Merkel Cell Carcinoma
Rare neuroendocrine cancer
Rapidly growing firm, intradermal nodule

Sun exposed areas
Older age (median 43y; M>F 3:1

Now known caused by the polyomavirus
- more common in immunosuppression

CT or PET should always be used to evaluate regional nodes and mets
- 15% involvement
- and 2% metastatic at diagnosis
- liver, bone, brain and lung

Treatment is WLE
- 1.5-2cm margins and down to fascia
- or Mohs to obtain negative margins

Margins and size are prognostic

Can do SNL or regional dissection and adjuvant radioRx to primary and lymph node sites
- improves local control and survival in the poor-prognosis group.

Cisplatin and Etoposide Chemo for regional or distant mets

Failure commonly local (30%) or regional nodes (50%) and 90% of recurrences are in first 2 y
Overall 5-y survival is 70% if node negative, 50% if nodes involved, 20% if mets

Merkel cell carcinoma

What is a Merkel cell

• Non-neuronal cell in the basal layer of the epidermis

• Associated with free sensory nerve endings in the skin when they form a Merkel cell-neurite complex

• Originally suggested to have neural crest origin, it is now clear that they have an epidermal origin

• They are APUD cells. (Amine Precursor Uptake Decarboxylase – endocrine cells)

• They are essential for the specialized coding by which afferent nerve fibers resolve fine spatial detail.

What is the characteristic appearance of a Merkel call cancer

Trabeculae or sheets

Uniform cells

— Round or dendritic appearance

— Multiple secretory granules

mitotic rate

— cutaneous lymphoma

— 2° oat cell carcinoma – indistinguishable from small cell carcinoma of lung histologically for which reason the initial work-up should include a chest X-ray.

Stain with

— K20

— neuron specific enolase (neuroendocrine marker)

What are the clinical features of Merkel cell cancer

• Caucasian age 60-80, 2 - 4.5/1000,000 population (100x rarer than melanoma)

• Male>Female: 2:1

• Risk: Merkel Cell Polyomavirus infection, sun-exposed skin, immunosuppression

• Rapidly growing red or blue-red nodule

            most frequently in the head and neck region

            rarely trunk, lower legs or arms

• The skin lesions do not ulcerate

Aggressive with high rate of local recurrence (45%)

Metastasises rapidly

— Liver

— Lung                                                            

— Bone

What are the treatment recommendations

• excisional biopsy

• radiotherapy to primary site (with 5cm margins), in-transit areas and draining lymph nodes (standard)

• no role for elective node dissections, ? role sentinel node biopsy

• radiotherapy alone in advanced or inoperable cases

• palliative chemotherapy for metastatic disease

• current TROG trial on chemoradiotherapy

What is the recommended treatment

• The primary lesion is confirmed by biopsy and treatment is by WLE with 2-3cm margins with histologically negative margins confirmed

• Involved field XRT appears to reduce local recurrence rates

• therapeutic lymph node dissection for positive nodes followed by XRT

• For clinically negative draining nodal basin, SLNB is performed to identify clinically occult nodes (30%)

• Little evidence to support adjuvant chemo

• radiotherapy alone in advanced or inoperable cases

• palliative chemotherapy for metastatic disease

• current TROG trial on chemoradiotherapy

What are the poor prognostic factors

Age <60

H&N, Trunk

Male

Local /regional recurrence