Enhanced Verifiable CPD from the
University of Birmingham

Dentaljuce Shorts: 500 words, 10 MCQs, on general medicine and surgery.

Merkel-cell carcinoma

Merkel-cell carcinoma (MCC) is a rare and aggressive skin cancer, affecting approximately three people per million. Also known as cutaneous APUDoma, primary neuroendocrine carcinoma of the skin, primary small cell carcinoma of the skin, and trabecular carcinoma of the skin, MCC development involves factors such as Merkel cell polyomavirus (MCV), weakened immune systems, and ultraviolet radiation exposure. Commonly arising on the head, neck, extremities, perianal region, and eyelid, MCC is more prevalent in individuals over sixty years old, Caucasians, and males, and is rare in children.

Small spot on the left arm is Merkel cell cancer.
Small spot on the left arm is Merkel cell cancer.

Signs and Symptoms

Merkel cell carcinoma. Gross pathology specimen.
Merkel cell carcinoma. Gross pathology specimen.

MCC usually presents as a firm nodule or mass, flesh-coloured, red, or blue, varying in size from 0.5 cm to over 5 cm and potentially enlarging rapidly. Tumours can be painless, tender or itchy, and may present as papules or plaques. MCC frequently occurs in sun-exposed areas like the head, neck, and extremities. The acronym AEIOU (Asymptomatic, Expanding rapidly, Immune suppression, Older than 50 years, and Ultraviolet-exposed site on a person with fair skin) summarises key attributes of MCC. Ninety percent of MCC cases have three or more of these features. MCC is often mistaken for other cancers or benign cysts and tends to invade locally, infiltrating underlying subcutaneous fat, fascia, and muscle, and metastasizing early, most often to regional lymph nodes, liver, lung, brain, and bone.

Pathophysiology

Micrograph of a Merkel cell carcinoma. H&E stain.
Micrograph of a Merkel cell carcinoma. H&E stain.
Merkel cell carcinoma (arrow) infiltrating skin tissue, stained brown for Merkel cell polyomavirus large T protein
Merkel cell carcinoma (arrow) infiltrating skin tissue, stained brown for Merkel cell polyomavirus large T protein

While initially named for its histologic similarity to Merkel cells, the precise cellular origin of MCC is debated. Merkel cells, involved in pressure sensation in the epidermis, are unlikely progenitors. Evidence suggests MCC may originate from precursor cells such as fibroblasts or epithelial cells in hair follicles. Factors involved in MCC pathogenesis include MCV infection, UV radiation, and immune suppression. MCV, a small double-stranded DNA virus, is integrated into the host genome in about 80% of MCC tumours, though most MCV infections remain asymptomatic. UV radiation is implicated in 20% of MCC cases, which tend to have high mutational burdens with UV damage signatures. Immunosuppression also increases MCC incidence and impacts prognosis.

Diagnosis

Photomicrographs of a typical Merkel cell carcinoma at various magnifications.
Photomicrographs of a typical Merkel cell carcinoma at various magnifications.

Diagnosis begins with clinical examination and requires biopsy tissue for histopathologic features. MCC shows basaloid tumour nests with neuroendocrine features. Immunohistochemistry (IHC) is often needed to differentiate MCC from similar tumours. Markers like synaptophysin, chromogranin A, PAX5, and cytokeratin 20 help in diagnosis. Sentinel lymph node biopsy and imaging (e.g., PET or CT scan) are recommended for staging and determining treatment.

Prevention

Preventing excessive UV exposure is very important in reducing MCC risk. Recommendations include limiting sun exposure between 10 am and 4 pm, seeking shade, wearing sun-protective clothing, using sunscreen, and avoiding tanning beds.

Treatment

Surgery

Surgical resection, often a wide excision or Mohs surgery, is typically performed prior to other treatments. Sentinel lymph node biopsy is often conducted simultaneously.

Radiation

Radiation therapy is a primary treatment modality, sometimes used alone, achieving outcomes comparable to surgery followed by radiation.

Chemotherapy

Traditional chemotherapy is reserved for late-stage cases due to significant adverse effects and limited long-term benefits. No FDA-approved standard chemotherapy regimens exist.

Drug Therapy

Immunotherapies targeting the PD1-PDL1 checkpoint pathway, such as avelumab and pembrolizumab, have shown benefits in advanced or chemotherapy-resistant MCC, with clinical response rates between 50 and 65%.

Prognosis

Prognosis varies significantly by stage at diagnosis, with five-year survival rates ranging from 80% for stage IA to 20% for stage IV. Factors influencing prognosis include MCV viral status, histological features, and immune status. The antibody titer to MCV oncoprotein serves as a treatment response biomarker in some patients.

Epidemiology

MCC is most common in Caucasians aged 60-80, with a higher incidence in males. It is a rare skin cancer, with increasing incidence, particularly in regions with high sun exposure, such as Australia. Other primary cancers and immunosuppression increase MCC risk.


Self-assessment MCQs (single best answer)

What is the estimated incidence rate of Merkel-cell carcinoma (MCC)?



Which virus is associated with the development of MCC?



What is the most common age group affected by MCC?



Which of the following is NOT a common site for MCC occurrence?



What does the acronym AEIOU stand for in the context of MCC?



What is the primary method for diagnosing MCC?



Which immunohistochemical marker is NOT typically used in diagnosing MCC?



Which treatment modality is often reserved for late-stage MCC due to its adverse effects?



What is the approximate five-year survival rate for stage IV MCC?



Which factor is NOT associated with an increased risk of MCC?



Dentaljuce

Dentaljuce provides Enhanced Continuing Professional Development (CPD) with GDC-approved Certificates for dental professionals worldwide.

Founded in 2009 by the award-winning Masters team from the School of Dentistry at the University of Birmingham, Dentaljuce has established itself as the leading platform for online CPD.

With over 100 high-quality online courses available for a single annual membership fee, Dentaljuce offers comprehensive e-learning designed for busy dental professionals.

The courses cover a complete range of topics, from clinical skills to patient communication, and are suitable for dentists, nurses, hygienists, therapists, students, and practice managers.

Dentaljuce features Dr. Aiden, a dentally trained AI-powered personal tutor available 24/7 to assist with queries and provide guidance through complex topics, enhancing the learning experience.

Check out our range of courses, or sign up now!

Membership Options

Dentaljuce offers a range of membership options…

Regular Membership

With enhanced CPD Certificates. Dentaljuce is brought to you by the award winning Masters team from the School of Dentistry, University of Birmingham, UK. All have won awards for web based learning and teaching and are recognised as leaders and innovators in this field, as well as being highly experienced clinical teachers. Full access to over 100 courses, no extras to pay.

Buy Now

£89.00 per year

Student Membership

No Certificates. With universities cutting down on traditional lectures, many students are currently having to rely more on online resources. If you don't need CPD Certificates, we are offering an amazing discount on your Dentaljuce personal membership fee. Special student price just £29 for 12 months individual membership.

Buy Now

£29.00 per year

It has to be the best value CPD around, and probably the most useful. Many thanks.
WK

© Dentaljuce 2024 | Terms & Conditions | Privacy Policy

Recording CPD time: recorded.