The histopathology of cutaneous lesions of Kikuchi's disease (necrotizing lymphadenitis) - A report of five cases

Kikuchi's disease (KD) is an idiopathic, self-limited necrotizing lymphaden itis that can clinically and histologically mimic high-grade lymphoma, incl uding Hodgkin's disease, or can be mistaken for the lymphadenitis of system ic lupus erythematosus (SLE). Involvement of extranodal sites is unusual bu t well documented, especially in Asia, where KD is more common than in Nort h America or Europe. The successful distinction of KD from malignant lympho ma and SLE is imperative for the appropriate treatment of affected patients . We describe five patients with cutaneous involvement by KD, all of whom p resented with fever, lymphadenopathy,and an eruption on the skin of the upp er body, which in one case was clinically suspected to be due to SLE and in another, polymorphous light eruption. The patients ranged in age from 10 m onths to 32 years (median, 33 years) and included three females and two mal es. All five patients had negative serologic studies for collagen vascular disease. Each patient had a lymph node biopsy showing the typical necrotizi ng lymphadenitis of KD. Skin biopsies from all five patients shared a speci fic constellation of histologic features: vacuolar interface change with ne crotic keratinocytes, a dense lymphohistiocytic superficial and deep periva scular and interstitial infiltrate, varying amounts of papillary dermal ede ma, and abundant karyorrhectic debris with a conspicuous absence of neutrop hils and a paucity of plasma cells, paralleling the nodal histology in KD, CD68 immunohistochemistry on paraffin-embedded sections showed many histioc ytes and plasmacytoid monocytes in all cases, whereas CD3, CD4, and CD8 sho wed highly variable staining among the cases. There was only rare staining with TIA-I and CD30. We believe that the papular eruption of KD has recogni zable histopathologic features and that a CD68 stain that marks many cells that initially seem to be lymphocytes can be performed to confirm the diagn osis.