The demonstration of histiocytic markers (CD68 and CD163) and the absence of Langerhans cell markers (langerin and CD1a), T‐cell marker (CD3), B‐cell markers (CD20), mature B‐cell and follicular dendritic cell marker (CD21), B‐cell chronic lymphocytic leukaemia and lymphoproliferative disease marker (CD23) supported the diagnosis of histiocytic sarcoma. This evidence concerns the gene CD1A and histiocytic sarcoma.