Emperipolesis

Emperipolesis is the presence of an intact cell within the cytoplasm of another cell. It is derived from Greek (en is inside, peripoleomai is go round). Emperipolesis is an uncommon biological process, and can be physiological or pathological.

It is related to peripolesis, which is the attachment of one cell to another.

Emperipolesis is unlike phagocytosis, in which the engulfed cell is killed by the lysosomal enzymes of the macrophage. Instead, the engulfed cell remains viable within the other, and can exit at any time without causing structural or functional abnormalities in either cell.

Classification
Emperipolesis has been classified into two categories:
 * 1) Engulfment of hemapoietic cells by megakaryocytes such as in hematolymphoid disorders (Hodgkin's disease, leukemia, acute and chronic myeloid leukemia, non-Hodgkin's lymphoma, myeloproliferative disorders, myelodysplastic syndrome)
 * 2) Engulfment of inflammatory cells by histiocytes, which is a hallmark of Rosai-Dorfman disease

Other associations
It is seen in various conditions including:
 * Autoimmune hepatitis
 * Leukocyte migration from the blood stream to tissues through endothelial cells, in a process also known as transcellular migration and is akin to diapedesis (paracellular migration).