Nodule on the left cheek

Diagnosis: Merkel cell carcinoma

A biopsy performed 2 weeks after the initial visit confirmed the clinical suspicion for Merkel cell carcinoma (MCC).

MCC is a cutaneous neuroendocrine malignancy. Although its name acknowledges similarities between the tumor cells and Merkel cells, it is now considered unlikely that Merkel cells are the actual cells of origin.¹

The growing cohort of ageing baby boomers and the increased number of immunosuppressed individuals in the community suggest that clinicians are now more likely to encounter MCC than in the past.

The majority of MCCs are asymptomatic despite rapid growth and are typically red or pink and occur on UV-exposed areas, as in our patient.² A cyst or acneiform lesion is the single most common diagnosis given at the time of biopsy.²

The incidence of MCC is greatest in people of advanced age and in those who are immunosuppressed. In the United States, the estimated annual incidence rate rose from 0.5 cases per 100,000 people in 2000 to 0.7 cases per 100,000 people in 2013.³ MCC increases exponentially with advancing age, from 0.1 (per 100,000) in those ages 40 to 44 years to 9.8 in those older than 85 years.³ The growing cohort of ageing baby boomers and the increased number of immunosuppressed individuals in the community suggest that clinicians are now more likely to encounter MCC than in the past.

While UV radiation is highly associated with MCC, the major causative factor is considered to be Merkel cell polyomavirus (MCPyV).¹ In fact, MCPyV has been linked to 80% of MCC cases.^1,3 Most people have positive serology for MCPyV in early childhood, but the association between MCC and old age highlights the impact of immunosuppression on MCPyV activity and MCC development.¹

Clinical suspicion is the first step in diagnosing MCC

The mnemonic AEIOU highlights the key clinical features of this aggressive tumor^2,4:

• Asymptomatic
• Expanding rapidly (often grows in less than 3 months)
• Immune suppression (eg, chronic lymphocytic leukemia, solid organ transplant patient)
• Older than 50
• UV exposure on fair skin.

If a lesion is suspected to be MCC, the next step includes biopsy so that a definitive diagnosis can be made. A firm, nontender nodule that lacks fluctuance should raise suspicion for a neoplastic process.

Continue to: The differential is broad, ranging from cysts to melanoma