Myeloid sarcoma (MS) is a rare extra-medullary manifestation of acute myeloid leukaemia (AML) in the form of a first manifestation, progression or recurrence. Mostly located in the bones, it has the particularity of reaching the ENT sphere by mimicking common patho-logies, leading to a delay in diagnosis and treatment. The -mastoid involvement that we have encountered in our clinical -practice (clinical vignette) shows the complexity of identifying this pathology, with very few cases reported in the literature. The anamnesis, including a -history of AML, and the clinical examination help to guide the investigations. Targeted imaging, in this case CT/MRI combined with a biopsy of the lesion and a marrow puncture, is used to make the -diagnosis. Treatment with chemotherapy is indicated and rapidly initiated.