloid leukemia (Kim et al. 2017), are often based on specific mutational patterns, which are rarely found in GCT (Shen et al. 2018).