What is a birthmark?

A birthmark is a localized multiplication of pigment cells of the skin (melanocytes), which appears as a dark spot. Colloquially, the terms beauty spot and mole are also used. The technical term for a birthmark is nevus (plural nevi). The number of birthmarks increases with age. New moles can appear up to the age of forty. Pigmented spots that appear at an advanced age are called age spots. An ordinary birthmark is usually smaller than about 5 millimeters in diameter. It is round or oval, light brown to dark brown. A birthmark has a smooth surface and is sharply distinguishable from the surrounding skin. Birthmarks occur particularly frequently on body parts that have been exposed to the sun. Depending on their hereditary disposition, an adult Central European develops on average 10 to 40 birthmarks over two millimeters in diameter on the entire body. From a number of 50 moles on, there is a slightly increased risk of skin cancer (Garbe C. et al. 1994, J Invest Dermatol). The risk of a birthmark developing into skin cancer is low. Calculated over a period of one year, the risk is between 1:200,000 and 1:33,000 depending on age (Cymerman RM, et al., 2016, J Natl Cancer Inst). In more than 70 percent of cases, black skin cancer develops in places where no birthmark is present (Pampena R., et al., 2017, J Am Acad Dermatol).

How does a birthmark appear?

The origin of the pigment cells can be traced back to the first weeks of the unborn child. Under the influence of messenger substances, the cells from the region of the future spinal cord (also called neural crest) develop into connective tissue cells, cartilage cells, nerve cells and pigment cells. Certain messenger substances initiate the development from precursor cells to pigment cells. UV light can change the genetic material in pigment cells. Certain changes in the genetic material lead to the proliferation of pigment cells, which become visible as moles (Grichnik JM, et al., 2014, Exp Dermatol).


How are moles divided?

Skin marks are classified according to the age at which they appear. Congenital moles occur in the womb or in the first weeks of life. Moles that develop in childhood and later are called acquired moles. Pigment marks that develop after the age of 40 are age spots.

Moles are also distinguished according to their location in the layers of the skin. A birthmark that appears at the boundary layer between the epidermis and the dermis is called a junctional nevus. If pigment cells are found in both the epidermis and the dermis, it is called a compound nevus. The technical term for a birthmark whose pigment cells are only found in the dermis is dermal nevus.

The arrangement of the pigment cells in the skin is examined with a special magnifying glass (dermatoscope). The arrangement of the pigment cells can be divided into patterns such as lines, plaques, circles or dots. Moles on the palms of the hands or soles of the feet show parallel lines in the furrows of the skin (Kittler H., 2015, Dermatoscopy: Pattern analysis of pigmented and unpigmented skin lesions). Other features that help to differentiate between pigment spots are color, size and the site of the birthmark.

What types of pigmented spots are there?

The most common types of pigmentation spots are:

  • Freckles (ephelids).
  • Liver spot (Lentigo simplex, age spot: Lentigo solaris).
  • Acquired birthmark (nevus of the junctional type, the compound type or the dermal nevus).
  • Congenital birthmark (congenital nevus cell nevus).
  • Cafe au Lait spot (pigment nevus).

Among the rare special forms are:

  • Blue nevus (Naevus caeruleus).
  • Halo or sutton nevus.
  • Spitz nevus (spindle cell and epithelioid cell nevus).
  • Reed nevus (spindle cell nevus).
  • Spilus nevus.
  • Becker nevus.
  • Large congenital mole on the face (Ota nevus).
  • Large congenital mole on the shoulder (nevus Ito).

What is a conspicuous skin mole (atypical or dysplastic nevus)?

The unusual appearance of atypical nevi can be distinguished from birthmarks using the ABCDE rule. Even when looking at the individual cells under the microscope, changes can be seen in comparison to normal moles. Atypical moles only appear during or after puberty. They are often larger than 6 millimeters in diameter, raised or irregularly patterned. People with fair skin, red or blond hair, blue or green eyes and freckles are particularly at risk. Sunburn, especially during childhood, increases the risk of developing atypical moles.

Atypical moles occur in Europe in about 10 percent of the population (range: 7-24 percent) (Tucker M.A., 2009, Hematol Oncol Clin North Am). It is assumed that the risk of developing skin cancer increases with the number of atypical moles (Gandini S., et al., 2005, Eur J Cancer). The risk of developing black skin cancer in conspicuous moles is estimated to be approximately 1:30,000 to 1:40,000 (Tsao H., et al., 2003, Arch Dermatol).

It is therefore recommended to remove conspicuous moles without leaving any residue (Winkelmann R.R., et al., 2015, J Am Acad Dermatol. 2015).

Which birthmark is dangerous?

Skin cancer or precancerous lesions are conspicuous by certain features. The ABCDE rule helps to detect suspicious moles. Each letter stands for a characteristic. If at least one of these features is present, an examination by a dermatologist (dermatologist) should be performed.

  • A = Asymmetry: uneven shape of the birthmark.
  • B = Boundary: irregular or blurred edges, without a clear demarcation to the healthy surrounding skin.
  • C = Coloration: different coloration with light, dark or pink parts.
  • D = Diameter: at the widest point there is a diameter of more than 6 millimeters.
  • E = Development / elevation: changes in size, shape or color / growth above the skin level.

Moles on the sole of the foot or on the mucous membranes are often overlooked during self-examination. Moles that itch or bleed should also prompt an examination by a dermatologist.

What is a congenital birthmark?

Congenital birthmarks are skin spots that are present at birth or develop within the first weeks of life. Congenital birthmarks are dark and occasionally hairy. They can be slightly raised and have a variety of colors, from light brown to black. Congenital moles grow in proportion to the growth in size of the human being. They consist of densely packed pigment cells. In technical terminology, they are called congenital melanocytic nevus. Congenital birthmarks occur in 1 in 100 newborns. They occur somewhat more frequently in women than in men (ratio of 3:2). In congenital birthmarks, the pigment cells are located in the dermis.

The birthmarks are divided according to their size:

  • Small: less than 1.5 centimeters
  • Medium: 1.5 to 20 centimeters.
  • Large: 20 to 40 centimeters.
  • Huge: larger than 40 centimeters.

The larger the congenital birthmark, the greater the risk of degeneration into skin cancer (Kinsler VA, et al., 2017, Br J Dermatol). The risk for small congenital birthmarks to develop skin cancer in the course of a lifetime is about one percent (Caccavale S., et al., 2020, Dermatology). The risk of the general population in Europe to develop malignant melanoma over a lifetime is 0.3 to 1.6 percent (Erdmann F, et al., 2013, Int J Cancer).

Removing birthmarks without surgery

Moles can be removed in different ways. In certain cases a birthmark can be lasered away. With the laser, high-energy light is transmitted to the skin. For fractions of a second, the tissue is strongly heated. Individual tissue layers or cells are vaporized or charred.

Some lasers transfer the energy to chemical compounds with a specific color (hemoglobin, melanin, water). This allows pigment cells to be destroyed in a targeted manner while sparing the surrounding tissue. However, these lasers have a limited penetration depth. Pigment cells in deeper skin layers can remain and multiply again. This is particularly dangerous if black skin cancer has not been ruled out with absolute certainty in advance. Lasers also carry the risk of light-colored skin spots appearing if all pigment cells are destroyed. Other lasers, such as the CO2 laser, destroy the most superficial tissue layer without differentiating between color pigments. In 25 to 50 percent of cases, this results in scars, and in up to 18 percent of cases, wounds can become inflamed (Eggen C.A.M., et al., 2018, Br J Dermatol).

The result of a laser treatment depends on the type of birthmark, the skin characteristics of the patient, the characteristics of the laser and the experience of the user. Experts agree that birthmarks must be carefully selected for laser treatment. If a suspicion of cancer cannot be ruled out, a tissue sample must be examined fine-tissue (technical term: histologically) (recommendation of the Radiation Protection Commission, February 2016).

The independent removal of a birthmark at home is strictly discouraged. In the worst case, this can delay the diagnosis of skin cancer.

Von der selbstständigen Entfernung eines Muttermals zu Hause wird strengsten abgeraten. Im ungünstigsten Fall kann dadurch die Diagnose eines Hautkrebses verzögert werden.

The surgical removal of birthmarks

The method of first choice for the safe assessment of suspected cancerous skin lesions is three-dimensional, micrographically controlled removal. The procedures of shaving, scraping or punching out have limited significance in the fine tissue examination. With a gentle treatment of the tissue and a tension-free fine skin suture, a fine line shaped scar usually remains. When planning an operation from an aesthetic point of view, the scar is aligned so that it is hardly visible. Larger congenital moles are removed in several operations so that the skin suture can heal without tension. The plastic surgeon then speaks of a serial excision.


Removing birthmarks on the face

To achieve an aesthetically optimal result, experienced plastic surgeons work with fine instruments and magnifying glasses. The procedure is painless to painless. The anaesthetic is injected with a very fine cannula. The addition of adrenaline to the anesthetic reduces the risk of seeing a bruise after the operation. The removal of a birthmark is performed under local anesthesia and rarely takes longer than fifteen minutes. Experience with microsurgical and plastic surgery techniques ensure that scars are barely visible. The smallest wounds are closed along the skin tension lines with the finest sutures. Under these circumstances the wound can heal without tension and the stitches can be removed after a few days.


What should be considered after the removal of a birthmark?

The wound should be cooled slightly on the first day. Showering is usually possible on the first day after the operation. However, prolonged bathing or swimming should be avoided in the first 2 weeks. A sick leave is usually not necessary. The skin sutures are removed after 5 to 7 days. Wound healing is usually completed after 7 to 10 days. Cigarette smoking delays wound healing and increases the risk of inflammation. After two to three weeks, scar healing can be supported by frequent application of cream. For a particularly inconspicuous scar, we recommend the use of UV protection in the first few months.


What does the removal of a birthmark cost?

The health insurance company pays for the removal of birthmarks if it is medically necessary, i.e. if cancer is suspected. Birthmarks can be removed even if they are aesthetically disturbing. The price for the removal of benign birthmarks depends on the size and position and the number of birthmarks to be removed. You can find an order of magnitude of the prices on our cost page.


Author's statement

Author: Stéphane Stahl, MD, PhD. There are no financial relationships with the pharmaceutical or medical device industries that could have influenced the above text. Any reproduction, even partial, is permitted for personal use only. All texts used on this website are protected by copyright.


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