Prognostic significance of tumour infiltrating B lymphocytes in breast ductal carcinoma in situ

Aims Tumour‐infiltrating lymphocytes ( TIL s) are an important component of the immune response to cancer and have a prognostic value in breast cancer. Although several studies have investigated the role of T lymphocytes in breast cancer, the role of B lymphocytes ( TIL ‐Bs) in ductal carcinoma in situ ( DCIS ) remains uncertain. This study aimed to assess the role of TIL ‐Bs in DCIS . Methods and results Eighty DCIS cases (36 pure DCIS and 44 mixed with invasive cancer) were stained immunohistochemically for B lineage markers CD 19, CD 20 and the plasma cell marker CD 138. TIL ‐Bs density and localization were assessed, including relation to the in‐situ and invasive components. An association with clinicopathological data and patient outcome was performed. Pure DCIS showed a higher number of TIL ‐Bs and lymphoid aggregates than DCIS associated with invasion. In pure DCIS , a higher number of peri‐ and paratumoral TIL ‐Bs was associated significantly with large tumour size ( P = 0.016), hormone receptor ( ER / PR ) negative ( P = 0.008) and HER 2 + status ( P = 0.010). In tumours with mixed DCIS and invasive components, cases with high‐density B lymphocytes, irrespective of their location or topographic distribution, were associated significantly with variables of poor prognosis, including larger size, high grade, lymphovascular invasion, lymph node metastases, ER / PR ‐negative and HER 2 + status. Outcome analysis showed that pure DCIS associated with higher numbers of B lymphocytes had shorter recurrence‐free interval ( P = 0.04); however, the association was not significant with the CD 138 + plasma cell count ( P = 0.07). Conclusion Assessment of TIL ‐B cells based on location and topographic distribution can provide prognostic information. Validation in a larger cohort is warranted.