Tumor Antigen Expression in Compound Dysplastic Nevi and Superficial Spreading Melanoma Defined by a Panel of Nevomelanoma Monoclonal Antibodies

Studies of antigen expression in dysplastic nevi have been limited to some extent by difficulties in obtaining frozen nevi with which to react monoclonal antibodies. Accordingly, we obtained a panel of antibodies that binds to antigens preserved in paraffin-embedded tissue. This panel of monoclonal antibodies, raised against nevomelanoma antigens, was used on 26 dysplastic compound nevi and additionally on 14 invasive superficial spreading melanomas. Among the dysplastic nevi, two basic dermal staining patterns emerged. One pattern designated "Type 1" shows a histologically well-developed dermal component that tends to be antigenically well stratified, with the cells in the upper dermis expressing the most antigen, and gradual loss of antigenicity in the lower dermis as maturation of nevic cells occurs. A second ("Type 2") pattern was seen in which nevic cells tended to remain in the upper dermis, with less downgrowth, and to express antigen in a diffuse or patchy, but nonstratified distribution. Some differential distribution of the antigens was noted, with antibodies 404-101, HMB-45, and ME 109 binding to the activated junctional zone, but showing lower binding affinity within the dermis. ME 491, NKI-C3, and 506 bind to antigens abundant in the junctional zone as well as the dermis. The antibody ME 67-6 binds to both junction and dermis, but is more useful for delineation of antigenic stratification and presence of abnormal "clones."