Sinus histiocytosis with massive lymphadenopathy: the first three cases reported in Thailand.

Three cases of sinus histiocytosis with massive lymphadenopathy are reported in Thai children and is probably a first report in Thailand. They were clinically characterized by bilateral massive cervical lymphadenopathy. Other lymph node groups were also involved but no extranodal manifestations could be detected. Leukocytosis with neutrophilia, hypergammaglobulinemia and polyclonal gammopathy were common features. The characteristic histopathologic findings in the involved lymph nodes included pericapsular fibrosis, markedly dilatation of subcapsular and medullary sinuses which were filled with numerous histiocytes showing active phagocytosis of lymphocytes and lymphoplasmacytoid proliferation in paracortical strands and medullary cord. The disease characteristically has a benign protracted clinical course, and does not respond to either irradiation or chemotherapy. The etiology and pathogenesis of this disorder are unknown. The possible pathologic mechanisms include an abnormal response to a specific infectious process and an immune deficiency status.