Merkel cell carcinoma: changing incidence trends.

BACKGROUND: The objective of this study was to define the incidence trends of Merkel cell carcinoma (MCC), a rare and aggressive cutaneous malignancy.

MATERIALS AND METHODS: All cases of MCC of the skin between 1986 and 2001 were identified using the surveillance, epidemiology, and end results (SEER) program. Overall age-adjusted, gender-specific, age-specific, stage-specific, and regional incidence rates were calculated. All rates are per 100,000 and age-adjusted to the 2000 US standard population. Estimated annual percent change (EAPC) was calculated using a linear least squares model.

RESULTS: A total of 1,124 cases of MCC were identified in the SEER registries. The rate of MCC increased from 0.15 cases per 100,000 in 1986 to 0.44 cases per 100,000 in 2001. The EAPC for the time period was 8.08%. This was statistically significant (95% CI: 6.29, 9.90, P-value < 0.05). Age-specific incidence (5-year age groups) were highest in the elderly, 4.28 per 100,000 in the 85+ age group.

CONCLUSIONS: MCC incidence rates have increased threefold over the 1986-2001 period. Rates are highest in the elderly population. Further etiologic studies and identification of high-risk populations are warranted.