MODE OF C-MYC PROTEIN EXPRESSION IN SPITZ NEVI, COMMON MELANOCYTIC NEVI AND MALIGNANT MELANOMAS

The expression of c-myc protein was studied in formalin-fixed, paraffi n-embedded sections of 16 compound Spitz nevi (SNs), 20 ordinary compo und melanocytic nevi (MNs) and 30 malignant melanomas (MMs), using mon oclonal antibody 9E10 and an immunoperoxidase technique. Nine (56%) SN s, 16 (80%) MNs and 23 (77%) MMs showed positive reactions in some of the tumor cells (P = non-significant). The staining reactions were mos tly cytoplasmic, and moderate to strong in intensity. The frequencies of positively stained cells were higher in the MN and SN groups. Most of the lesions with a significant dermal component did not show strati fication of staining with progressive descent into the dermis. Therefo re, the mode of expression of c-myc in routinely processed specimens d oes not differentiate between SNs, MNs and MMs. One possible reason is that the increased expression of the c-myc protein is not sufficient alone to promote proliferation and malignant transformation in these t ypes of tumors.