Metastatic Adenoid Cystic Carcinoma of the breast at diagnosis

Introduction: adenoid cystic carcinoma of the breast is a rare lesion among breast carcinomas, representing less than 0.1% of breast cancer cases. Generally indolent behavior with rare lymph node involvement and metastases. Case Report: 76-year-old patient complaining of a lump in her right breast that had appeared 8 months ago. Ultrasonography showed a heterogeneous image of 3.9/2.4/3.7cm. On palpation, there was an 8cm nodule and mobile and fibroelastic axillary lymph nodes. A core needle biopsy was performed with an anatomopathological result of triple-negative grade 2 adenoid cystic carcinoma. Screening demonstrated two 1.1cm pulmonary nodules with soft tissue density suggesting metastasis. Abdominal tomography demonstrated liver nodules suggestive of secondary implants. The PET scan confirmed uptake in the lung and liver nodules, in addition to lytic lesions in S3. Liver biopsy confirmed implantation of adenoid cystic carcinoma. Chemotherapy was started with a regimen of Carboplatin, Paclitaxel and Pembrolizumab. After the third cycle of chemotherapy, the breast was reevaluated without showing any tumor reduction. The metastases also did not show regression, and treatment was interrupted. The patient evaded the service until January 2024, when he returned complaining of pain in the right hip and difficulty walking. Chest and hip tomography showed an increase in lung lesions and the appearance of lytic metastasis in the iliac bone. The patient refused to undergo radiotherapy and in May 2024 she developed liver failure and death. Discussion: In the metastatic setting, the regimens of choice are based on anthracyclines and taxanes with reports of little response. Our report aims to contribute to the introduction of a new group of drugs (pembrolizumab) associated with the standard taxane regimen, demonstrating that this type of tumor really has a difficult response to chemotherapy agents and that there is little that can be done in the setting of multiple metastases.