100 patients were investigated during the year 2022 with the diagnosis falling under different types of diseases. The cases came from the municipality of Bacău, and the investigation was carried out in the Clinical Laboratory of the Bacău County Emergency Hospital. The following classic working methods and techniques were used: blood smear, May-Grunwald-Giemsa panoptic staining and the leukocyte formula using the SYSMEX XN-3000 hematology analyzer. The main plus or minus variations in the number of leukocytes recorded, associated with some conditions benign (more common) or malignant were: leukopenia, agranulocytosis, lymphocytopenia, leukocytosis, eosinophilia, basophilia, lymphocytosis and monocytosis. Both sexes and all age groups can suffer, within some diseases, more or less significant changes in leukocytes, with different pathological meanings.
