Tips for Diagnosing and Managing MCC

When should dermatologists suspect Merkel cell carcinoma (MCC) and what are the latest best practices for diagnosis and management?

Presenters Song Park, MD, IFAAD, an acting instructor in the division of dermatology at the University of Washington School of Medicine and a physician at the Seattle Cancer Care Alliance (SCCA), Manisha Thakuria, MD, co-director of the Merkel Cell Carcinoma Center of Excellence at the Dana-Farber Brigham Cancer Center Merkel Cell Carcinoma Center of Excellence and assistant professor of dermatology at Harvard Medical School, both in Boston, Massachusetts and Lisa Zaba, MD, PhD, clinical associate professor of dermatology, and director of the Merkel Cell Carcinoma Multi-Disciplinary Clinic at Stanford Health Care in San Jose, California dove into the subject in a presentation¹ at the 2022 American Academy of Dermatology (AAD)’s Annual meeting.

The physicians said that a “high index of suspicion” is necessary as many MCCs are misdiagnosed at biopsy, with 56% presumed benign and 32% presumed a cyst or acneiform lesion.² This level of suspicion is key as MCCs have a variable appearance. In color, they can be pink, red, flesh-colored, or violaceous and can present in many ways like exophytic, dome-shaped, or subcutaneous.

The 2 hallmarks to look for are the lesions being firm, not tender, and growing rapidly. As for patient risk factors, the presenters noted that patients diagnosed with MCCs are more likely to be elderly (median age of 75), white, and immunocompromised.

When dermatologists suspect a MCC, the presenters noted 3 pearls for diagnosis. “Measure and record the clinical diameter [critical for tumor staging], inspect and palpate the surrounding skin for in-transit metastases and, for a subcutaneous nodule, hub your punch biopsy because tumors are often centered in the deep dermis or fat,” said Thakuria.

Next, they outlined what is needed for a staging workup. Dermatologists need to perform a full skin and lymph node examination to identify in transit metastases and regional lymphadenopathy (present in 25% of patients). They also need to do a “scalp-to-toes” positron emission tomography–computed tomography (PET/CT) or CT scan and a sentinel lymph node biopsy to identify microscopic lymph node metastases that do not show up on imaging. All clinically node negative MCCs still merit consideration of sentinel lymph node biopsy, which could cause upstaging in 25-32% of patients.³

According to the presenters, dermatologists should follow a checklist of steps for a patient with MCC, which includes:

• An appointment made as soon as it can with the dermatologists for the full-body scan referred to above;
• Referrals to, ideally, a tertiary care center for multidisciplinary management (the presenters noted that experience is especially important in managing MCC) including radiation and surgical oncology. Also, dermatologist should follow up to ensure prompt consultations—ideally within 1 to 2 weeks—for the patient;
• Order baseline image or make sure the referred specialists will do so;
• Draw oncoprotein antibody (AMERK) testing as soon as possible to establish an accurate baseline and help with long-term monitoring.

Finally, the presenters described the surveillance plan for patients with MCC. Full skin and lymph node examinations should be performed every 3 to 6 months for the first 3 years, then 6 to 12 months thereafter. Imaging should be routine for high-risk patients and symptom-directed for low-risk patients. AMERK testing should be done every 2 to 3 months for the first 2 to 3 years for patients who were seropositive at diagnosis, as a rising titer can be an early indication of recurrence.

Disclosures

Park has served as an advisory board member, speaker, and/or has received grants/research funding from EMD Serono. Thakuria and Zaba report no relevant disclosures.

References

1. Park S, Thakuria M and Zaba L. Merkel cell carcinoma: updates in practice management. Presented at: American Academy of Dermatology Association 2022 Annual Meeting; March 25 to 29, 2022, Boston, Massachusetts.

2. Heath M, Jaimes N, Lemos B, et al. Clinical characteristics of Merkel cell carcinoma at diagnosis in 195 patients: the AEIOU features. J Am Acad Dermatol. 2008;58(3):375-381. doi:10.1016/j.jaad.2007.11.020

3. Tarantola TI, Vallow LA, Halyard MY, et al. Unknown primary Merkel cell carcinoma: 23 new cases and a review. J Am Acad Dermatol. 2013;68(3):433-440. doi:10.1016/j.jaad.2012.07.035