This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nervous system, Subject name: Pathology
[{'content': 'Most common cause of leptomeningeal spread is from which of the following \nSelect and explain. \nA. Breast, B. Thyroid, C. Bone, D. Liver', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Leptomeningeal metastases, also know as carcinomatous meningitis, refers to the spread of malignant cells through the CSF space. These cells can originate from primary CNS tumors (e.g. This aicle has a focus on subarachnoid space involvement. Refer to <a class="internal" style="box-sizing: border-box; background: transparent; color: ; text-decoration-line: none;" href=" extramedullary metastases</a> for a discussion of leptomeningeal metastases in the spine. For other intracranial metastatic locations, please refer to the main aicle on <a class="internal" style="box-sizing: border-box; background: transparent; color: ; text-decoration-line: none;" href=" metastases</a>.', 'role': 'assistant'}]