Naso-Sinusal T ALL With Aberrant Expression of CD56 Mimicking NK/T Non Hodgkin Lymphoma

T-acute lymphoblastic leukemia (T-ALL) represents 25 % of cases of acute lymphoblastic leukemia (ALL) in adults. The clinical presentation is dominated by a elevated number of white blood cells and in immunophenotype the lymphoblasts are generally Tdt positive and variably express CD1a, CD2, CD3, CD4, CD5, CD7, and CD8. NK/T non Hodgkin lymphoma is presented as a single lesion often ulcerated with torpid evolution affecting the nasal cavity, nasopharynx and/or palate. CD56 expression is while characteristic of NK-cells, and is also expressed on a subset of normal T cells. Its expression in ALL does not exclude the diagnosis and seems to be a prognostic factor of this disease. We report the case of a young woman with nasal cavity tumor which was initially diagnosed as T-cell lymphoma. This diagnosis was finally revised to conclude to T-ALL with CD56 aberrant expression.