Breast carcinoma (BC) is one of the most common osteotropic tumors. The subset of BC patients with isolated bone metastasis (IBM) forms a clinically distinct group and often has a favorable clinical outcome as compared to others with metastatic BC. We analyzed all BC patients with distal organ metastasis in our institution between 1997 and 2003 (N = 198) to identify the clinicopathologic features of BC with IBM and compare them to those with metastasis to other sites. We found that 63% of BC patients with advanced disease had bone metastases, and 44% of those were IBM. The proportion of cases with IBM that expressed estrogen receptor and/or progesterone receptor (47/52; 90%) was significantly higher than those with non-bone metastases (P < .0001) and than those with multiple metastases involving bone (P < .0001). The distribution of BC molecular subtypes in cases of IBM was again significantly different from that of the remainder. By univariate and multivariate analysis of the clinicopathologic factors examined, only estrogen receptor and progesterone receptor status of the primary tumor was predictive for IBM. The median survival after diagnosis of metastatic disease was significantly longer in cases with IBM than that of any other group. Our results indicate that the diversity in receptor expression patterns not only reflects the biological diversity of mammary tumors but may also predict their metastatic potential and thus could potentially be used in surveying women patients with nonmetastatic disease.
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