MIB-1 monoclonal antibody to determine proliferative activity of Ki-67 antigen as an adjunct to the histopathologic differential diagnosis of Spitz nevi.

Abstract

The histopathologic differential diagnosis of Spitz nevus (SN) from malignant melanoma (MM) may be difficult. Our purpose was to determine the staining pattern and usefulness of MIB-1 antibody, which recognizes Ki-67 antigen in formalin-fixed, paraffin-embedded tissue, as an adjunct to the histopathologic differential diagnosis of SN. Twenty-five compound SNs, 27 MMs, and 26 compound nondysplastic melanocytic nevi (MNs) were immunostained with the MIB-1 antibody. The mean counts of MIB-1--stained tumor cells of the epidermal and dermal components, both alone and together, were significantly lower in SNs and MNs than in MMs (P <.0001). The dermal counts showed the best discriminating power. In addition, the mean dermal/epidermal count ratios for MIB-1 in SNs and MNs (0.25 and 0.23, respectively) were significantly lower than the corresponding ratio (0.94) in MMs (P <.0001). MIB-1-stained tumor cell counts, especially of the dermal component, and dermal/epidermal MIB-1 count ratios may be helpful as an adjunct to the histopathologic differential diagnosis of SN.