Kikuchi-Fujimoto disease mimicking thyroid metastasis

INTRODUCTION: Kikuchi-Fujimoto lymphadenopathy is a subacute necrotizing lymphadenopathy of unknown origin. It usually affects cervical lymph nodes. Lymph node biopsy is needed for establishing the diagnosis. This disease must be considered as a possible cause of lymphadenopathy of unknown origin, certainly if classical clinical features lead to diagnostic confusion. OBSERVATION: A 41-year-old female presented a thyroid cancer treated by thyroidectomy associated with administration of I131. She also presented a right cervical metastasis treated by surgery. She had a cervical right cervical lymphadenopathy, hypermetabolic on the FDG scan, treated by a modified neck dissection. Microscopy of the surgical specimen showed necroziting lymphadenitis. DISCUSSION: Kikuchi-Fujimoto lymphadenopathy is a subacute necroziting lymphadenopathy of unknown origin, involved more commonly cervical lymph nodes unilaterally. It is more common in Asia, predominantly in young women. This lesion has been reported in patients of virtually any age or gender. No specific biological findings have been described. Lymph node biopsy is needed for establishing the diagnosis. The spontaneous course is usually favorable but one fatal case has been reported.