Histology: immature mononuclear cells in tissue and lymphoblast-like in bone marrow or blood. Areas of lymphoma show a monotonous proliferation with diffuse infiltration into T-zone areas.
Immunophenotype:
(1) CD56 positive
(2) negative for surface CD3 (cytoplasmic CD3 may be present)
(3) negative for T-cell markers: CD8, T cell receptor (TCR) gene
(4) negative for B-cell markers: CD20, surface immunoglobulins
(5) negative for myelomonocytic markers: CD13, CD14, CD15, CD25, CD33, myeloperoxidase
(6) often positive for CD4, CD7, and/or CD43
(7) often positive for HLA-DR
(8) may be positive for TdT and/or CD34
(9) may be positive for CD16 (an NK cell marker)
For diagnosis the cells must show >= 1 NK cell antigen and be negative for all B-cell, T-cell, and myelomonocytic antigens.
Criteria for the diagnosis of leukemia - one of the following:
(1) > 30% tumor cells in bone marrow
(2) > 30% tumor cells in peripheral blood
If the proliferation was not leukemia, then it was termed lymphomatous.
