J.J. Zou1, J. Den2, R. Shah1, G. Golovko3, J. He4, N. Nelson2, V. Klimberg2,5 1University Of Texas Medical Branch, School Of Medicine, Galveston, TX, USA 2University Of Texas Medical Branch, Surgery, Galveston, TX, USA 3University Of Texas Medical Branch, Pharmacology and Toxicology, Galveston, TX, USA 4University Of Texas Medical Branch, Pathology, Galveston, TX, USA 5MD Anderson Cancer Center at Houston, Department of Breast Oncology, Houston, TX, USA
Introduction: Metaplastic breast carcinoma (MBC) is a rare neoplasm accounting for <1% of all breast cancer (BC). It is characterized by histologic and molecular heterogeneity with differentiation into subtypes including squamous cells and/or mesenchymal-like elements, such as spindle, chondroid, and osseous. It is therapeutically challenging and has a worse prognosis than other BC types. Little is known about its different subtypes. Our research evaluated the clinical characteristics and survival outcomes of the different subtypes of metaplastic BC.
Methods: This was a retrospective study over 13 years (2010 – 2023) using the TriNetX database. A total of 517 diagnosed with MBC were identified in the database. The cohort was further queried by subcategories of MBC (adenosquamous carcinoma, epithelial-myoepithelial carcinoma, adenocarcinoma with squamous metaplasia, adenocarcinoma with cartilaginous and osseous metaplasia, adenocarcinoma with spindle cell metaplasia, metaplastic carcinoma, not otherwise specified (NOS), carcinoma, NOS, myoepithelial carcinoma, and carcinosarcoma, embryonal). Data on TNM, stage, treatments (radiation oncology, mastectomy, excision, chemotherapy), and biomarkers (ER, PR, HER) were analyzed. A Kaplan-Meier Analysis was used to compare overall survival between metaplastic carcinoma and carcinosarcoma.
Results: Metaplastic carcinoma, NOS, included 417 patients (77.7%); carcinosarcoma, NOS, included 46 patients (8.6%); adenosquamous carcinoma included 21 patients (3.9%); adenocarcinoma with cartilaginous and osseous metaplasia included 13 patients (2.4%) and the other subtypes all had <10 patients. The mean age of all MBC subtypes was 68, with a standard deviation of 14. It has the highest prevalence in whites (62.6%) followed by black/African American (20.5%). They are most likely to be malignant (89%), in stage 2 (38%), T2 (42%), N0 (66%), M0 (69%), and triple negative. Chemotherapy (54%) and mastectomy (44%) were the most common treatments. Carcinosarcoma had a median survival of 5.5 years and metaplastic carcinoma had a median survival of 6.4 years.
Conclusion: Metaplastic breast carcinoma has a variety of subtypes, with carcinosarcoma being the most common. This is followed by adenosquamous carcinoma and adenocarcinoma with cartilaginous osseous metaplasia. Despite its poor prognosis, little research on MBC is conducted on the different subtypes, which warrants further investigation.