Superficial Spreading Melanoma
This superficial spreading melanoma showed invasion through papillary dermis and approached papillary-reticular dermal interface (Clark Level 3). The vertical (invasive) growth phase of melanomas consists of cohesive nests, clusters, and nodules invading the dermis. The nests are morphologically different than those in the intraepidermal component with great pleomorphism, apoptosis and frequent mitoses. Regression features are usually absent from the tumor base. Vertical growth phase is associated with greater potential for lymphovascular invasion, metastatic spread and adverse prognosis.