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?

Explanation

Onion skin appearance of lymph node is characteristic for Castleman disease It is alympho proliferative disorder. It has 2 variants: Unicentric Has 2 variants: 1)Highly vasculara More common , patients are asymptomatic Histology: -Twinning- Presence of two germinal centers -Onion skin pattern-Lymphocytes causes thickening of mantle zone -Lollipop lesions- Sclerosed blood vessel that infiltrate lymph node germinal center Multicentric ?Associated with immune suppression ?Presents as : Hepatomegaly Splenomegaly Night sweats Fever 2)Plasma cell varianta Less common, patients are symptomatic: - Weight loss -Night sweats -Fever Histology: Plasma cells in interfollicular areas causing hyperplasia of germinal center Lymph node architecture is distoed but LN is preserved in unicentric variant