The following are multiple choice questions (with answers) about medical knowledge.   **Question:** A patient presented with intermittent fever, no weight loss, no anorexia, but with a retroperitoneal mass. Peripheral smear findings were normal. Microscopy of the mass is given. What's the diagnosis?   (A) NHL   (B) Castleman disease   (C) Angiolymphoid hyperplasia   (D) Ig G4 disease
['(B) Castleman disease <> answer', 'The following are multiple choice questions (with answers) about medical knowledge. <> instruction', '(A) NHL \n (B) Castleman disease \n (C) Angiolymphoid hyperplasia \n (D) Ig G4 disease <> possible answers', "  A patient presented with intermittent fever, no weight loss, no anorexia, but with a retroperitoneal mass. Peripheral smear findings were normal. Microscopy of the mass is given. What's the diagnosis? <> context@"]