Kikuchi-Fujimoto disease: a clinicopathologic update.

: Kikuchi-Fujmoto disease (KFD), also known as "histiocytic necrotizing lymphadenitis", is a rare lymphadenitis of unknown origin, but with an excellent prognosis. It is more common in Asia, but isolated cases are also reported in America, Africa and Europe. The disease can have an acute or subacute course, usually develops in 1 to 3 weeks, with spontaneous resolution in 1-4 months. The main clinical sign is cervical lymphadenopathy, especially in the posterior cervical triangle with bulky and painful lymph nodes, usually affecting only one side; rare cases of generalized lymphadenopathy can be seen. This common clinical presentation can also be accompanied by nausea, vomiting, weight loss, weakness, headache and arthralgia. An extranodal extension of the disease, including involvement of skin, eye, and bone marrow localizations, has been rarely described. Most patients have leukopenia or neutropenia with a relative leukocytosis. At an ultrasound exploration of the affected lymph nodes, a hypoechoic aspect can be seen, with an external, thick and irregular hyperechoic ring. As there are no specific tests for KFD, the final diagnosis is histologically-based from lymph node excisional biopsy. Histological examination shows paracortical foci of coagulative necrosis containing karyorrhectic debris, which are surrounded by numerous CD68+/myeloperoxidase (MPO)+ histiocytes, CD68+/CD123+ plasmacytoid dendritic cells, and a minority of small- to large-sized CD8+lymphocytes and immunoblasts. Differential diagnosis mainly includes systemic lupus erithematous (SLE)-related lymphadenopathy and large cell lymphoma. The histological absence of neutrophils, plasmacells, as well as hematoxylin bodies, is a feature which argues against the diagnosis of SLE. In addition, the absence of auto-antibodies and anti-nuclear antibodies is useful in ruling out an autoimmune disorder. Early diagnosis of KFD is crucial to prevent the patients undergo extensive investigations related to suspected malignant lymphomas or other diseases.