How many forms of malignant melanoma exist?

There are four main types of melanoma, each with its own unique characteristics and prognosis:

1. Superficial spreading melanoma (SSM): This is the most common type of melanoma, accounting for about 70% of all cases. SSM typically begins as a small, flat, pigmented spot that can grow and change shape over time. It is often found on sun-exposed areas of the skin, such as the back, legs, and arms.

2. Nodular melanoma (NM): NM is the second most common type of melanoma, accounting for about 15% of all cases. NM typically begins as a small, raised, firm bump that can grow quickly. It is often found on the trunk, head, and neck.

3. Lentigo maligna melanoma (LMM): LMM is a rare type of melanoma that accounts for about 5% of all cases. LMM typically begins as a small, flat, pigmented spot that can grow slowly over time. It is often found on sun-exposed areas of the skin, such as the face, arms, and legs.

4. Acral lentiginous melanoma (ALM): ALM is a rare type of melanoma that accounts for about 5% of all cases. ALM typically begins as a small, flat, pigmented spot on the palms of the hands, soles of the feet, or under the nails.