Immunopathology of Kikuchi‐Fujimoto Disease: A reappraisal using novel immunohistochemistry combinations

Abstract

AIMS: Kikuchi-Fujimoto disease (KFD) is a self-limited disease characterized by destruction of lymph node parenchyma. Few reports have assessed the immunohistologic features of KFD, and most reports employed limited antibody panels that lacked many of novel immunohistochemistry markers currently available. METHODS AND RESULTS: We reappraised the microanatomic distribution of plasmacytoid dendritic cells (pDCs), follicular helper T-cells and cytotoxic T-cells, B-cells, follicular dendritic cell (FDC) meshworks, and histiocytes in lymph nodes involved by KFD using immunohistochemistry. The study group consisted of 138 KFD patients (89 women; 64.5%) with a median age of 27 years (range, 3-50 years). Cervical lymph nodes were most commonly involved, in 108 (78.3%) patients. The number of pDCs was increased, located predominantly around and within apoptotic areas and the paracortex, and tapering off within xanthomatous areas. pDCs formed sizeable tight clusters most notably around apoptotic/necrotic areas. T-cells consisted mostly of CD8-positive cells with predominant expression of T-cell receptor beta. There was a notable increase in CD8-positive T-cells within lymphoid follicles, and their numbers correlated with alterations in FDC meshworks (p<0.001). Follicular helper T-cells were decreased within distorted FDC meshworks. CD21 highlighted frequent distortion of FDC meshworks, even in lymph node tissue that was distant from apoptotic/necrotic areas. Distorted FDC meshworks spanned all morphologic patterns, and FDC meshwork characteristics (intact; distorted; remnant/nearly absent) correlated with morphologic patterns (p<0.01). CONCLUSIONS: The immunohistologic landscape of KFD is complex and characterized by increased numbers of pDCs that frequently cluster around apoptotic/necrotic foci, increased cytotoxic T-cells, and substantial distortion of FDC meshworks.