Which melanoma subtype is the most aggressive and tends to skip the radial growth phase?

• A. Superficial spreading
• B. Nodular
• C. Lentigo maligna
• D. Acral lentiginous

Answer: (B)

A key concept here is how melanoma grows over time and why depth matters for prognosis. The radial growth phase is a horizontal spread of tumor cells within the epidermis and superficial dermis, which often occurs first and can keep the lesion thinner for a period, sometimes allowing earlier detection and treatment. The subtype that stands out for aggressiveness is the one that tends to invade downward into deeper tissues from the start, with little to no radial spread. This early vertical growth leads to a rapid increase in Breslow depth, which is the strongest prognostic factor in melanoma. Because depth can advance quickly, this subtype is more likely to metastasize early and has a poorer overall prognosis. In practice, this means nodular melanoma typically presents as a rapidly enlarging raised nodule and lacks a prolonged radial growth phase, distinguishing it from the other subtypes that show a more prominent horizontal spread before deep invasion.