Immunohistochemical studies showed that the histiocytes expressed CD163 and S100, while ERG and D2-40 highlighted their intralymphatic confinement, ultimately leading to the diagnosis of intralymphatic RDD.
Rosai-Dorfman disease (RDD) is an enigmatic histiocytic disorder classically diagnosed by a distinctive combination of pathological features: emperipolesis, or migration of intact haematological cells through the voluminous cytoplasm of lesional histiocytes, and expression of S100 by these histiocytes.
Rosai-Dorfman disease (RDD) is an uncommon disorder, characterized by an atypical expansion of histiocytes which classically shows emperipolesis and immunoreactivity with S-100 protein.
Herein, we describe a patient carrying a high titer of autoantibodies to interferon (IFN)-γ with disseminated Mycobacterium kansasii infection presenting with emperipolesis and Rosai-Dorfman disease (RDD)-like histopathological features characterized by remarkable, large, pale-staining "RD cells", which were CD68 and S100 positive and CD1a negative.
Histopathologic evaluation of the specimens revealed inflammatory lesions containing atypical S100-immunoreactive histiocytes diagnostic of Rosai-Dorfman disease, but not an increase in the IgG4-positive plasma cells.