Histological Factors Associated with Initial Bone Metastasis of Invasive Ductal Carcinoma of the Breast

Bone is one of the most common sites of recurrence of breast cancer. Therefore, it would be clinically very useful if breast cancers with a high probability of bone metastasis (BM) could be identified by histopathological examination of the primary lesions. To elucidate histological characteristics associated with predisposition to initial BM, we examined nine histopathological parameters in the primary lesions of 110 invasive ductal carcinomas (IDCs) of the breast with 0 to 3 regional node metastases. These cases had recurrence between 4 months and 10.1 years after the initial radical surgery. The first metastatic site was bone in 24 cases, whereas other sites were involved in 86 cases. IDCs growing in a strand growth pattern or with fibrotic focus (FF) had a significantly higher frequency of initial BM than those growing in a non‐strand growth pattern or without FF, respectively. Strand growth pattern was a significant predictor of the initial BM in multivariate analysis. In all 54 IDCs that developed BM during the follow‐up period, osteolytic metastasis was significantly more frequent in the group with FF than in that without FF. This study demonstrated that strand growth pattern and the presence of FF are significant histopathological factors associated with initial BM. The combination of those predictive factors along with prognostic factors may provide a useful approach to identify patients at high risk for initial BM, enabling early treatment for the recurrent cancer.