Fine Needle Aspiration Cytology of Kikuchi’s Lymphadenitis: with Emphasis on Differential Diagnosis with Tuberculosis

Kikuchi’s lymphadenitis (KL), also called as histiocytic necrotizing lymphadenitis, is a reactive condition of a lymph node which has a distinct clinical manifestation but unknown etiology. In most of the cases, it presents as a cervical lymphadenopathy mainly in young adults, especially women. It undergoes a self-limiting course within a few weeks to several months. However, unnecessary excisional biopsy is still being performed in patients due to high occurrence of false negative or false positive rates of cytologic diagnosis based on fine needle aspiration cytology (FNAC). Although KL has been known to have characteristic cytological features such as, karyorrhectic debris, crescentic histiocytes, extracellular and intracellular apoptotic bodies, plasmacytoid lymphocytes and rare neutrophils, pathologists sometimes face difficulties in making a cytologic diagnosis because KL shares several cytologic features with other reactive and neoplastic conditions such as, tuberculosis, lupus lymphadenitis, malignant lymphoma, and nonspecific reactive lymphadenitis, etc. In particular, KL shares many cytological and histological features with tuberculosis with extensive necrosis, and sometimes it is difficult to differentiate them cytologically. There have been several reports about FNAC of KL, however, the collective studies using cases confirmed by histology have been not many. The objective of this study was to assess the diagnostic pitfalls of KL with FNAC, particularly with emphasis on differential diagnosis with tuberculosis.