Abstract PO5-17-07: MUCINOUS BREAST CARCINOMA: REAL WORLD DATA IN A REFERENCE CENTER IN SÃO PAULO
Authors: De Figueiredo Marina Fleury , Mattar Andre , Cavagna Felipe , da Silva Ana Lígia Minatel , Nadai Rafaella , de Oliveira Juliana Medeiros , de Figueiredo Luma Fleury 
Published: May 2024

Abstract
BACKGROUND: Mucinous breast carcinoma (MC) is a subtype of invasive carcinoma that corresponds to 1 to 6% of all types of breast cancer. It occurs when the mucinous component accounts for more than 50% of the tumor producing extracellular mucin in large scale. Mucin is a complex carbohydrate engaged in processes such as epithelial differentiation, adhesion modulation and cell signaling. Along with other special types of breast neoplasia, MC appears to have an unique behavior and, since it’s low amount of cases, a detailed clinical evaluation has been difficult. OBJECTIVES: To describe the profile of patients with breast MC that were treated in a reference center in São Paulo, Brazil as well as evaluate its management and outcomes. METHODS: A descriptive longitudinal observation study conducted at São Paulo’s Women’s Health Reference Center - Hospital da Mulher from July 2022 to January 2023, based on 192 medical records of patients diagnosed with MC from 2003 to 2018. RESULTS: 192 patient’s records were included. The age range was 31-93 years, out of which 74,3% of the patients were older than 50 when diagnosed. 48,7% identified as white and 43,7% showed earlier diagnoses of systemic hypertension. The time range between diagnosis and first treatment was 4,5 months. Out of the histopathological features, the nuclear grade was 3 in 69 patients (34,6% of the cases), and histological grade 1 in 52,7%. About pathological staging, the size of the tumors went form 0,5 to 9,5 cm, with an average of ± 4,7cm, the majority of them showed positive ER (89,4%), negative PR (85%), and were negative for Her-2 (76%). Greater number of patients (92,4%) went through both clinical and surgical treatment. Only 15 (7,5%) had isolated clinical treatment. 31% of the patients received systemic chemotherapy treatment, 25% of those were neoadjuvant. 81,9% of patients received aromatase inhibitor and only 17% radiotherapy. Distant metastasis were diagnosed in 27 patients (13,5%) and the local recurrence was observed in 15,3%. Out of distant metastasis, pulmonary type was more prevalent, registered in 45,7% of patients, followed by osseous (22,88%) and hepatic (14,2%). 33 patients (16,5%) progressed to death, however, the specific cause was not determined. CONCLUSION: MC is a rare subtype of breast cancer, more prevalent in post-menopausal and white women. Frequently shows low histological grade and positive hormonal receptors, which reinforces the idea of a indolent behavior. The treatment is mostly surgical, with adjuvance if necessary. Metastasis are infrequent and knowing the profile of patients with MC, as well as it’s behavior, allows the better management when facing this diagnosis.
Citation Format: Marina Fleury De Figueiredo, Andre Mattar, Felipe Cavagna, Ana Lígia Minatel da Silva, Rafaella Nadai, Juliana Medeiros de Oliveira, Luma Fleury de Figueiredo. MUCINOUS BREAST CARCINOMA: REAL WORLD DATA IN A REFERENCE CENTER IN SÃO PAULO [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-17-07.