Demonstration of gap junctions by lanthanum in the vitamin A acid-treated skin tumor, keratoacanthoma.

In normal rabbit epidermis or in the untreated skin tumor, keratoacanthoma the usual cell junction is the desmosome. Gap junctions are very sparse. The extracellular tracer material, lanthanum nitrate was used to confirm the definite identification and increase of gap junctions in the vitamin A acid-treated keratoacanthoma. Without the use of lanthanum, the gap may not be always apparent in conventional thin sections and can be confused with the zonula occludens.