Plasma cell neoplasia is a lymphoid neoplastic proliferation of B cells. This denomination encloses multiple myeloma (MM), solitary bone plasmacytoma and extramedullary plasmacytoma. MM consists of a clonal proliferation of plasma cells based in the bone marrow, with various degrees of differentiation. Neoplastic cells usually produce great amounts of monoclonal light or heavy chains of immunoglobulin that can be detected in serum or urine. The disease is more frequently in men and the average age at diagnosis is about 60 years. The diagnosis is established by blood and urine exams and medullary biopsy. Patients may present renal failure, bone pain, fatigue, recurrent infections and nervous system dysfunction. Oral manifestations may be the first sign of MM, highlighting the importance of the dentist in the early diagnosis of the disease. Treatment involves mainly irradiation and chemotherapy and the prognosis is generally poor. This paper reports a case of a 65 years old black female who had a complaint of a painful mass in the maxilla that prompted a MM diagnosis.