Cutaneous Follicle Center Lymphoma : Differential

Comments:
Primary cutaneous follicle center lymphoma (PCFCL) vs Primary Cutaneous Diffuse Large B-cell Lymphoma, Leg Type (PCDLBCL, LT) - Differential Diagnosis (continued).

Features favoring PCDLBCL, LT:

• rapidly growing cutaneous tumors on lower legs usually in older women
• sheets of centroblasts or immunoblasts
• T-cells absent or in scant numbers in perivascular location
• CD20+, CD79a+, PAX5+, IgM+, IgD+/-, light chain restriction
• BCL6+ (68% of cases), BCL2+, CD10- (pos in <10%)
• IRF4/MUM1+, FOXP1+; positive MYC expression
• absence of follicular dendritic cell meshwork with CD21/CD35
• gene expression profile of activated B-cell type DLBCL
• translocations involving BCL6 (30%), MYC (30%), IGH (50%)
• del 6q (BLIMP1; 60%); del 9p21.3 (CDKN2A; 67%)
• NF-κB pathway mutations - MYD88 (60%), CD79B (20%), CARD11 (10%), TNFAIP3 (40%)
.