Synchronous pulmonary adenocarcinoma and primary leptomeningeal large B-cell lymphoma-Diagnostic challenge in cerebrospinal fluid: A brief report.

Lung cancer is one of the most common causes of cancer-related deaths worldwide. During or after the treatment of lung cancer, patients might develop another malignant neoplasm. To our knowledge, synchronous pulmonary adenocarcinoma and leptomeningeal large B-cell lymphoma have not been reported in the literature. Herein, we report the first case of synchronous pulmonary adenocarcinoma and primary leptomeningeal lymphoma, which is challenging in cytological diagnosis using cerebrospinal fluid (CSF). Knowledge of this rare situation by cytopathologists might avoid misdiagnosis or erroneous tumor classification during the cytological diagnosis of CSF in the future.