TP53 and embryonal rhabdomyosarcoma: This observed paucity of TILs was further evaluated in comparison to an immunologically competent model of embryonal rhabdomyosarcoma (ERMS), M3-9-M, a cell line derived from an ERMS tumour that arose in a male C57Bl/6 HGFT+/-;Trp53+/- mouse [49].