Nevogenesis-New Thoughts Regarding a Classical Problem

Abstract

The development of melanocytic nevi is a multifactorial and heterogeneous biologic process that involves prenatal and postnatal steps. As a consequence, there are two main perspectives to nevi: that of a hamartoma and that of a benign tumor. In this review, dermatopathological studies on congenital and acquired nevi, including studies on age-related and location-dependent changes, are analyzed. These studies have lead to different hypothetical concepts on the evolution of individual lesions. In the light of findings from experimental embryology and stem cell biology, we discuss the histogenesis of nevi with special reference to the temporospatial sequence of melanocyte-basement membrane interactions and hair follicle genesis. Regarding the mechanisms of postnatal nevus development, epidemiological studies demonstrate the importance of constitutional and environmental influences, especially ultraviolet light. Possible molecular pathways of solar nevogenesis involve ultraviolet-induced alterations of the cellular microenvironment (eg, changes in the expression of cytokines and melanocyte adhesion molecules). Recent results and future directions of clinical and experimental research are presented.

Symmetric Plantar Melanocytic Nevi - Site-Specific Phenomenon or Pure Chance

“…Certain types of keratin (K6, K9, K16, K17) are specifically expressed in palmoplantar skin [9]. An influence of the epidermal or adnexal microenvironment on nevogenesis is possible, but not well-established [10]. The rare entity of epidermolysis-bullosa-nevi might represent a link between an epithelial skin disease and nevogenesis; however, this eruption is more likely related to components of the blister fluid or to secondary inflammatory changes [11].…”

Benign Squamous and Melanocytic Tumors

“…A melanocytic nevus is considered as a hamartoma or a benign tumor of neural crest-derived melanocytes [ 19 ]. An eyelid nevus, as in other areas of the skin, can be acquired (usually) or congenital.…”

“…3.12 ) to the dermal only location (intradermal nevus) (Fig. 3.13 ), refl ecting the process of nevogenesis [ 19 ]. Junctional nevi are most frequent in the fi rst decade, compound nevus in the second decade, and the proportion of dermal nevi increases with age [ 44 ].…”

Congenital Melanocytic Nevi

“…Krengel el al. [ 6 ] postulate that from birth to adulthood, the area of the head grows by a factor of 2.8, trunk and arms by a factor of 8, and legs by a factor of 12. With this criterion they are subdivided into three groups based on their size: small (<1.5 cm), medium (1.5-20 cm), and large or giant (>20 cm) in their projected adult size.…”