Epidermotropism/Exocytosis

Epidermotropism and Exocytosis

Exocytosis refers to the migration of inflammatory cells into the epidermis whereas Epidermotropism refers to the migration of malignant cells into the epidermis.

Exocytosis occurs in inflammatory diseases such as Eczema and Psoriasis and Pityriasis lichenoides (acute and chronic) but also in Erythema multiforme and graft versus host disease with lymphocytic exocytosis. Sweet's syndrome is another condition showing exocytosis  but here the cells are neutrophils.

Epidermotropism- We particularly think of epidermotropism and T cell lymphoma with atypical lymphocytes being found in the epidermis sometimes in nests as in Pautrier microabscesses. Histiocytoses can also be seen in the epidermis and the various conditions showing Pagetoid spread may sometimes also be exhibiting epidermotropism when the cell of oprigin is not a normal inhabitant of the epidermis.