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Congenital melanocytic nevi
Last reviewed: 17.10.2021
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Congenital melanocytic nevi (syn: birthmarks, giant pigmented nevi) - melanocytic nevus, existing since birth. Small congenital nevuses do not exceed 1.5 cm in diameter. Large neovuses are considered to be more than 1.5 cm in diameter. Giant congenital nevuses occupy a whole segment of the body surface.
Congenital melanocytic nevuses rise above the skin level, sometimes so insignificant that it is noticeable only when viewed in transmitted light. They are often unevenly pigmented, often have uneven terrain, they can palpably define more compact, often hyperpigmented, knotty areas and areas of softer consistency. Usually such nevi are covered with hard hair. With age, they can grow in size, their coloring sometimes turns pale; it is possible to develop perinevous vitiligo.
[Pathomorphology
Congenital nevi are usually mixed. Characterized by a deep localization of non-empty cells, down to the lower third of the mesh layer of the dermis, and the involvement of the epidermis of the appendages of the skin - hair follicles, sweat glands, and muscles that lift hair. It is possible to detect nests of nevus cells inside or around the vessels. Some congenital nevuses of small size can not histologically differ from the usual nevi.
In giant congenital nevi, penetration of melanocytes into the subcutaneous tissue and even fascia is determined. Possible focal proliferation of Schwann cells by type of neurofibroma, focal cartilaginous metaplasia.
Histogenesis
Giant congenital nevi are considered as hamartomas of complex structure.
Basal cell nevus syndrome
The syndrome of basal cell nevuses (synovial Gorlin-Goltz syndrome) is inherited autosomal dominant, characterized by five main symptoms: multiple surface basaliomas, often quite quickly taking an aggressive character; cysts of jaws with epithelial lining; various abnormalities of the skeleton, especially the ribs, skull and spine; ectopic calcification; small depressions (1 - 3 mm) on the palms and soles,
Histological examination of the depressions revealed acanthosis, hyperkeratosis at their edges, thinning of the stratum corneum in the center, proliferation of basal cells at the base.