c-myc is not useful as prognostic immunohistochemical marker in cutaneous melanoma

Background: Several studies indicate that immunohistochemical detection of the c-myc oncogene might serve as an additional prognostic marker in malignant melanoma. Objective: To study c-myc expression in paraffin-embedded cutaneous melanoma and to correlate to metastatic potential and onset of metastases. Methods: Cytoplasmic c-myc protein expression was visualized using the APAPP method, and reactivity (percent total tumor cells stained) was assessed in 62 formalin-fixed paraffin-embedded primary cutaneous melanomas (21 not metastasizing, mean Breslow 3.0+/-2.9 mm, 41 metastasizing, mean Breslow 3.1+/-3.0 mm) and 24 metastases of the same patients. Results: There was no significant difference of c-myc reactivity in cutaneous melanoma who did not metastasize (n=21, c-myc reactivity 32.7+/-19.3%, follow-up 10.6+/-1.8 years) and primaries who metastasized (n=4, c-myc reactivity 27.7+/-22.4%, p=0.29). This finding was independent of the thickness of the primary and was found within thin cutaneous melanoma with a Breslow <0.75 mm (range 0.24-0.65 mm, n=20, c-myc reactivity 29.1+/-15.7%, p=0.32) or within thick cutaneous melanoma with a Breslow >1.5 mm (range 1.6-11 mm, n=41, c-myc reactivity 29.6+/-23.8%, p=0.46). No correlation of c-myc expression between thin cutaneous melanoma, thick cutaneous melanoma (p=0.83) or metastasizing pri maries and their metastases (n=24, c-myc reactivity 29.3+/-22%) was found (p=0.64). The time period until development of first metastasis did not correlate with the percentage of cells expressing c-myc in the primary (p=0.56). Conclusion: c-myc expression is independent of metastatic potential and onset of metastases and, therefore, does not serve as a prognostic immunohistochemical marker in primary cutaneous melanoma.