Histopathology and bcl-2 immunohistochemistry of in situ follicular lymphoma.

(A-B) Low-power view of H&E-stained (A) and bcl-2–stained (B) sections showing preserved nodal architecture with open sinuses and prominent paracortex. In B, focal germinal centers (GCs) stain strongly positive for bcl-2, 25 × (case no. 4). (C-D) In this case, most follicles have sharply demarcated lymphoid cuffs resembling reactive GCs (C; H&E). A bcl-2 stain (D) reveals a variable number of cells strongly positive for bcl-2, with some GCs containing only rare bcl-2⁺ cells. Note that the intensity of the bcl-2⁺ cells is much higher than that of mantle zone cells and T-lymphocytes, 50 × (case no. 11). (E-F) Stains for bcl-2 show focal GCs strongly positive for bcl-2 protein with some adjacent GCs being completely negative. (immunoperoxidase, hematoxylin counterstain, 50 ×) (case nos. 6, 7). (G-H) At higher power, strongly bcl-2⁺ cells resemble centrocytes, and are seen amid a bcl-2⁻ GC (immunoperoxidase, hematoxylin counterstain, 100 ×, 200 ×) (case no. 11). (I-J) An example of bcl-2–stained sections before (I) and after (J) microdissection of bcl-2⁺ follicles as viewed from the microdissection microscope (immunoperoxidase, no counterstain, 50 ×) (case no. 11).