CD5 negative lymphocytosis mimicking typical B-chronic lymphocytic leukaemia. Description of 26 cases.

We report 26 elderly patients (median age 68.3 years) who met diagnostic criteria for B-cell chronic lymphocytic leukaemia (B-CLL) but whose lymphocytes lacked CD5 expression. Haematological and clinical features of this CD5- series were compared with those of 333 CD5+ B-CLL patients from the same institute. No significant differences were observed regarding peripheral blood (PB) and bone marrow (BM) lymphocytosis, Hb level, platelet count, incidence of adenomegaly, hepatomegaly or splenomegaly or diffuse BM pattern. Due to an absence of nodal enlargements or to general clinical condition, lymph node biopsy was performed in only three patients, while spleen histology was examined in two cases following splenectomy. All histological results confirmed the clinical diagnosis of CLL. The distribution of the CD5- subjects according to the different staging categories proposed by Rai, Binet and Mandelli was similar to that of CD5+ subjects. Ten patients received standard chemotherapy with Chlorambucil (CHL) and Prednisone (PDN). All achieved partial remission, although one of these patients later died of disease progression; 80 months after diagnosis. We conclude that rare cases of CD5- lymphocytosis fulfilling all criteria for B-CLL may occur. Haematological and clinical features at presentation and the response to conventional treatment with Chlorambucil support our hypothesis of considering this disease as a less frequent subgroup of B-CLL.