Nodular histiocytic hyperplasia: A rare incidental finding that can be potentially misdiagnosed as malignancy

Abstract

Introduction: Nodular histiocytic hyperplasia is a rare benign condition that occur most commonly in body cavities such pleura, peritoneum, pericardium and in hernial sacs. Morphologically, it comprises nodular florid proliferation of histiocytes which can mimic malignant neoplasms such as metastatic carcinoma and mesothelioma. Therefore, it is essential to recognize this entity to prevent a potential diagnostic pitfall.Aim: To familiarize pathologists with a rare entity to prevent a potential diagnostic pitfall. Material and Methods: A case of inguinal hernia sac with incidental nodular histiocytic hyperplasia was studied for detailed histopathological examination and expression of immunohistochemical markers. Results: Running a wide panel of immunohistochemical stains revealed that the proliferative cells are positive for the histiocytic markers CD68 and CD163 but negative for epithelial and mesothelial markers. Conclusion: Nodular histiocytic hyperplasia is a benign condition characterized by proliferation of histiocytes that were believed previously to be of mesothelial origin. It is essential to recognize this entity as it can be potentially misdiagnosed as a malignant neoplasm.