[Morphological diagnosis of myeloid sarcomas].

Myeloid sarcoma (MS) is an extramedullary tumor made up by myeloid blasts that may be undifferentiated or show varying degrees of maturation. This paper gives the results of morphological and immunohistochemical studies of 15 cases of MS. The patients' age was 32.7 +/- 14.3 years. The most involvement was observed in lymph nodes (6 cases) and vertebral bodies with spread to the epidural space and soft tissues (3 cases). Differentiated MS was diagnosed in 60% of cases. The immunohistochemical profile of MS was characterized by the expression of MPO (100%), CD68 (92.8%), CD34 (77%), CD 117 (53.8%), lysozyme (50%), and TdT (44.4%). The blast structure similarity of myeloid blasts and other cells to chromatin makes MS difficult to diagnose. Without immunohistochemical study, MS is misdiagnosed and most frequently misinterpreted as one of the types of non-Hodgkin's lymphoma.