On the other hand, pathological characteristics exclusive to RDD were also confirmed in our study, including S-100( +), CD38( +), CD68( +) and emperipolesis in histopathological analysis in all samples from the RDD mimic IgG4-RD group but not in the IgG4-RD group. Here, CD38 is linked to sinus histiocytosis with massive lymphadenopathy.