Answer: Toxoplasma gondii lymphadenitis. This is a rare case in that cysts are not typically seen in the affected lymph nodes. Instead, pathologists rely on the classic pathologic features (e.g. lymph node architecture and pattern of inflammatory cells) to suggest the diagnosis, which should then be correlated with clinical features and serologic tests.
Findings that may mimic the cysts of T. gondii include T. cruzi pseudocysts and macrophages with Leishmania spp. amastigotes or Histoplasma capsulatum yeasts.