関節リウマチ患者の上顎歯肉に生じた節外性 NK/T 細胞リンパ腫・鼻型の病理像を呈したその他の医原性免疫不全関連リンパ増殖性疾患(OI-LPD)の1例

抄録

This report describes a case of other iatrogenic immunodeficiency-associated lymphoproliferative disorder (OI-LPD) with extranodal NK/T cell lymphoma, nasal type (ENKL), in the maxillary gingiva of a rheumatoid arthritis(RA) patient. OI-LPD in patients with RA are mostly B-cell type. A 75-year-old woman was referred to our hospital because of nasal obstruction and swelling in the maxillary gingiva. A biopsy was performed, and a diagnosis of ENKL was made. Immunohistochemical staining showed that most of the atypical lymphocytes were positive for CD56. In situ hybridization for Epstein-Barr virus-encoded small RNA(EBER) was positive for tumor cells. She had been receiving methotrexate for RA; it was therefore discontinued, and the lesion disappeared. There has been no sign of recurrence after discontinuation of methotrexate. Malignant lymphomas of NK cell origin are rare, and EBV may be involved in the etiology of ENKL. ENKL has a poor prognosis in most cases. There are few reports of OI-LPD that exhibits the pathological features of ENKL, therefore its pathogenesis is not well understood. Hence a long-term close follow-up of this patient will be necessary.