Intravascular carcinomatosis of central nervous system due to metastatic inflammatory breast cancer: A case report.

Central nervous system (CNS) involvement by metastatic cancer is well-recognized and typically presents with multifocal solid tumors within the brain parenchyma or leptomeningeal dissemination. We describe herein a histologically very rare case of CNS metastasis in a 52-year-old woman who presented with mental status changes. Post mortem examination revealed extensive CNS involvement by metastatic inflammatory breast carcinoma, characterized by the presence of single tumor cells diffusely present within capillaries without parenchymal or perivascular invasion, and acute ischemic changes/infarcts bilaterally involving multiple areas. The cancer cells were found predominantly in the cerebral cortices and deep gray matter structures. Pre-mortem magnetic resonance and CT imaging of the brain did not identify metastatic cancer; however, widespread ischemic changes (i.e. brain infarcts) were identified. Inflammatory breast carcinoma is well-known to have a predilection for spread through lymphovascular spaces. Post mortem examination revealed tumor involvement of bilateral lungs, heart and bladder, with sinusoidal spread in the liver and lymph nodes and prominent involvement of the splenic red pulp in addition to extensive vascular involvement of the brain and spinal cord without a discrete mass, despite the presence of widely metastatic disease. The tumor cells in the CNS were strongly immunoreactive for pancytokeratin, E-cadherin, cytokeratin-7, epithelial membrane antigen and CAM 5.2. This unique histologic pattern of tumor spread is considered to represent "intravascular carcinomatosis" in the CNS, and most likely the cause of the patient's widespread ischemic injuries.