Most common type of melanoma
**Core Concept**
The most common type of melanoma is a type of skin cancer characterized by the uncontrolled growth of melanocytes, the cells responsible for producing pigment in the skin. This type of melanoma arises from the epidermis, the outermost layer of the skin, and is often associated with UV radiation exposure.
**Why the Correct Answer is Right**
The correct answer is **Superficial Spreading Melanoma (SSM)**, which accounts for approximately 70% of all melanoma cases. This type of melanoma typically presents as an asymptomatic, flat or slightly raised, pigmented lesion with an irregular border and variable color. SSM often arises from the horizontal growth phase of melanocytic neoplasia, where melanocytes proliferate at the dermo-epidermal junction. The horizontal growth phase is characterized by the formation of a radial growth phase (RGP), where melanocytes grow along the epidermal-dermal junction, eventually forming a vertical growth phase (VGP), where melanocytes invade into the dermis.
**Why Each Wrong Option is Incorrect**
**Option A:** **Nodular Melanoma** is a more aggressive form of melanoma, accounting for approximately 15-30% of cases, and is characterized by a vertical growth phase from the onset.
**Option B:** **Acral Lentiginous Melanoma** is a rare type of melanoma that occurs on the palms, soles, or under the nails, and is more common in individuals with darker skin types.
**Option C:** **Lentigo Maligna Melanoma** is a type of melanoma that occurs on sun-damaged skin, typically in older adults, and is characterized by a radial growth phase.
**Clinical Pearl / High-Yield Fact**
It's essential to remember the "ABCD" rule for melanoma diagnosis: Asymmetry, Border irregularity, Color variation, and Diameter > 6mm. This rule can help identify potentially malignant lesions.
**Correct Answer:** C. Lentigo Maligna Melanoma