B-cell markers on lymphoblasts in acute lymphoblastic leukaemia.

Acute lymphoblastic leukaemia (ALL) has been shown to be of T-cell or undefined origin. We now describe a man of 75 years with ALL of apparent B-cell origin. Thirty-five cases of untreated ALL were studied for B-cell and twenty-four of them also for T-cell markers. In the patient with ALL of B-cell type the lymphoblasts carried mu-lambda suggesting a monoclonal origin of the malignant cells. The remaining thirty-four cases exhibited relatively normal proportions and numbers of B-lymphocyte subpopulations. Four of the twenty-four cases studied for T cells had ALL of T-cell origin. In the remaining twenty patients T lymphocytes were present, but generally in decreased numbers. The one patient with ALL of B-cell type was an elderly man, while the other thirty-four cases of T-cell or undefined origin occurred in children or younger adults. This suggests that in older patients ALL, like other lymphoid malignancies, may more often be of B-cell origin.