[Histiocytic necrotizing lymphadenitis / Kikuchi-Fujimoto disease (HNL/K-F) and its differential diagnosis: analysis of 19 patients].

Histiocytic necrotizing lymphadenitis / Kikuchi-Fujimoto disease (HNL/K-F) is being recognized with an increasing frequency not only in the East Asia but also on the American continents and in the Europe. Still the diagnostics of HNL/K-F is not easy and difficulties with its proper classification persist. In a group of 19 patients diagnosed primarily or as consults at our department there were 12 woman and 7 men. An average age at diagnosis was 28 years, median 25 years. Cervical lymph nodes were involved in 18 patients. Bilateral lymphadenopathy was present in one patient, the remaining 17 were unilateral. Inguinal lymph node was affected in one patient. In one other patient there were enlarged retroperitoneal lymph nodes simultaneously with a cervical lymphadenopathy. The size of the lymph nodes varied between 5 mm to 32 mm. The subclassification showed the necrotizing type in 14 patients, in one there was a predominant xanthomatous tissue reaction around the necrotic areas (xanthomatous type), and in 4 patients the disease was recognized as the proliferative type without necrosis (in two with a variously intense apoptosis of the proliferating lymphocytes). Of 10 consult cases the tumor was primarily evaluated as B cell lymphoma not otherwise specified (1x), peripheral T cell lymphoma (1x), classical Hodgkin lymphoma of mixed cellularity (1x); two patients were submitted with a differential diagnosis between peripheral T cell lymphoma and HNL/K-F; in one diagnosis of probable EBV lymphadenitis and in one diagnosis HNL/K-F was made. There were no data submitted in the remaining three cases. The authors stress diagnostic features which should lead to the diagnosis of the disease and should prevent unnecessary oncological staging investigations and potential chemotherapy for a lymphoma. Among diagnostic features of HNL/K-F identification of the proliferating cells - CD8 activated lymphocytes with apoptotic decay prevail, there are frequent plasmacytoid monocytes and a striking reaction of macrophages which are CD68/myeloperoxidase positive. There are virtually no neutrophil granulocytes and there is a miminal participation of plasma cells. In case of necrotizing and xanthomatous type infectious causes are to be ruled out as well. In case we still need to distinguish HNL/K-F from a lymphoma PCR analysis of a rearrangement of the immunoreceptor gene in T cell population should be investigated.