High density of CD204‐positive macrophages predicts worse clinical prognosis in patients with breast cancer

Recent studies have indicated the clinical significance of tumor‐associated macrophages (TAM) in several malignant tumors including breast cancer. Although recent studies have focused on CD68‐positive or CD163‐positive TAM in breast cancer, no study has investigated the significance of CD204‐positive TAM in breast cancer. We found that CD204 expression on macrophages was evaluated following stimulation with the conditioned medium (CM) of breast cancer cell lines. Paraffin sections of 149 breast cancer samples which were diagnosed as invasive ductal carcinoma were immunohistochemically analyzed for CD68, CD163 and CD204 expression. The results of analyses indicated that a high number of CD204‐positive TAM was associated with worse clinical prognoses, including relapse‐free survival, distant relapse‐free survival and breast cancer‐specific survival; however, neither the numbers of CD68‐positive or CD163‐positive TAM were associated with clinical courses. Of the clinicopathological factors investigated, estrogen receptor, Ki‐67 index, hormone subtype, and histological grade were significantly related to the increased number of CD163‐positive and CD204‐positive TAM. These data indicate the clinical significance of CD204‐positive TAM in breast cancer progression and CD204 is a marker for predicting clinical prognosis in breast cancer.