Precursor B lymphoblastic leukaemia/ lymphoma is a neoplasm of lymphoblasts committed to B cell lineage, and may present as leukaemia and/ or lymphoma.Clinically a case is defined as lymphoma if there is a mass lesion and less than 25% blast cells in the bone marrow, and as leukaemia if there are more than 25% blast cells in the marrow with or without a mass lesion.Most cases involve blood and bone marrow (B acute lymphoblastic leukaemia: B-ALL) and a few present with primary nodal/ extranodal tissue deposits (B lymphoblastic lymphoma: B-LBL).There is significant biological and clinical overlap between neoplasms diagnosed as B-ALL and B-LBL.Although some patients present with predominantly lymphomatous involvement, most have or later develop marrow involvement.Similarly patients who present with leukaemia may have or develop extramedullary tumours.Since B-LBL and B-ALL share considerable clinico-pathological and biological properties, they are considered the same disease.The present report discusses the case of a ten year old boy who presented with pathological fractures at multiple sites.His absolute neutrophil count and platelet count were normal, and no blast cells were seen in the peripheral blood at the time of presentation.Biopsy from the fracture site, followed by further investigations proved him to have precursor B lymphoblastic leukaemia.
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