Pathology of Superficial Spreading Melanoma

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Dermpath-India

"The most common subtype of Melanoma"

Dr Sampurna Roy MD 2022

Superficial spreading melanoma may develop in any part of the body and at any age.

It is commonly noted on the trunk and lower extremities.

Macroscopically, the lesion has a variegated colour and an expanding irregular margin.

Microscopic features:

Histologically, superficial spreading melanoma may be in-situ or invasive.

It is a poorly circumscribed, asymmetrical lesion.

The epidermis may show irregular elongation of rete ridges, hyperkeratosis and parakeratosis.

There is proliferation of atypical melanocytes at all levels in the epidermis.

The tumour cells in superficial spreading melanoma are present singly and in nests.

There is evidence of pagetoid spread in the epidermis (buckshot spread).

The tumour cells in superficial spreading melanoma may be epithelioid, spindle or nevus cell-like in appearance.

The invasive tumour is usually composed of epithelioid-type of cells.

Nuclear pleomorphism is evident and there are atypical mitotic figures.

The superficial adnexal epithelium may be involved.

The differential diagnosis includes extramammary and mammary Paget's disease, squamous carcinoma with pagetoid pattern in the epidermis .

S100 protein and HMB45 stains are positive in melanoma.

Verrucous melanoma is a variant of superficial spreading melanoma and is characterized by prominent epidermal hyperplasia and elongation of rete ridges.