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