||Pre-B ALL makes up 5% of all non hodgkin lymphoma and 30% of all childhood lymphomas/leukemias. Of acute lymphomblastic leukemias, 85% are B-cell and 15% are T-cell. Many paitents present with hematologic symptoms; (children with pancytopenia 2ndary to marrow involvement). The peak incidence of pre-B ALL is 4 years, most patients are less than 15 years old. Pre-B ALL has a slight male predominance. 90% of patients with Pre-B ALL have a complete remision with 2/3rd cure (ages 2 - 10 yo). A poorer prognosis is seen if: the patient is under the age of 2 (associated MLL gene rearrangements on chromosome 11q13), adolescent or adult, or have one of the following molecular abnormalities: t(9;22) BCR/Abl (3% childhood, 25% adult), t(1;19), or if the neoplastic cells do not express CD10, CD34, CD24, or express CD13 and CD33. Better prognosis is seen if; > 50 chromosomes. This image shows infiltration of the liver with neoplastic B-cells. The cytology of these cells is difficult to appreciate in this image, but usually pre-B ALL cells are uniform in size, have scant cytoplasm and somewhat larger nuclei. Nuclei may show deep subdivision with convoluted lobulated appearance. High mitotic rate can be seen. Diagnosis often includes cell surface marker analysis. BOTH T and B ALL are TdT+ (95%).
B-ALL; +CD19 (100%), +CD10 (80%), +CD79a, +Cytoplasmic IgM heavy chain (20%), - surface Ig. T-ALL; +CD7, + cytoplasmic CD3, +CD2, +CD1, variable CD 4, 8. Certain chormosomal abnormalities are typically seen in pre-B ALL. These include: t(1:19)(q23:p13). 5-6% of pediatric ALL, 25% of a;; pre-B ALL. This translocation involves the E2A gene (transcription factors that bind the E-box in the light chain enhancer region) and the PRL gene (PBX1 homeobox protein). t(1:19) confers a Worse Prognosis. t(4:11)(q21:q23). The MLL gene on 11 is involved in MANY different translocations. 2% of pediatric ALL, 5% of adult ALL. Very high incidence in INFANT ALL. t(12:21)(p12:q22). Involves the TEL gene (HLH protein) and the AML1 gene (DNA binding protein). 27% of pediatric B-ALL. MOST COMMON abnormality in childhood ALL. 3-4% in adult. Other entities in the differential of childhood lymphomas include (with incidence rates): lymphoblastic lymphoma (30%), Burkitt's lymphoma (40%), Anaplastic Large Cell Lymphoma (10%), and large B-cell lymphoma (20%).