THE PATTERN OF HMB-45 ANTIBODY STAINING IN COMPOUND SPITZ NEVI

We studied the staining pattern of HMB-45 antibody in 29 compound Spit z nevi (SNs) of the epithelioid cell variety, 17 of which showed exten sion of nevus cells into the reticular dermis (i.e., ''deep''); 20 ord inary compound nevi (CNs), all with a deep dermal component; and 22 pr imary cutaneous invasive malignant melanomas (MMs) (excluding the desm oplastic and spindle cell types), 12 of which extended into Clark leve l IV or V. Of the 29 SNs, eight (28%) stained negatively; five (17%), including two deep SNs, stained in the epidermal component only; and 1 6 (55%), including 10 deep SNs, stained in both the epidermal and derm al components. Of the latter 10 deep SNs, eight stained in the upper d ermis only, and in the remaining two lesions, a smaller number of posi tively stained nevus cells were detectable in the lower dermis as well ; these two SNs were not atypical histologically. Of the 20 CNs, four (20%) stained negatively, two (10%) stained in the epidermal component only, and 14 (70%) stained in the epidermal component and the upper d ermis only. Of the 22 MMs. one stained negatively, and 21 (95%) staine d positively in both the epidermal and dermal components. The pattern was variable in frequency of both staining and distribution, but showe d no stratification. We conclude that the majority of our positively s tained deep compound SNs showed a stratified pattern of HMB-45 stainin g, similar to ordinary CNs and different from MMs, and that this patte rn might be used as an adjunct in the histopathologic differential dia gnosis of compound SN and MM, in the proper clinicopathological contex t.