Aim. The main objective of this study was the comparative investigation of diverse lipid second messenger (LSM) generation by human peripheral blood lymphocytes (HPBL) at different (5, 10, 30 and 60 s) time points of cell co-stimulation by anti-CD3 and anti-CD28 monoclonal antibodies in norm and breast cancer (BC). Methods. Ficoll-Hypaque gradient centrifugation. Results. The data obtained indicate that some mechanisms of LSM generation/utilization in stimulated crude HPBL were significantly altered in BC compared to norm. Particularly, the reliable generation of arachidonyl-1,2-diacylglycerol (1,2-DAG) at the initial step (5 s) of cell stimulation observed in norm was depressed in BC and reached the value below the basal level in unstimulated cells. It is important that the disturbances in 1,2-DAG formation in HPBL obtained from patients with BC were identical with those observed earlier in other forms of cancer. Conclusions. We conclude that the regularities revealed are common characteristics for all the types of malignancy studied and can be used as additional testing parameters for cancer definition and individual correction of the chemotherapy programs for disease treatment.