Which type of nevus is most commonly found in the first two decades of life?

The Spitz nevus is most commonly found in the first two decades of life, typically presenting in children and young adults. This type of nevus is characterized by its often dome-shaped appearance, bright pink to red color, and can sometimes resemble melanoma, making it important for clinicians to recognize its distinct features. While Spitz nevi can still be seen in older individuals, their peak incidence is observed in younger populations, which sets them apart from other types of nevi that may appear later in life.

In contrast, dermatofibromas commonly occur in adults, particularly in young or middle-aged women, and are usually associated with previous trauma. Blue nevi, while also benign, tend to manifest in all age groups, including adults and older individuals, rather than specifically in the younger population. Similarly, compound nevi can occur at various life stages but are generally more prevalent in older children and adults as they tend to develop over time. These differences in age prevalence highlight why the Spitz nevus is the correct answer for a nevus commonly found in the first two decades of life.