Kikuchi Lymphadenitis : Microscopic

Comments:
Microscopic Features of Kikuchi Lymphadenitis: The early proliferative phase of the disease shows expansion of paracortex with mononuclear cells (histiocytes, plasmacytoid dendritic cells) and some karyorrhectic debris. It can closely mimic peripheral T-cell lymphoma which is the main differential diagnosis.

The late necrotic phase shows well-defined areas of fibrinoid necrosis in paracortical areas of the affected lymph nodes. The lymph nodes are often partially involved. The necrotic foci show abundant karyorrhectic and cellular debris, fibrin deposition, and mononuclear cells.

There are no intact neutrophils or eosinophils and only rare plasma cells. Crescentic histiocytes with phagocytized debris are seen. Plasmacytoid dendritic cells, macrophages, and activated T-cells are abundant which can simulate the appearance of a peripheral T-cell lymphoma. Some cases show prominent xanthomatous inflammation.