Which stage of malignant melanoma is characterized by a prolonged horizontal growth phase?

The superficial spreading type of malignant melanoma is characterized by a prolonged horizontal growth phase. This type is the most common form of melanoma and typically appears as a flat or slightly elevated lesion that has irregular borders and variations in color. The horizontal growth phase allows the melanoma to spread along the surface of the skin, often for a significant period before penetrating deeper tissues.

This particular stage is especially critical because it provides an opportunity for early detection and intervention, which can significantly improve outcomes. The extended horizontal phase can lead to increased awareness among patients and healthcare providers, making it more likely for lesions to be noticed and evaluated earlier than in other more aggressive forms of melanoma.

In contrast, other melanoma types, such as nodular melanoma, often have a more aggressive vertical growth phase from the outset, making them more dangerous as they can invade deeper tissues more quickly. Similarly, acral lentiginous and lentigo melanoma types also have distinct characteristics and growth patterns that distinguish them from the superficial spreading type.