Introduction & Objective This report highlights an unusual presentation of skin metastasis of inflammatory breast cancer that resembles a rare condition called Carcinoma en Cuirasse (CeC). CeC was first described by anatomist Alfred Velpeau in 1838 when he observed how the coalescing nodules and diffuse sclerodermoid induration found on the chest and abdomen in CeC resembled the medieval steel breastplate or a cuirasse. Case Presentation A 62-year-old female presented to the emergency department for evaluation of a palpable left breast mass and concurrent skin lesions for the past 5 months. Based on the erosion of the nipple, chest CT, as well as core needle and skin biopsy, a diagnosis of stage IV (cT4d, cN3, cM1) ER+, PR-, HER2/neu- advanced/inflammatory breast carcinoma was made. The patient underwent a 20-week course of neoadjuvant chemotherapy followed by 25 treatments of neoadjuvant external beam radiotherapy (EBRT) with a total dose of 5000cGy to the left breast and the regional lymph node due to disease progression after 4 cycles of neoadjuvant chemotherapy. She proceeded to bilateral modified radical mastectomy and bilateral lymph node involvement was found, and later disease progressed with skin involvement outside the EBRT treatment field. Additional 25 treatment of palliative radiotherapy was utilized with another 5000cGy, followed by 2 months of chemotherapy to provide better palliation and quality of life. Upon completion of therapy, a unique skin metastasis pattern was noticed. Shortly afterward the patient passed away from severe sepsis secondary to multiple wounds infected by drug-resistant Pseudomonas aeruginosa followed by Clostridium difficile colitis. Conclusion This case shows clinical characteristics of Carcinoma en Cuirasse and provides important considerations for more research to be done to highlight the unique pattern of skin metastasis following radiation and the potential use for radiation to treat chemotherapy-resistant skin metastasis from recurrent invasive breast carcinoma.

Citation Format: Chung-Tang Liu, Keri Lanier. Carcinoma en Cuirasse Secondary to Locally Advanced Breast Carcinoma: a case report [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 P1-10-06.