Rosai-Dorfman disease (RDD), also known as sinus histiocytosis with massive lymphadenopathy, is a rare, benign, non-Langerhanscell, histiocytic proliferative disease without any known cause.1 Histopathological hallmark of Rosai-Dorfman disease is characteristic histiocytes with abundant pale cytoplasm exhibiting
emperipolesis. Immunohistochemically strongly positive for S100 protein and various markers especially CD68 and CD163.2 Painless cervical lymphadenopathy with or without extra nodal manifestations are among the most common clinical presentations.3 About 40% of Rosai-Dorfman disease cases have extranodal involvement with predominant head and neck region.
The large cells often contain lymphocytes and leukocytes (
emperipolesis) in the cytoplasm, as well as nuclear inclusion.
Inflammatory lymphocytes actively penetrate into the hepatocytes through
emperipolesis. Hepatocellular rosettes are also a histological feature of AIH in which clusters of lymphocytes are surrounded by antigens that may or may not be coated with antibodies (Lohse & Weiler-Normann, 2018).
Emperipolesis, consisting of histiocytes engulfed in well-preserved lymphocytes, was observed in the permanent paraffin-embedded tissues [patient 4, [Figure 5].
Diagnostic pathological changes in AIH were recorded, including interface hepatitis, lymphoplasmacytic infiltrate, hepatocyte resetting, and
emperipolesis. Pathological changes used for the diagnosis of PBC included florid duct lesion, bile duct damage, ductular proliferation, and cholestasis.
Findings again included mixed inflammatory cells, but now also involved abundant foamy histiocytes and eosinophilic histiocytes with
emperipolesis, a phenomenon observed when other inflammatory cells (e.g., neutrophils, plasma cells, and lymphocytes) pass through the cytoplasm of a histiocyte (Figure 1(b)).
Emperipolesis is the engulfment of living and intact hematopoietic cells in the cytoplasm of the host cell [1, 2].
The two classical histological features include scattered histiocytes with
emperipolesis, which represent histiocytic phagocytosis of intact plasma cells, lymphocytes, and cellular debris as well as expression of S100 protein, CD14, CD68, and CD1c and absence of staining for CD1a and MHC-2 (which are both positive for Langerhans-type dendritic cells).
Emperipolesis within the histiocyte cytoplasm is a pathognomonic finding [2-4].
The extranodal lesions and the lymph node lesions were very similar, but the extranodal lesions showed more obvious fibrosis and fewer histiocytes, and
emperipolesis was not common.
Within some of the enlarged histiocytes were intact lymphocytes (
emperipolesis).
While ECD and RDD could be differentiated pathologically (lack of
emperipolesis) or clinically (no massive lymphadenopathy) [14], immunohistochemistry performed on bone marrow (or soft) tissue is essential in distinguishing Langerhans cells from non-Langerhans histiocytes.
