The diagnosis of Acute Lymphoblastic Leukemia (ALL) involves a multifaceted approach, integrating clinical findings with comprehensive laboratory investigations. Initial suspicion typically arises from a complete blood count (CBC) revealing abnormalities in leukocyte, hemoglobin, and platelet levels. If these results suggest acute leukemia, a peripheral blood smear is examined for the presence of blast cells. Should acute leukemia remain suspected, regardless of blast cell visibility in the peripheral smear, a bone marrow aspiration and biopsy are necessary. This procedure allows for detailed pathological examination, genetic/molecular testing to identify ALL-associated abnormalities, and flow cytometry to characterize surface antigens on leukemic cells, confirming their lymphoblast origin. A definitive diagnosis of ALL is established when the blast cell count in the bone marrow exceeds 20% and flow cytometric analysis confirms these cells as lymphoblasts. Genetic tests are crucial not only for determining the specific genetic subtype of ALL but also for identifying prognostic markers that guide treatment strategies. It is observed that in over half of patients, blast cell infiltration in the bone marrow exceeds 90% at the time of diagnosis.