1.37  Epidermotropism and pagetoid cells (see also Clear cell neoplasms 1.22) Epidermotropism refers to migration of malignant cells into the epidermis, usually without significant spongiosis. Exocytosis refers to the migration of cells (usually lymphocytes, neu- trophils, or eosinophils) into the epidermis, usually in asso- ciation with spongiosis (1.132), and usually used for benign conditions. Pagetoid cells are cells in the epidermis, often pale or atypical, resembling Paget’s disease. Pagetoid cells may or may not arrive in the epidermis by means of epidermotro- pism. Pagetoid melanocytes (Chapter 20) are best known in melanoma, but are also seen in benign melanocytic neoplasms such as Spitz nevus, pigmented spindle cell nevus, congenital nevus in neonates, recurrent nevus, and acral nevus. Care must be taken not to mistake melanocytes in tangentially sec- tioned epidermis for pagetoid cells, 160 nor to mistake common artifactual vacuoles around keratinocytes for pagetoid cells (1.144).