SkinCancerNet Article
Common Pigment Changes

People often worry that they may have skin cancer when they spot:

  • A mole surrounded by a ring of depigmentation (halo nevi)

  • Pigment changes that occur during pregnancy

While these changes usually are benign (not cancerous), these should not be ignored because melanoma appears in a great many sizes, shapes, and colors. Any new or changing mole should be examined by a dermatologist since melanoma may initially appear to be a new mole or an existing mole that has changed.

The following provides more information about these two commonly occurring pigment changes.

Halo Nevi
A mole surrounded by a halo of decolorized skin is what dermatologists call a “halo nevus” (“nevi” if more than one mole). Why halo nevi develop is not well understood. However, it is known that halo nevi develop from existing moles and are relatively common benign (non-cancerous) pigmented lesions that tend to develop in childhood, adolescence, and early adulthood. When a halo nevus develops in an older adult, it may indicate the presence of melanoma elsewhere.

Halo nevi occur in skin of all colors and in people of all racial and ethnic backgrounds. As a halo nevus develops, an area of depigmentation appears around the mole over a period of days to weeks. Eventually, the mole takes on a pink to brown color and is surrounded by a halo of depigmentation as shown in the following photos.


Two halo nevi on a
patient's back

 



Halo nevi on the back
of a woman
 




(Photos used with permission of the
American Academy of Dermatology
National Library of Dermatologic
Teaching Slides)
 

 


Close-up of a halo nevus

The mole may eventually regress or disappear, or it may remain unchanged for many years. New halo nevi may appear from time to time.

When to See a Dermatologist About Halo Nevi
Anyone who develops a mole surrounded by a ring of depigmentation should be examined by a dermatologist because halo nevi can be associated with:

  • Vitiligo, a skin condition characterized by patchy depigmentation of the skin

  • Two risk factors for melanoma — atypical moles and a family history of melanoma

  • The presence of a new melanoma (mostly in older adults)

Dermatologists have the training needed to accurately diagnose halo nevi. Typically, treatment is not required; however, a biopsy may be taken to confirm that the mole is benign. Dermatologists also can recommend cosmetic measures that help make halo nevi less apparent.

Pigment Changes During Pregnancy
Moles frequently become larger or darker during pregnancy, especially on the face, nipples, external genitalia, armpits, and thighs. Scientists believe that hormonal changes may be responsible for this increased pigmentation. However, the role that hormones play is not well understood.

While pregnancy is not a risk factor for melanoma, women should perform regular self-examinations of their skin while pregnant as melanoma can develop simultaneously with skin pigment changes common during pregnancy. Melanoma has escaped early detection during pregnancy because women often mistakenly believe the pigment changes that occur during pregnancy are normal and benign (non-cancerous).

If a woman is at increased risk of developing melanoma because of a personal or family history of melanoma, atypical moles, or another factor that increases her risk, she should tell her obstetrician so that the doctor can consider this during her regular pre-natal checkups. Any woman at high risk for developing melanoma also should have regular skin examinations by a dermatologist while pregnant.

The following photos show melanoma that developed or was detected in pre-existing moles during pregnancy.


 


 

A 28-year old woman noticed this
pre-existing mole enlarge and darken during her second trimester. A biopsy revealed melanoma.
 
A 35-year old woman watched this
pre-existing mole on her back grow
larger and darker during her third trimester. Six months after giving birth,
the mole was removed, and the biopsy confirmed that it was a melanoma.

(Photos used with permission of the American Academy of Dermatology
National Library of Dermatologic Teaching Slides)


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