[Systemic sarcoidosis developed after chemoradiotherapy for localized thyroid diffuse large B-cell lymphoma].

Localized thyroid diffuse large B-cell lymphoma stage with stage IE according to the Ann Arbor clinical staging system was diagnosed in a 75-year-old woman. The patient was treated with three courses of chemotherapy followed by radiotherapy. Positron emission tomography/computed tomography (PET-CT) using 2-deoxy-2-[F-18] fluoro-D-glucose (FDG) PET-CT was performed two months after chemotherapy showed increased FDG uptakes in systemic lymph nodes and gluteal muscles. Standardized uptake value in the region of interest ranged from 7.1-26.1. Since it seemed too sudden to be a recurrence, a repeat biopsy was performed from inguinal lymph nodes. Histology revealed that there were no malignant lymphoma cells but noncaseous epithelioid granuloma with multinucleated giant cells. Taken together with the findings of bilateral hilar mediastinal lymphadenopathy and elevated serum angiotensin converting enzyme (ACE) levels (32.4 U/l), sarcoidosis secondary to lymphoma was diagnosed in this patient. Subsequently, both FDG uptake and serum ACE gradually improved without any therapy. The present case strongly suggests the importance of a re-biopsy when the clinical course of recurrence is unusual.