Acute infectious mononucleosis. CD30 (Ki-1) antigen expression and histologic correlations.

Lymph nodes from patients with acute infectious mononucleosis (AIM) typically show marked paracortical expansion and a prominent immunoblastic proliferation that can occur in nodules and sheets, as well as within sinuses. The marked immunoblastic proliferation, coupled with Reed-Sternberg-like cells and a polymorphous inflammatory cell background, may simulate either non-Hodgkin's lymphoma or Hodgkin's disease. A recently described entity, Ki-1-positive lymphoma, or large cell anaplastic lymphoma, shares some clinicopathologic and phenotypic features with AIM and must be considered in the differential diagnosis. The present case describes a 20-year-old male who had signs and symptoms consistent with AIM, which he was later proven serologically to have, but whose cervical lymph node showed features suspicious for large cell anaplastic lymphoma. In addition, the Ki-1 (CD30) antigen was expressed by some of the atypical immunoblasts, further raising this possibility.