Alkaline phosphatase‐positive B cell lymphomas

Alkaline phosphatase (ALP) activity of 70 cases of non-Hodgkin's lymphomas of the B-cell type was studied. ALP activity was found in malignant lymphoma (ML), follicular, small cleaved cell (1/5 cases); ML, diffuse, small cleaved cell (3/13 cases); and mantle zone lymphoma (intermediate lymphocytic lymphoma) (2/2 cases). The ALP-positive neoplastic cells simultaneously displayed the characteristic immunophenotype of mantle zone (MZ) B lymphocytes of secondary follicle (SIg D +, BA-1 +, IL-2R+ and Leu-1+). All other B-cell lymphomas, including ML, follicular, mixed small cleaved and large cell (9 cases); ML, follicular, large cell (4 cases); ML, mixed small and large cell (7 cases); ML, diffuse, large cell (27 cases); and ML, small noncleaved cell (3 cases), were consistently negative for ALP. The present study indicates that ALP-positive lymphomas including follicular lymphomas and diffuse lymphomas may be neoplastic counterparts of ALP-positive MZ B lymphocytes.