It is known that many other small round cell tumours can show a mild, focal, and irregular CD99 immunoreactivity as anaplastic large-cell lymphoma, lymphoblastic lymphoma/leukaemia [12, 13], poorly differentiated synovial sarcoma (round cell variant) [14, 15], between 10% and 25% of rhabdomyosarcomas [16], and approximately 20% of desmoplastic small round cell tumour [17]. This evidence concerns the gene CD99 and rhabdomyosarcoma.