Differentiation disorders of keratinocytes in seborrheic keratosis (acanthotic type)

Since the differential disorder of keratinocytes in seborrheic keratosis remains to be elucidated, the differentiation of seborrheic keratosis (acanthotic type) was examined immunohistochemically using a lectin and two anti-keratin monoclonal antibodies. A lectin, peanut agglutinin (PNA), and anti-keratin monoclonal antibody, 34 beta B4, recognize the whole epidermis except for the basal layer in the normal epidermis. In seborrheic keratosis (acanthotic type), cells unstained with either PNA or 34 beta B4 were found throughout the entire tumor. In the upper part of the tumor, some cells appeared to undergo keratinization without expressing the differential markers recognized by PNA or 34 beta B4. Another anti-keratin monoclonal antibody, 34 beta E12, stained the tissues in the same way as in the normal epidermis. Thus it was indicated that, in seborrheic keratosis (acanthotic type), although differentiation was partially maintained, some cells might undergo maturation without expressing the differentiation markers recognized by PNA or 34 beta B4.