Bone Marrow (BM) is poorly understood from the point of view of the prognostic role of hematopoietic cells and subpopulations of lymphocytes in patients with Breast Cancer (BC). In recent years, more attention has been paid to the study of the innate immune system, which includes B-lymphocytes. They produce IgM antibodies, which play an important role in the induction of apoptosis.

Study was carried out in 107 BC patients’ stage I‒II. Adjuvant chemotherapy ‒ 65.4% of patients, radiation therapy ‒ 49.8%, hormone therapy ‒ 84% of patients. Her2/neu"-" 80%, Her2/neu"+"-18%, TNBC-12%. The duration of the follow-up period after surgery was 8-years. Multiparameter flow cytometry was used, FACSCANTO II. Studies of BM lymphocyte subpopulations were carried out in the gate of CD45++ cells: CD19, CD20, CD5, CD38, CD10, CD45, HLA-DR, CD27. Radical resection -38.3% of patients, mastectomy ‒ 59.7%.

B1-cells was higher in B-Her2"+", stage IIA, with 2 affected lymph nodes. B1-cells correlated with plasma cells. The total percentage of B-cells in BM was significantly associated with the prognosis of BC. B1 cells were associated with progression-free and disease-free survival. Disease progression was observed at low levels of B1 cells. In cases more than 10% B-lymphocytes in the BM of BC patients’ Overall Survival (OS) rates were more favorable (p = 0.01). Especially for BC with a high Ki-67. Disease progression was observed in 1/3 of BC patients with low levels of B1 cells. CD38 expression on B-cells was a prognostically favorable factor: the role is realized during 5–10-years of follow-up after surgery. Level CD38+ B-cells more than 10% correlated with high OS (p = 0.02). The presence of CD10+CD19+ B-lineage precursors was associated with a more favorable prognosis (OS, the threshold level 12%, р = 0.04). The prognostic role of the CD10 antigen was realized when patients were observed for more than 5-years.

Total relative number of (more than 10%) of BM CD19+ cells were significantly related to OS in BC. B-cell precursors and CD38+ B-cells were associated with favorable prognosis. Prognostic role of B-lineage precursors and CD38- positive cells was in the periods of 5–10 years after surgery.