Unusual presentation of a soft palate mass: A rare case report of solitary extramedullary plasmacytoma

INTRODUCTION: Plasmacytoma is a rare clonal neoplastic disorder of bone marrow that originates from plasma cells. It usually presents as a multiple myeloma (MM). Less than 5% of patients present with either a single bone lesion as a solitary bone plasmacytoma (SBP) or, even more rarely, as a soft tissue mass of monoclonal plasma cells representing a solitary extra medullary plasmacytoma (SEP). CASE PRESENTATION: We report a case of a 59-year-old man presenting with a mass of the soft palate evolving for a year. Physical examination showed an extension to the nasal cavity. Biopsy with immunohistochemical study demonstrated sheets of mononucleated plasmacytoid cells diffusely expressing CD138. The plasma cells showed monoclonal light chain Kappa. Further investigations did not show any other locations including bone and bone marrow. Thus, diagnosis of solitary extramedullary plasmacytoma of the soft palate was established. The patient was treated with chemotherapy with total remission on his one year follow-up. DISCUSSION: SEP may arise in any organ, either as a primary tumor or as part of a MM. Almost 90% of SEP arise in the head and neck, especially in the upper respiratory tract. Primary treatment for most patients is radiotherapy, but surgery may also be required, and multidisciplinary decision between surgeon, hematologist and radiotherapist is crucial for planning optimum care. CONCLUSION: SEP is an extremely rare condition which requires diagnostic and therapeutic management in the same level of MM. Prognosis is better than the two other forms (MM and SBP). (C) 2021 The Authors. Published by Elsevier Ltd on behalf of IJS Publishing Group Ltd.