Medication-related osteonecrosis of the jaw in a patient with multiple myeloma: an unusual case with tumor in the surgical specimen.

Multiple myeloma is characterized by a neoplastic proliferation of plasma cells primarily in the bone marrow. Neoplastic plasma cells stimulated osteoclasts, and destroy bone tissue, causing bone pain, pathological fractures, paralysis due to spinal cord compression, and hypercalcemia. Bisphosphonates are used as supportive therapy in the management of multiple myeloma. Medication-related osteonecrosis of the jaw (MRONJ) is a well-known complication of treatment with bisphosphonates, denosumab, and other drugs, such as anti-angiogenic agents and novel anti-cancer drugs. We report MRONJ in a patient with multiple myeloma, especially an unusual case with tumor in the surgical specimen. A 73-year-old woman presented with pain on the left side of the mandible within 3 months. On clinical examination, an exposed bone without purulent drainage presented on the left side of the mandible. Before 2 years, she received chemotherapy of zoledronate for multiple myeloma at another hospital. Panoramic imaging showed radiopacities of bone in the left side of the mandibular molar area. Multidetector computed tomography (MDCT) with axial, multiplanar reformation (MPR) and three-dimensional (3D) images showed the sequestrum without periosteal reaction. She was diagnosed as MRONJ, and underwent surgery. Finally, the surgical specimen was diagnosed as multiple myeloma in the sequestrum. This case suggests that the evaluation of the surgical specimen of MRONJ could be essential for detection of primary tumor.