[Alveolar rhabdomyosarcoma with massive infiltration of the bone marrow as its initial manifestation]. / Rabdomiosarcoma alveolar con infiltración masiva de medula ósea como manifestación inicial.

We report a case of alveolar rhabdomyosarcoma (AR) with massive infiltration of bone marrow at presentation, and initial diagnosis in bone marrow aspirate. A 35 year old man presented with a submandibular mass, and hematomas after mild traumatisms. Peripheral blood showed thrombocytopenia and a normocytic anaemia. Bone marrow film showed diffuse involvement by undifferentiated blasts with rhabdomyoblastic features. Subsequent biopsy of submandibular lymph node confirmed the diagnosis with positivity for specific muscle actin and desmin, and negativity for lymphoid markers. Initial presentation of AR with extensive bone marrow involvement is extremely rare, and it could lead to wrong diagnosis and treatment of acute leukaemia, with the serious consequences that this would have. Immunohistochemical study and morphologic differential features can be of great diagnostic help.