In the overwhelming majority of cases, B- or T-cell lymphomas do not express opposite markers, but co-expression of T- and B-cell markers can also be found in some subtypes of lymphomas, such as T lymphoblastic leukaemia/lymphoma (CD79a positivity has been observed in approximately 10% of cases) [2], small lymphocytic lymphoma/chronic lymphocytic leukaemia and mantle cell lymphoma (CD5-positive in tumor cells represent as typical immunohistochemical characteristics) [3]. The gene discussed is CD5; the disease is B-cell chronic lymphocytic leukemia.