Clinical, biological, and pathological features of GZL and related entities. GZL should be distinguished from EBV-positive DLBCL, which may show similar morphological features. The current study provides new data that more clearly separate GZL arising in the thymic niche from those arising in extramediastinal sites. The clinical case illustrated arose in an inguinal lymph node in a 54-year-old woman. It has features of GZL, being positive for CD20, CD30, and CD15 (hematoxylin & eosin and immunohistochemical staining for the indicated markers). The tumor was positive for BCL2 rearrangement. Notably, a focus of in situ follicular neoplasia was identified in “reactive follicles” adjacent to the tumor mass (inset). The patient relapsed 2 years later with follicular lymphoma, shown to be clonally related to the nonmediastinal GZL.