Aberrant expression of CD5 in a case of B acute lymphoblastic leukemia positive Philadelphia chromosome

B acute lymphoblastic leukaemia (B-ALL) is a proliferation of hematopoietic precursor cells characterized by the expression of various B-cell antigens. Expression of T cell antigens has rarely been reported in B-ALL. We report the second case CD5+ (Cluster of differentiation 5) B-ALL associated with Philadelphia chromosome (Phi+).

A 38-year old male presented with anorexia and generalized weakness for the last ten days. Hemogram revealed bicytopenia and hyperleukocytosis made of 93% difficult to classify cells. A diagnosis of diffuse large B-cell lymphoma was suspected. An immunophenotyping on peripheral blood was performed. The panel for B- cell lineage chronic lymphoproliferative disorders (B-CLPD) was used. The dim expression of CD45 and the lack of surface immunoglobuline helped to exclude a CD5 expressing mature B cell neoplasm. Then, the diagnosis of ALL was confirmed by ALL panels. Karyotype showed a Phi+. Thus, a diagnosis of B-ALL with aberrant expression of CD5 and Phi+ was established. The patient received chemotherapy according to the modified group for research on adult acute lymphoblastic leukemia philadelphia positive 2005 protocol (GRAAPH 2005). A complete remission at the end of induction was obtained. The patient received consolidation and then, hematopoietic stem cell transplantation. The patient is in complete hematological remission till the date of submission of this report.

Aberrant expression of CD5 associated with Phi+ has rarely been reported in B cell lineage ALL and having a poor prognosis. Pathologists and clinicians should be aware of this entity to avoid confusion with other tumors.