Cytologic diagnosis and differential diagnosis of histiocytic signet ring cells in effusion specimens

Our study provides a detailed characterization of benign histiocytic signet ring cells in effusion cytology. The differential diagnosis of histiocytic signet ring cells is broad. The most important differential diagnoses are metastatic adenocarcinoma and epithelioid signet ring cell mesothelioma. The accurate diagnosis is critical for the appropriate clinical management of the patient. Cytopathologists should be aware of the diagnostic pitfalls of benign histiocytic signet ring cells in effusion samples in daily practice.