Https://doi.org/10.1093/bjd/ljad206 Dear Editor, Vismodegib and sonidegib are sonic hedgehog inhibitors (SHHIs) available for the treatment of advanced basal cell carcinoma (BCC).[1] There has been some controversy around the risk of development of cutaneous squamous cell carcinoma (SCC) in patients with advanced BCC treated with SHHIs.[[2], [4]] However, cases of sarcomatoid differentiation during the treatment of BCC with SHHIs have not been previously reported. Histopathological examination described a 15 × 11 × 7 cm tumour constituted of a dermal and hypodermal infiltrative BCC component and a high-grade undifferentiated sarcoma with epithelioid morphology in depth, showing vascular invasion and infiltration of the sternum and the fifth and sixth ribs. [Extracted from the article]