Plasma cells in oral lesion: A clue to diagnosis or a diagnostic dilemma

OBJECTIVE: Plasma cells can just represent a part of host inflammatory response or form the cornerstone of diagnosis such as IgG4-related disease (IgG4RD) and plasma cell dyscrasias and sometimes create a diagnostic dilemma. The study aims to discuss a series of plasma cell lesions which we encountered in the oral cavity, discuss the diagnostic conundrum of plasma cell lesions. We also propose a working classification for their interpretation. MATERIALS AND METHODS: All plasma cell lesions affecting the oral and maxillofacial region were retrieved from the archives of the Department of Oral and Maxillofacial Pathology. The cases were analyzed on the basis of histomorphology and immunohistochemical markers along with clinical, imaging and laboratory findings. RESULTS: Thirteen (0.64%) of 2026 oral lesions were diagnosed with plasma cell lesions. Out of 13 cases, 9 were plasma cell gingivitis, 2 IgG4-RD, 1 plasma cell myeloma and 1 plasmablastic lymphoma. Representative case from each category is discussed along with one case of well-differentiated squamous cell carcinoma (WDSCC) masquerading as plasma cell dyscrasias. CONCLUSION: We discuss the practical difficulties faced during the diagnosis of these oral plasma cell entities along with a working classification and propose an efficient diagnostic scheme for the correct characterization of these lesions.