Julia Grabowski¹, Sidney L Saltzstein^1,2,3,4, Georgia Robins Sadler^3,4, Zunera Tahir⁴ and Sarah Blair^3,4

¹Department of Family and Preventive Medicine, University of California at San Diego School of Medicine, La Jolla, CA. ²Department of Pathology, University of California at San Diego School of Medicine, La Jolla, CA. ³Department of Surgery, University of California at San Diego School of Medicine, La Jolla, CA. ⁴Rebecca and John Moores UCSD Cancer Center, University of California at San Diego School of Medicine, La Jolla, CA.

Abstract

Introduction: Melanoma and Merkel cell carcinoma (MCC) are both aggressive skin malignancies associated with immunosuppression and possible UV exposure. Both tumors get similar surgical treatment; however, MCC is a relatively rare tumor in which less is known about prognosis and clinical behavior.

Methods: The California Cancer Registry (CCR), a population-based registry, was reviewed from the years 1988–2003. Merkel cell carcinoma and melanoma were compared with relation to gender, age, ethnicity, disease stage, site, and survival.

Results: A total of 113,187 cases of melanoma and 1,878 cases of MCC were identified in the CCR. Though both cancers are more common in men than in women, MCC had a higher incidence in men than melanoma (63% vs 57% p < 0.005). MCC occurs in the more elderly, with 73.6% of cases occurring in people over 70 years. In contrast, 69% of melanoma cases occurred in people younger than 70 years (p < 0.005). MCC shows a predilection for the head and neck compared to melanoma (47% vs 25.8%) Additionally, melanoma occurs more frequently on the trunk than MCC (30% vs 8.7%). Finally, the 10-year cumulative survival is lower for MCC than for melanoma (17.7% vs 61.3%, p < 0.005).

Conclusion: Many clinicians assume MCC and melanoma behave similarly. However, MCC occurs in an older population, more frequently on the head and neck, in a higher percentage of men. Additionally, MCC has a higher rate of regional metastasis and thus may have more of a benefit from regional staging procedures. Overall, MCC has a worse prognosis.