RESUMEN
INTRODUCTION: Myeloid sarcomas are uncommon proliferations of immature myeloid cells occurring in any extramedullary organ. We report here two cases of myeloid sarcomas in patients with, respectively, a polycythemia vera and a myelodysplastic syndrome. CASE REPORTS: The first is an 81-year-old woman who presented with osteolytic lesions. Diagnosis has been highlighted using anatomopathological study after bone marrow biopsy, but it was delayed because of a very localized basin lesion and few positive myeloid markers. The second patient is an 86-year-old man who presented with pancytopenia and several lymph nodes. Lymph node cytology failed because of the rarity of blast cells. Diagnosis was done after anatomopathological study on lymph node biopsy which revealed a localized form of myeloid sarcoma. CONCLUSION: The diagnosis of myeloid sarcoma must be considered when unusual tumors occur in patients with a chronic myeloid disease. In that case, therapeutic options are those of an acute myeloid leukemia.