Isolated Leptomeningeal Carcinomatosis in Triple-Negative Breast Cancer: A Case Report.

Introduction: Leptomeningeal carcinomatosis (LC) is a rare but devastating complication that can arise from various cancers, particularly breast cancer. Case Presentation: We present the case of a female patient with early onset triple-negative breast cancer (TNBC) who developed isolated LC shortly after completing neoadjuvant and adjuvant treatment. The patient had no evidence of parenchymal brain metastases at the time of LC diagnosis. Our patient received treatment with both intrathecal and systemic chemotherapy. While there was a brief period of clinical improvement, she subsequently developed brain metastases and ultimately succumbed to its complications. Isolated LC is an extremely rare occurrence, as leptomeningeal metastasis usually presents concurrently with parenchymal metastases. This case is particularly notable for the development of LC as the sole site of metastasis following completion of adjuvant therapy. Conclusion: This case highlights the importance of recognizing LC in patients with TNBC, even in the absence of other metastatic sites. Our report, along with a concise review of current literature, aims to improve recognition and treatment options for this rare and clinically heterogeneous entity.