The effectiveness of mTOR inhibitors as medical therapy for TSC‐related tumours, including renal AMLs, subependymal giant cell astrocytomas (SEGAs) and angiofibromas, has meant that there is a reducing clinical burden from such lesions and less need for surgical resection of tumour tissue (Curatolo and Moavero 2012; Bissler et al. 2013; Franz et al. 2013; Koenig et al. 2018) As a result, most participants (14/19, 74%) did not have any tumour/affected tissue available for testing, which may have reduced our diagnostic yield. The gene discussed is MTOR; the disease is subependymal giant cell astrocytoma.