Leukemia, cancer of the blood-forming tissues, is the most common form of childhood cancer. However, even for a child with the most favorable prognosis, leukemia presents innumerable physical, clinic, physicians’ office, and community can do much to prevent some problems and lessen others.

Classification
Leukemia is a broad term given to a group of malignant diseases of the bone marrow and lymphatic system. Current research has revealed that it is a complex disease of varying heterogeneity. Consequently classification has become increasingly more sophisticated and essential, since identification of the subtype of leukemia has therapeutic and prognostic implications. The following is an overview of the morphologic, cyto-chemical and immunologic characteristics of the leukemia.

Morphology and cytochemical markers
Leukemia is classified according to its predominant cell type and level of maturity. As described by the following:

Lympho- for leukemia involving the lymphoid or lymphatic system.
Myelo- for those of myeloid (bone marrow) origin
Blastic and acute- for those involving immature cells
Cystic and chronic- for those involving mature cells

In children, two forms are generally recognized: acute lymphoid leukemia (ALL) and acute nonlymphoid (myelogenous) leukemia (ANLL or AML). Synonyms for ALL include lymphatic, lumphocytic, lymphoblastic, and lympho-blastoid leukemia. Usually the term “stem cell” or “blast cell leukemia” also refers to the lymphoid type of leukemia. Synonyms for the ANLL type include granulocytic, myelo-cytic, monocytic myelogenous, monoblastic, and mono-myeloblastic. There are also much rarer forms of leukemia that are named for the specific cell involved, such as basophilic or eosinphilic leukemia.

Because of the confusion and inconsistency in classifyin the leukemias, acute lymphoblastic and acute nonlymphoblastic leukemias are further subdivided according to another system known as the French-American-British (FAB) system. In the FAB system, the subtypes are determined after a thorough study of the morphology (structure) and cytochemical reactivity of the leukemic cells. Accordingly, ALL is subdivided into 3 types, Li stands for Lymphoblastic leukemia, child type, which accounts for 80{0f0fc6bf5bd959fc253a0668ee6b669dcca87a64289522d38fccac0cb86058d7} to 85{0f0fc6bf5bd959fc253a0668ee6b669dcca87a64289522d38fccac0cb86058d7} of all childhood leukemia and has the best prognosis, ANLL is classified into 7 types and comprises 10{0f0fc6bf5bd959fc253a0668ee6b669dcca87a64289522d38fccac0cb86058d7} to 20{0f0fc6bf5bd959fc253a0668ee6b669dcca87a64289522d38fccac0cb86058d7} of the leukemias in children. The types with the best prognosis are Mi, acute myelocytic leukemia without differentiation, and Mz, acute myelotic leukemia with differentiation.

The various cells also demonstrate different reactions when they are exposed to certain chemicals. For example, lymphoblasts show no reactivity to Sudan black stain and perioxidase, whereas myeloblasts demonstrate reactivity to both.

Another important differentiation between the cell types is the absence or presence of Auer rods, granules containing RNA that appear in the cytoplasm of affected myeloblasts and promyelocytes. Their presence is a strong diagnostic indicator for certain types of ANLL and is associated with improved prognosis.

The main clinical symptoms
• Fever, which the child shows during long time and there is no evident signs of infection
• Pain in joints and bones (ossalgia)
• Pale color of the skin
• Enlargement of peripheral lymphatic nodes of different groups which are usually not painful; during palpation
• Enlargement of liver and spleen
• Fatigue
• Hemorrhage syndrome petechiae, bruises and bleeding)

Laboratory diagnostic
Laboratory diagnostic includes common blood analysis. WBC differential count and sternal puncture. The main dates are:
• Leukocytosis (with leucocytic levels up to 40-100x1o^6) or leucopenia
• Anaemia of hypoplastic origin
• Thrombocytopenia
• WBC count (blasts can be seen in peripheral blood)
• In marrow aspirate blasts are higher than 20{0f0fc6bf5bd959fc253a0668ee6b669dcca87a64289522d38fccac0cb86058d7}