The histology and immunohistochemistry of a lymph node. (a) Gross examination of the lymph node architecture shows prominent vessels, suggesting the formation of the arborizing high endothelial venules. (b) The expanded CD21-positive follicular dendritic cell meshworks. (c) Hematoxylin and eosin stain showing polymorphous background infiltrate composed of medium sized atypical lymphocytes and enlarged pleomorphic cells with unilobated nuclei and prominent nucleoli, resembling RS-like B-cells. (d) The RS-like B-cells have less prominent CD20 expression in comparison to the B-lymphocytes present in the polymorphous infiltrate. (e) The RS-like B-cells are CD30-positive with characteristic paranuclear dot-like staining. (f) The lymphoid population consists of the CD2-positive atypical T-lymphocytes that often form rosettes around RS-like B-cells. (g) and (h) Atypical T-lymphocytes are CD10- and BCL6-positive.