Abstract. Multiple myeloma is a primary malignancy of bone marrow characterized by the clonal proliferation of plasma cells and production of monoclonal immunoglobulin. The disease occurs more frequently in males, with the average age at diagnosis being ~60 years. The first manifestation of multiple myeloma is varied and depends on the sites and extent of involvement. The predominant clinical symptoms of multiple myeloma are associated with bone pain and renal dysfunction. Neoplastic cells usually produce large amounts of monoclonal immunoglobulin light or heavy chains that can be detected in serum or urine, while plasmacytoma may be identified on marrow biopsy. The present study reported on the case of a 69-year-old male patient presenting with a complaint of a painful lesion in the left maxilla. Physical examination, imaging, laboratory investigations and biopsy were conducted, confirming the diagnosis of multiple myeloma. The results obtained suggest that the dentist should address oral manifestations as first indications of multiple myeloma. IntroductionMultiple myeloma involves the clonal proliferation of plasma cells based in the bone marrow, with various degrees of differentiation (1). Neoplastic cells usually produce large amounts of monoclonal immunoglobulin light or heavy chains that can be detected in serum or urine (2). Although multiple myeloma is the most common primary bone cancer in adults, in ~95% of cases, it involves several bones (3).The etiology of this disease remains to be determined. However, some occupations, exposure to certain chemicals, overdose irradiation, viruses and genetic factors are considered to be etiologic factors (4).Myeloma is slightly more prevalent in males and individuals of African-American descent (5). In western countries, the disease is more prevalent in males, with a median and average age at diagnosis of 66 and ~60 years, respectively (6). By contrast, the median and average age at diagnosis is 57 and 55-65 years, respectively (7). The first manifestations that usually present at diagnosis include bone pain (58%), fatigue (32%) and weight loss (24%) (6). The diagnosis of myeloma is usually confirmed by the demonstration of a monoclonal protein (M-protein) in the serum or urine and/or lytic lesions on X-ray together with histological confirmation of a malignant proliferation of plasma cells (8). Treatment involves mainly irradiation, chemotherapy, autologous stem cell transplantation. Prognosis is determined via risk classification by the International Staging System (ISS) (9).The present study reports a case of painful ulcer-like maxillary mass with multiple myeloma, which was diagnosed based on biopsy of the oral lesion. Case reportA 69-year-old male patient presented with a chief complaint of a painful ulcerated lesion in left maxilla, for ~1 month. Although the patient was treated with antibiotics and cortisol, the lesion was non-healing and became enlarged and painful, resulting in restriction of mouth opening and a weight loss of 4 kg during the month he was ...