Sunday, January 18

Melanocytic nevus

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what is melanocytic nevus?
Melanocytic nevus is the medical term for mole, a pigmented lesion on the body.
Melanocytic nevus is also known as nevocytic nevus. It is the benign proliferation of a variant of melanocytes known as nevus cells. The nevus cells are larger than the typical melanocytes. They lack dendrites and have copious cytoplasm with coarse granules.

The melanocytes are pigment producing cells, having dendrites for transferring melanosomes containing melanin pigment to keratinocytes (cells forming outer layer of skin). These variant melanocytes are the primary component of a melanocytic nevus. They may occupy the junction between epidermis and dermis or the dermis of the skin. They may migrate towards epidermis or move deeper down into dermis.

Types of melanocytic nevi

Depending upon the location, the nevi are variously classified as junctional, intramucosal, compound, Ota, simplex, intradermal, Spitz or blue nuvi. The atypical (dysplastic) mole appear different from other moles and most of the melanoma arise from them. Further the mole may be present at birth (congenital) or acquired later in life.
congenital mole
melanocytic nevus on the nose

Junctional melanocytic nevus

The junctional mole is located along the junction of epidermal and dermal skin layers. These moles usually appear flat or slightly raised. They are usually acquired lesions. As they age they may become compound moles and become increasingly papular. Depending upon the depth and density and number of cells involved they may range in color from brown to black. There is slight risk of these moles turning into melanoma. Junctional intramucosal lesions are found usually in the mouth or genital area.

Intradermal melanocytic nevus

The intradermal moles are extremely common type of moles and are located in the dermis. They are flesh colored. Though there is proliferations of melanocytes, because of their depth from skin surface, the skin does not appear colored. These intradermal lesions appear usually as small, raised, round, dome-shaped or wart-like growths on the skin. If they are of recent origin or appear to grow fast, differential diagnosis is required to rule out basal cell carcinoma.

Compound melanocytic nevus

The compound mole represents the melanocyte proliferation of junctional as well as intradermal origins. These compound nevi are slightly raised and appear light brown to dark brown. They may be present at birth or appear later in life. If there is enlargement or symptomatic changes in compound lesion medical examination is required.

Congenital moles are present at birth or appear soon after birth.
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They are anomaly in embryogenesis and are considered as malformations or hamartomas. These lesions can be small or very large. Giant pigmented nevi are large dark colored lesions. Nearly 10 to 15% of these giant moles can develop into melanoma. The risk of melanoma increases with the increase in the size of the congenital mole.

Nevus of Ito or Ota are congenital moles appearing on the face and shoulder. Blue nevus and mongolian spots are also deep hyperpigmentation patches which are congenital. Congenital moles are sometimes associated with halo or vitiligo. Nath AK. et al reported a case where the congenital mole started regressing when the patient developed hypopigmentation at a different site. Lymphocytic infiltration and loss of pigment production was observed in the area of mole regression.

Acquired melanocytic nevus

Acquired moles appear later in life and are considered as benign neoplasms. Acquired moles may of junctional, compound or intradermal types. They are believed to be caused by sun exposure. In fair persons the sunburn areas can develop into these lesions.

Dysplastic (atypical) melanocytic nevus

Dysplastic moles are atypical and tend to have irregular borders and irregular coloration. These atypical moles may be flat or raised. When a number of atypical lesions are present, medical help must be sought to rule out melanoma, a virulent form of skin cancer. Atypical mole syndrome is an hereditary condition.

Causes
The cause of congenital moles is considered to be a defect in embryological development or hereditary condition. Sun damage, overexposure to sunlight and the resultant premature aging of skin are believed to be the causes of acquired moles.

Management
The melanocytic nevi may be left alone. If there is cosmetic or other concern they may be removed either by surgery or by medical lasers. A raised mole may also interfere with daily life chores like shaving or dressing. If there are any remnants of the lesion after the removal, it may regrow. If the mole is growing fast, if it is crusting and oozing, if there is any familial incidence of skin cancer or a number of atypical melanocytic nevi are present, immediate medical help is to be sought to rule out melanoma.
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Reference:
1.Arpaia N, Cassano N, Filotico R, Laricchia F, Vena GA. Unusual clinical presentation of regression in a congenital melanocytic nevus. Dermatol Surg 2005;31:471-3.
2.Martín JM, Jordá E, Calduch L, Alonso V, Revert A. Progressive depigmentation of a palmar congenital melanocytic nevus without an associated halo phenomenon. Dermatology 2006;212:198-9.
3. Nath AK, Thappa DM, Rajesh NG. Spontaneous regression of a congenital melanocytic nevus. Indian J Dermatol Venereol Leprol 2011;77:507-10
4.Gass JK, Grant JW, Hall PN, Atherton DJ, Burrows NP. Clinical resolution of a neonatally eroded giant congenital melanocytic nevus. Pediatr Dermatol 2006;23:567-70.
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Image source: en.wikipedia.org/wiki/File:Congenital_melanocytic_nevus_01.jpg
Author: M. Sand, D. Sand, C. Thrandorf, V. Paech, P. Altmeyer, F. G. Bechara.
License: CC BY 2.0
Current topic in natural skin care: Melanocytic nevus.
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1 comment:

Shreya at Jumbodium said...

Very informative post. People facing such issue should be aware of the causes and precautions as well. Thank u for the wonderful share.