Answer: Kikuchi lymphadenopathy

Histology: A single, enlarged lymph node is present, which has a single, irregular focus composed of histiocytes, fibrinoid debris, nuclear debris, and small lymphocytes, in a background of reactive follicular hyperplasia. Neutrophils are conspicuously absent. Some of the histiocytes have engulfed eosinophilic fibrinoid debris, which results in an eccentrically-placed, crescent-shaped nucleus.

Discussion: Kikuchi lymphadenopathy, also known as necrotizing histiocytic lymphadenitis and Kikuchi-Fujimoto lymphoadenopathy, is a benign, usually self-limited condition most commonly seen in young, Asian females and most commonly found in cervical lymph nodes. It can also be seen outside of Asian and in other lymph nodes, and rarely has a disseminated, fulminant course. Very similar in appearance is lupus lymphadenitis, which usually also contains hematoxylin bodies (irregularly-shaped basophilic deposits composed of nuclear debris) and the Azzopardi effect (basophilic deposits within the walls of blood vessels). Also in the differential diagnosis would be other necrotizing lymphadenitides, including cat scratch disease (which should have neutrophils), tuberculosis (which often has caseous necrosis and multinucleated giant cells), and Epstein-Barr virus. Special stains should be performed to rule out the presence of microorganisms.