In the cerebrospinal fluid (CSF), the demonstration of malignant cells by cytological examination is currently the gold standard for the diagnosis of leptomeningeal carcinomatosis (LC). However, a positive cytology is observed in only 50–60% of patients with LC and highly dependent on pre-analytical factors. The hematology laboratory could provide an immediate and accurate diagnosis, but diagnostic sensitivity is not always optimized once the sample is received. We hereby report a 49-year-old woman with a 3-year grade III invasive ductal carcinoma who was admitted to the emergency department due to headaches, nausea, and vomiting. The CSF revealed pleocytosis with suspicious high fluorescent cells on the hematology analyzer concomitantly with biochemical alterations. Cytomorphological examination confirmed tumor cells, thus diagnosing a leptomeningeal metastasis of her breast cancer. The patient was eventually transferred to palliative care. Cytological examination is a valuable tool for a rapid diagnosis of LC if diagnostic performance is optimized. In addition to repeated CSF collections with a sufficient volume (5–10 mL), this could be reached by processing the CSF as soon as possible, taking into account the fluorescence information from the analyzer, proceeding systematically to microscopic examination even with normal CSF white blood cell count, and providing quality improvement of the staff to identify malignant cells.

Immune-related adverse events including cardiac toxicity are increasingly described in patients receiving immune checkpoint inhibitors. We described a malignant pericardial effusion complicated by a cardiac tamponade in an advanced non-small cell lung cancer patient who had received five infusions of atezolizumab, a PDL-1 monoclonal antibody, in combination with cabozantinib. The definitive diagnosis was quickly made by cytology examination showing typical cell abnormalities and high fluorescence cell information provided by the hematology analyzer. The administration of atezolizumab and cabozantinib was temporarily discontinued due to cardiogenic hepatic failure following cardiac tamponade. After the re-initiation of the treatment, pericardial effusion relapsed. In this patient, the analysis of the pericardial fluid led to the final diagnosis of pericardial tumor progression. This was afterwards confirmed by the finding of proliferating intrapericardial tissue by computed tomography scan and ultrasound. This report emphasizes the value of cytology analysis performed in a hematology laboratory as an accurate and immediate tool for malignancy detection in pericardial effusions.