Growing nevi
The frequency of growing nevi is inversely related to age, thus they are common in patients younger than 20 years (12-58 % of clinically examined nevi) and rare in older age groups (1-5%). In the absence of clinical signs of atypia, enlargement alone does not indicate malignancy. The characteristic dermoscopic feature of growing nevi is the peripheral rim of brown globules. Follow-up of nevi with a peripheral rim of globules will reveal symmetric enlargement and once those nevi reach senescence, peripheral globules will no longer be visible.[1]
Reticular nevi and globular/cobblestone nevi present differences in epidemiology and morphology. This had led to the consideration of the two distinct pathways of nevogenesis.[2] According to this “dual concept of nevogenesis”, nevi with a globular/cobblestone pattern represent dermal melanocytic proliferations that develop during early childhood and persist throughout life. In this group, small congenital melanocytic, compound and dermal nevi are included. In contrast, reticular nevi are predominantly epidermal proliferations of melanocytes and present a dynamic life cycle. They are first developing during puberty, increasing in number until the 5th decade of life and, as a result of progressive involution or regression, decrease in number at older age. [3][4].
Dermoscopic Pattern of Growing Nevi
Dermoscopic studies demonstrated that growing nevi typically reveal a peripheral rim of small, homogenously sized, brown globules. These globules correspond to small junctional nests of melanocytes at the tips of the rete ridges and most commonly appear at the border of junctional or compound nevi.[5].
Reticular Nevi with Peripheral Globules
Reticular nevi tend to develop at puberty (age 14–25 years), which explains why peripheral globules are most commonly observed in young adults. Reticular Nevi typically grow symmetrically and horizontally, resulting from the peripheral extension of small globules together with the progressive appearance of reticular pattern within the central part of the nevus. Once the nevus enters senescence, peripheral globules disappear and the entire nevus reveal a reticular pattern.[6].
Globular and Cobblestone Nevi
Globular and cobblestone nevi represent primary dermal melanocytic proliferations and are the hallmark of small congenital melanocytic, compound, and intradermal nevi. {Marghoob, 2012}
In contrast to reticular nevi, signs of growth in globular or cobblestone nevi are not recognizable. These nevi tend to enlarge symmetrically. Follow-up data of globular or cobblestone nevi is lacking, but clinicians suspect that after initial proliferation of dermal melanocytes during early childhood, most globular nevi will either maintain their clinical and dermoscopic appearance throughout life, or undergo the typical development of dermal nevi; loss of pigmentation.[7].
Globular - Reticular Nevi
This nevus type typically shows a central brown to gray structureless pattern and reveals overlapping growth patterns of reticular nevi and globular nevi. Globular-reticular nevi may appear with the peripheral rim of globules that eventually results in the expansion of the network at the periphery of the lesion. Exact morphologic data about the further growth patterns are lacking, but based on clinician’s experiences, the central part becomes more elevated and progressively loses pigmentation.[8].
Nevi in Pregnancy
An interesting observation is that naevi with peripheral globules are not only most prevalent in young adolescence but also prevalent during pregnancy. One explanation for the increased frequency of growing naevi could be the growth hormone rich environment in both periods. Another explanation for the higher prevalence of naevi with peripheral globules among youth is its temporary nature and, among elderly, these naevi transform into reticular or reticular-mixed patterns. The finding of a similar anatomic site related distribution for the different types of naevi is in line with this hypothesis [9].
Frequency of histologic atypia in enlarging nevi
Kittler et al. analyzed the histological features of enlarging nevi (n = 40) and demonstrated that enlarging nevi in children and adolescents never had histological signs of atypia (n = 13). In older age groups, 48.1% of excised enlarging nevi (n = 27), which were clinically diagnosed as common nevi, showed histological signs of atypia. In this study, none of the excised enlarging lesions was histologically diagnosed as melanoma. [1]
- ↑ 1.0 1.1 Kittler et al.: Frequency and characteristics of enlarging common melanocytic nevi. Arch Dermatol 2000;136:316-20. PMID: 10724192.
- ↑ Zalaudek et al.: Age distribution of biopsied junctional nevi--Unna's concept versus a dual concept of nevogenesis. J. Am. Acad. Dermatol. 2007;57:1096-7. PMID: 18021858. DOI.
- ↑ Kincannon & Boutzale: The physiology of pigmented nevi. Pediatrics 1999;104:1042-5. PMID: 10506262.
- ↑ An Atlas of Dermoscopy, Second Edition. Marghoob A. et al. CRC Press; 2012.
- ↑ An Atlas of Dermoscopy, Second Edition. Marghoob A. et al. CRC Press; 2012.
- ↑ An Atlas of Dermoscopy, Second Edition. Marghoob A. et al. CRC Press; 2012.
- ↑ An Atlas of Dermoscopy, Second Edition. Marghoob A. et al. CRC Press; 2012.
- ↑ An Atlas of Dermoscopy, Second Edition. Marghoob A. et al. CRC Press; 2012.
- ↑ Zalaudek et al.: Frequency of dermoscopic nevus subtypes by age and body site: a cross-sectional study. Arch Dermatol 2011;147:663-70. PMID: 21690528. DOI.
