Malignant Melanoma

Skin Pathology 

Definition: Malignant melanoma is the malignancy of melanocytes. This is the only melanoma which has no respect for the time and location (tissues).

Incidence:
I) Increasing at a rapid rate
II) Melanoma peaks in ages 40-70

What are risk factors?

1. Chronic sun exposure,sunburns
2. Dysplastic nervus syndrome
3. Familial melanoma is associated with loss of function mutation of the p16 tumor suppressor gene on chromosome 9.

Gross appearance:

You can use a mnemonic (ABCDE) to memorize its appearance.
Asymetric
Borders; irregular borders
Color; Variegated color (many colors together)
Diameter; large diameter
Evolving; enlarging macule, papule or nodule

Sight of occurrence
Males: upper back
Females: Back and legs

Some important melanomas we should know!

Superficial spreading melanoma:

• Most common type of melanoma
• Has horizontal growth pattern

Lentigo maligna melanoma:

• Usually located on the face or neck of older individuals
• Best prognosis

Acral lentiginous melanoma:

• Most common melanoma is dark skinned individuals
• Affects palms, soles and subungual area

Prognosis
Staging is by depth of invasion (vertical growth)
-Breslow's thickness
-Clark's levels
Let me give you brief knowledge about Breslow's thickness & Clark's levels

Breslow's thickness:
First reported by Alexander Breslow, MD in 1970, the Breslow thickness is defined as the total vertical height of the melanoma, from the very top (called the "granular layer") to the area of deepest penetration in to the skin.
Worse prognosis;
less than 1 mm: 5-year survival is 95% to 100%
1 to 2 mm: 5-year survival is 80% to 96%
2.1 to 4 mm: 5-year survival is 60% to 75%
greater than 4 mm: 5-year survival is 37% to 50%

Clark's levels: how deep the tumor has penetrated into the layers of the skin. This system was originally developed by W. H. Clark, MD back in 1966.
Clark levels are  defined as follows:

Level I: confined to the epidermis (top-most layer of skin); called "in situ" melanoma; 100% cure rate at this stage
Level II: invasion of the papillary (upper) dermis
Level III: filling of the papillary dermis, but no extension in to the reticular (lower) dermis
Level IV: invasion of the reticular dermis
Level V: invasion of the deep, subcutaneous tissue

Treatment

• Wide surgical excision
• Systemic disease is treated with chemotherapy or immunotherapy
• May resolve spontaneously