耳下腺原発髄外性形質細胞腫例

抄録

Extramedullary plasmacytomas are rare plasma cell tumors that occur mainly in the head and neck region. We report a case of extramedullary plasmacytoma of the parotid gland. A 32-year-old woman presented to us with the chief complaint of swelling of the right mandibular region. Physical examination and MRI revealed a mass lesion measuring 25×15 mm in the right parotid gland and an enlarged right retropharyngeal node. Fine needle aspiration cytology of the main mass showed the presence of some severely atypical, plasma cell-like cells. For the purpose of definitive diagnosis, a right superficial parotidectomy with preservation of the facial nerve was performed. Histopathological examination of the resected specimen revealed the diagnosis of extramedullary plasmacytoma. Immunohistological studies revealed positive staining of the tumor cells for IgG and the kappa chain of immunoglobulin. There were no abnormalities of the serum immunoglobulin level or serum and urinary protein levels, and no abnormal findings on bone marrow biopsy. Postoperative radiation therapy (intensity modulated radiation therapy: IMRT) was administered at a total dose of 50 Gy to the right parotid gland and retropharyngeal lymph node. According to the literature, extramedullary plasmacytoma often transforms to multiple myeloma after several years or even several decades. Therefore, long-term strict observation after treatment is needed.