Primary adrenal Epstein–Barr virus‐positive diffuse large B cell lymphoma of the elderly, mimicking pseudocyst

Primary adrenal lymphoma is rare, but clinically important. We report a unique case of adrenal lymphoma which showed extensive cystic change mimicking a pseudocyst. Seventy‐three‐year‐old man visited our hospital for healthcare check‐up, and was found to have a large adrenal cystic mass. He was received adrenalectomy on the impression of an adrenal pseudocyst. On gross examination, the mass was a unilocular cyst with no solid mass formation. Microscopically, the cyst wall had no epithelial lining, but was infiltrated by some atypical large lymphoid tumor cells. The cystic space was filled with coagulative necrotic material with the tumor cell shadow. The most of the tumor cells expressed leukocyte common antigen, CD20, PAX5, Ki‐67, and Epstein‐Barr virus (EBV)‐encoded RNA, which was consistent with EBV‐positive diffuse large B‐cell lymphoma of the elderly. No extra‐adrenal involvement was observed in imaging studies. We concluded that primary adrenal lymphoma should be considered as a rare but important cause of adrenal cysts.