APOPTOTIC INDEX - DISCRIMINANT FEATURE FOR THE DIFFERENTIATION OF CUTANEOUS DIFFUSE MALIGNANT FOLLICULAR CENTER CELL LYMPHOMAS FROM LYMPHOID HYPERPLASIA

Diffuse subtypes of cutaneous lymphoid hyperplasia (CLH; n = 18) and p rimary malignant follicular center cell lymphoma of the skin (FCCL, n = 11) were diagnosed by conventional histology, immunophenotyping on p araffin sections, and gene rearrangement analysis. We then counted on semithin, Azur A - stained sections of resin - re-embedded biopsy spec imens the relative numbers of apoptotic bodies among all lymphoid cell s (apoptotic index [AI]). The diagnostic value of AI was compared to t hat of mitotic indices (MI) and percentages of various cell types in t he cutaneous infiltrate. Features of cellular infiltrates distinguishi ng to two groups of lesions, in the order of decreasing significance, were percent large lymphoid cells, percent medium-sized lymphoid cells (both higher in FCCL); percent small lymphoid cells, percent epitheli oid/giant cells, and percent histiocytes/macrophages (all three higher in CLH). However, of all parameters tested, AI had the greatest discr iminant value (median in FCCL 1.11%, in CLH 0.14%; p = 8 X 10(-6)). Tw o cases, diagnosed as CLH with all morphologic and immunologic methods used, showed B-cell monoclonality at the DNA level. Linear discrimina nt analysis determined the following order of distinctive power of var iables: 1) AI; 2) MI; 3) percent small lymphoid cells; 4) percent medi um-sized lymphoid cells; 5) percent large lymphoid cells; 6) percent e pithelioid/giant cells; and 7) percent histiocytes/macrophages. The pr esent study thus establishes AI as an important parameter in the diffe rentiation of diffuse CLH from diffuse cutaneous FCCL.