Plasma cell myeloma of the mandible: a case report

Abstract

Plasma cell myeloma (PCM, also known as multiple myeloma [MM]), is a bone marrow malignant proliferation of monoclonal plasma cells accompanied by serum or urine M protein. In contrast, solitary plasmacytoma of bone (SPB) is a localized monoclonal proliferation of plasma cells without bone marrow involvement. In the head and neck region, PCM and/or SPB present in the jaws, mostly in the posterior mandible. Typically, with nonspecific and ambiguous symptoms. Microscopically, these tumors have to be separated from florid inflammatory plasma cell-rich lesions. The aim of this report is to present a case of PCM of the mandible. A 59-year-old female was referred for evaluation of an asymptomatic mandibular lesion. Intraoral examination showed no expansion of the affected area. A panoramic radiograph revealed a circumscribed, noncorticated radiolucency in the left posterior body of the mandible. The patient’s medical history was noncontributory. A biopsy was obtained, and the tissue was fixed in 10% buffered formalin. Microscopic examination showed sheets of densely infiltrative atypical cells with eccentric nuclei and clockface chromatin displaying plasma cell morphology. Immunohistochemical examination showed CD138 and lambda light chain positivity. Kappa light chain, CD3, CD20, and MPO were negative. In view of the patient’s unremarkable past medical history, the diagnosis rendered was consistent with solitary plasmacytoma. However, the patient was referred to an oncological center for a complete work-up and a diagnosis of multiple myeloma was established. Clinical history, immunohistochemical stains, and laboratory studies are essential for the diagnosis of PCM.