Incidence of Merkel Cell carcinoma in the Republic of Ireland (1994-2019)
Written by Claire Doyle, Dermatology Department, Tallaght Hospital
Merkel Cell Carcinoma (MCC) is a rare aggressive neuroendocrine cutaneous malignancy most commonly observed in those over 65 years of age.1
MCC is twice as common in males compared to females and is 25 times more common in those with fair skin compared to those with darker skin.2 Solid organ transplant recipients have a 24-fold increased risk of developing MCC.3.
Merkel Cell human polyomavirus (MCPyV) which is found on healthy skin has been found to contribute to 80% of MCC via integration of the virus into the host cell genome. The other 20% of cases are UV radiation induced and do not demonstrate viral genomic integration. There has been an 95% increase in incidence in MCC in the United States from 2000 to 2013 with further increases predicted.4
The aim of this study was to investigate the trends of incidence of MCC in the Republic of Ireland. The National Cancer Registry of Ireland (NCRI) collects data on all cancers diagnosed in Ireland, using the International Classification of Diseases for Oncology (version 2 1994-2004, version 3 2005-2011, version 3.1 2012-2019) to code the topography and morphology of registered tumours.
The data regarding MCC diagnosis was from histopathology reports. NCRI provided data on the number of MCC diagnoses from 1994-2019 (morphology code M-8247/3). Age-standardised rates were calculated using the 2013 European standard population.
There were 447 histologically confirmed MCC diagnosed between 1994 and 2019. 49.2% (220/447) were in males. Median age was 80 years (range 15-19 years to 95+ years). Median for males was 78 years, median for females was 82 years.
On average there were 7 cases of MCC diagnosed per year between 1994 and 1998 compared to 27 cases of MCC per year diagnosed between 2015-2019 almost a quadrupling of case numbers over the course of the time period.
Due to relatively small absolute numbers of MCC diagnosed we report the ASR in five-year time periods. The results are detailed below in table one and showing that the ASR of MCC has significantly increased in male patients from 1994 to 2019.
In contrast, the ASR of MCC has not significantly increased in females over the same time period despite an increase in absolute numbers. Previous literature has indicated that MCC is twice as common in males and in females2. Our cohort differed to this in that there was a slight female predominance in patients diagnosed with MCC.
While the absolute numbers of MCC diagnosed in Ireland has increased in both male and female patients, the age adjusted incidence rate is increasing in males but there has not been a significant change in females.
Other Northern European groups have also demonstrated both a female predominance in absolute numbers of MCC and an increase in incidence of MCC in males that was not observed in females.5 This contrasts with increases in both genders observed in the United States. Further research is needed to explain this gender discrepancy.
This article adds to the data on MCC which is important for service provision and planning for dermatology, radiology, histopathology, radiation oncology and plastic surgery.
References
1. Xue, Y., & Thakuria, M. (2019). Merkel Cell Carcinoma Review. Hematology/Oncology Clinics of North America, 33(1), 39–52. doi:10.1016/j.hoc.2018.08.002
2. Agelli M, Clegg LX. Epidemiology of primary Merkel cell carcinoma in the United States. J Am Acad Dermatol 2003. https://doi. org/10.1016/S0190-9622(03) 02108-X.
3. Clarke CA, Robbins HA, Tatalovich Z, et al. Risk of Merkel cell carcinoma after solid organ transplantation. J Natl Cancer Inst 2015. https://doi.org/10.1093/ jnci/ dju382.
4. Paulson KG, Park SY, Vandeven NA et al. Merkel cell carcinoma: current US incidence and projected increases based on changing demographics. J Am Acad Dermatol 2018; 78:457–63
5. Hussain SK, Sundquist J, Hemminki K. Incidence trends of squamous cell and rare skin cancers in the Swedish national cancer registry point to calendar year and age-dependent increases. J Invest Dermatol. 2010;130:1323–8.
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