Diagnostic dilemma in a case of gingival lesion plasma cell granuloma versus extramedullary plasmacytoma-resolved by immunohistochemistry: a case study

Plasma cell granuloma is a rare reactive tumor-like lesion composed of polyclonal plasma cells. It primarily affects the lungs but occurs in other anatomic locations such as orbit, paranasal sinuses, larynx, tonsils, ears, tongue, lip, oral cavity and gingiva. A 65-year old female presented with the chief complaint of swelling over the right upper gingiva and mobility of right upper 2^nd and 3^rd molar teeth since 3–4 months At histopathology due to presence of uniform population of plasma cells a histopathological diagnosis of plasma cell rich lesion was made with a differential diagnosis of extramedullary plasmacytoma and plasma cell granuloma. However, immunohistochemical staining for kappa and lambda chains showed a polyclonal process and antibodies to CD138 were strongly positive, confirming the diagnosis of plasma cell granuloma. The case describes a rare condition of plasma cell granuloma occurring at an unusual site. Authors also emphasize the importance of immunohistochemistry in differential diagnosis of plasma cell rich lesions.