Cutaneous manifestation of Kikuchi's histiocytic necrotizing lymphadenitis.

A young man who presented with cervical Kikuchi's histiocytic necrotizing lymphadenitis later developed a cutaneous plaque lesion. Histologic study of the cutaneous lesion revealed dermal patchy infiltrates composed of large lymphoreticular cells and scattered cells resembling Hodgkin or Reed-Sternberg cells. This condition was initially mistaken for a large-cell lymphoma. But it was later discovered that the dermal cellular infiltrates were similar to that of the involved lymph node. Many of the large cells in the infiltrates were found to be histiocytes. Immunohistochemical study revealed that the cells resembling Hodgkin or Reed-Sternberg cells were activated fibroblasts. The presence of foamy histiocytes and the absence of neutrophils in the skin lesions were also similar to the involved lymph node. Cutaneous Kikuchi's disease may be mistaken for cutaneous lymphoma. Cutaneous involvement by Kikuchi's disease may also denote a worse clinical course.