Abstract P1-05-31: A single center retrospective analysis of 259 cases of metaplastic breast cancer
Authors: Liu Douwaner , Chen Jiajian , Hao Shuang , Xiu Bingqiu , Zhang Qi , Zhang Liyi , Liu Guangyu , Shao Zhimin , Wu Jiong 
Published: March 2023

Abstract
Introduction: Metaplastic breast cancer (MBC) is a rare breast tumor.WHO histological classification of breast tumors in 2019 divided MBC into the following seven types: low-grade adenosquamous carcinoma, fibromatoid metaplastic carcinoma, squamous cell carcinoma, spindle cell carcinoma, metaplastic carcinoma with mesenchymal differentiation, mixed metaplastic carcinoma and myoepithelial carcinoma. Based on single center data, this study intends to conduct a detailed analysis of the clinicopathological features, treatment and prognostic factors of MBC. Methods:We collected 259 MBCs treated in our center from 2006 to 2022. The patient’s age, histological type, image feature, tumor size, lymph node metastasis, tumor stage, immunohistochemical information, surgical plan and systemic adjuvant therapy were summarized and considered to explore the factors affecting the overall survival rate (OS) and disease-free survival rate (DFS). T-test and chi-square test were performed on the data. P&lt; 0.05 showed that the difference was statistically significant. Kaplan-Meier survival was used to analyze the long-term efficacy. Results: The incidence rate of MBC in breast cancer patients in our center is about 0.5%. They included 105 cases of squamous cell carcinoma (40.5%), 49 cases of mixed metaplastic carcinoma (18.9%), 41 cases of spindle cell carcinoma (15.8%), 27 cases of metaplasia carcinoma secreting matrix (10.4%), 6 cases of metaplastic carcinoma with mesenchymal differentiation (2.3%), 6 cases of myoepithelial carcinoma (2.3%), 3 cases of low-grade adenosquamous carcinoma (1.2%), 1 case of fibromatoid metaplasia carcinoma (0.4%) and 21 cases of unknown (8.1%). MBC were mainly three negative subtypes, which were 204 cases (78.8%), 41 cases (15.8%) luminal subtypes and 14 cases (5.4%) HER2 positive subtypes. There was no significant difference in the distribution of breast cancer subtypes among different histological types of MBC. There were 63 cases (24.3%) in clinical stage I, 171 cases (66.0%) in stage II, 23 cases (8.9%) in stage III and 2 cases (0.8%) in stage IV. 58 patients underwent core needle biopsy, of which only 7 (12.1%) reported histological types consistent with MBC. Among 154 patients with molybdenum target reports, 59 of them (38.3%) had malignant calcifications. The diagnostic coincidence rates of MRI, ultrasound and molybdenum target were 90.0%, 85.1% and 74.7% respectively. 258 cases of MBC received surgical treatment, including 183 cases of total mastectomy (70.9%), 53 cases of breast conserving surgery (20.5%) and 22 cases of quadrant resection (8.5%); 132 patients (51.2%) underwent axillary lymph node dissection and 93 patients (36.0%) underwent sentinel lymph node biopsy. 24 patients (9.3%) received neoadjuvant chemotherapy, of which only 2 (8.3%) achieved pathological complete remission. 56 patients (21.6%) received adjuvant radiotherapy, with a median of 25 times. 167 patients (64.5%) received adjuvant chemotherapy, and anthracycline sequential paclitaxel was the most commonly used regimen. The median follow-up was 31 months. The five-year DFS was 82.0%, and the five-year OS was 89.4%. Through Cox regression analysis, it was found that patients’ N stage (P=0.036) and receiving anthracycline sequential paclitaxel adjuvant chemotherapy (P=0.004) were independent prognostic factors. Conclusion: The histological types of MBC are complex. MRI is of high value in diagnosis. Conventional CNB is difficult to meet the needs of pathological tissue classification. Patients without lymph node metastasis and receiving anthracycline sequential paclitaxel adjuvant chemotherapy are associated with better prognosis. Through multidisciplinary standardized diagnosis and treatment, there is no significant difference between the prognosis of MBC and the common types of breast cancer. Keyword: metaplastic breast cancer; pathological characteristics; imaging; treatment; prognosis.
Citation Format: Douwaner Liu, Jiajian Chen, Shuang Hao, Bingqiu Xiu, Qi Zhang, Liyi Zhang, Guangyu Liu, Zhimin Shao, Jiong Wu. A single center retrospective analysis of 259 cases of metaplastic breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-05-31.