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 = 41, 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 primaries 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.