Osteoclast-like giant cells in invasive breast cancer predominantly possess M2-macrophage phenotype.

Breast carcinoma with osteoclast-like giant cells (OGCs) is a rare tumor; however, their clinicopathological aspects remain unclear. We described the clinicopathological characteristics of 8 patients with breast carcinoma with OGCs. Immuno-phenotypes of the OGCs were comparatively examined with that of foreign body giant cells (FBGCs) in 4 cases of granulomatous reaction (GR) without cancerous elements. In most cancers, tumors displayed cribriform and tubular growth patterns. Three cases showed moderate to high nuclear grade, while all the other tumors had low nuclear grade. Six patients were estrogen receptor (ER) positive, while triple negative phenotype was identified in 2 patients. During the follow-up period, 1 patient had local recurrence of the tumor, and all the patients remained alive. All OGCs and FBGCs expressed CD68, a pan-macrophage marker. OGCs in all the breast cancers showed moderate to high expression of CD163 - a marker of M2-macrophage with pro-tumoral function - whereas its expression in FBGCs was low to moderate (p=0.04). CD86 - a marker of M1-macrophage with a tumoricidal activity - was positive in the OGCs of 3 breast cancers, and in the FBGCs of 3 GR cases (p=0.15). The expression of CD163 was significantly higher than that of CD86 in the OGCs of breast cancer (p<0.001), whereas they were comparable in the FBGCs of GR (p=0.79). In summary, we found that breast carcinoma with OGCs mostly exhibited cribriform and tubular growth pattern, ER positivity, and predominantly possessed the M2-macrophage phenotype. However, the clinical significance of OGCs in breast cancer needs to be elucidated in further studies involving a larger number of cases.