Abstract: Background and purpose: The incidence of bone metastasis in advanced breast cancer (BC) is more than 70%, and decalcification of bone tissue is a technical difficulty. This study aimed to explore the clinical features of BC with bone metastasis and more suitable methods for decalcification of bone tissue. Methods: Clinical data of patients with pathological diagnosis of BC with bone metastases from January 2012 to January 2018 were collected and analyzed for clinical characteristics. We compared the differences in bone morphology and structure between tissues treated with modified ethylenediaminetetraacetic acid (EDTA) decalcification and acid decalcification. We examined the consistency of endocrine receptors between primary and metastatic bone tissues. Then the immunohistochemistry (IHC) results of estrogen receptor (ER), progesterone receptor (PR) and Ki-67 were compared between the two groups. Finally, we analyzed the survival differences of ER and PR status in patients. Results: Among 116 patients including 41 cases of modified EDTA decalcification and 75 cases of acid decalcification, 91.4% were osteolytic bone metastases, 80.1% of bone metastases ranged from 4 to 20, and 81.9% had skeletal-related events (SRE). The consistency of ER in patients with bone metastases from modified EDTA decalcification group was 95.1%, which was significantly higher than that in acid decalcification group (69.3%) (P<0.05). The positive rates of ER, PR and Ki-67 in the modified EDTA decalcification group was significantly higher than those in the acid decalcification group (P<0.05). The mean survival of ER + patients ［(41.09±4.26) months］ was significantly longer than that of ER - patients ［(25.81±5.71) months］(P<0.05). Conclusion: Bone metastases in BC are most likely multiple osteolytic lesions, and the incidence of SRE is high. The modified EDTA decalcification method is superior to the acid decalcification method and more suitable for decalcification and IHC of bone tissue.

Key words: Ethylenediaminetetraacetic acid decalcification, Acid decalcification, Breast cancer, Bone metastasis, Bone tissue biopsy