What are Atypical Nevi

Onset: begin to appear during early childhood. The characteristic features of atypical moles are present at the time of puberty. Unlike common acquired melanocytic nevi, which stop appearing after age 30, atypical nevi continue to appear well into adulthood.
Size: ranging from 6 mm-15 mm in diameter.
Border: irregularly outlined, indistinct, and fades imperceptibly into the surrounding skin.
Color: variegated with a haphazard mixture of pink, tan, brown, and black.
Surface: irregular, often with a central or eccentric papule surrounded by a prominent macular component.
Site: anywhere in the skin but occur most commonly on the trunk and upper extremities. Affected persons often have nevi in sun-protected areas, such as the scalp, groin, buttocks, the breasts in women, and the palms and soles.
Progression: increased risk of melanoma, most often the superficial spreading type.

What are Congenital Melanocytic Nevi

Incidence: About 1% of newborns have at least one melanocytic nevus.

Onset: Present at birth, or appearing by age 2.

Course: The vast majority of congenital melanocytic nevi are benign and follow a life-long course of maturation. They increase in size and become more heavily pigmented during puberty.

Size: Congenital melanocytic nevi vary greatly in size.

Appearance: Congenital melanocytic nevi are considered to be a type of birthmark, of which there are many variants. They are usually dark brown and raised, with an irregular verrucous surface. Most have increased coarse terminal hairs.

Symptoms: Depending on their location, large lesions may be disfiguring.

Diagnosis: Depending on their onset, course and appearance, most congenital nevi are diagnosed. Nevi which deviate from the urdinary pattern of maturation are suspicious and biopsy is warranted.

Histopathology: Congenital nevi are benign skin tumors composed of melanocyte-derived nevus cells, they are usually compound nevi with nested nevus cells at the junction and also in the dermis. Nevus cells may extend into fat and invest adnexal structures and blood vessels.

Progression: The risk of malignant transformation is increased in giant congenital melanocytic nevi with diameters greater than 20 cm with a lifetime risk of 5-8%. Melanoma developing in smaller congenital nevi may have an increased lifetime risk in those larger than 2 cm.

Treatment: Nevus cells in congenital nevi often extend into subcutaneous fat, therefore a malignant change may not be easily detected. For this reason, elective excision when feasible (usually around the time of puberty) is favored.
















Melanoma developing in a congenital nevus

What is Becker’s Nevus

Becker’s Nevus
Origin: a developmental anomaly, lacks nevus cells
Onset: lesions appear in adolescent men
Site: on the shoulder, submammary area, and upper and lower back
Appearance: either a brown macule, a patch of hair, or both; nonhairy lesions may later develop hair. The border is irregular and sharply demarcated.
Size: varies in size and may enlarge to cover the entire upper arm or shoulder
Treatment: usually too large to remove by excision. The hair may be shaved
Progression: Malignancy has never been reported
Associated lesions: other developmental defects such as ipsilateral hypoplasia of breast and skeletal anomalies including scoliosis, spina bifida occulta, or ipsilateral hypoplasia of a limb in Becker nevus syndrome.

What are Halo Nevi

Onset: occur primarily during adolescence. The average age of onset is 15 years.
Course: The halo usually re-pigments over a few years. Focal atypical nevus cells may be seen though the majority of the pre-existing nevi are benign.
Prevalence: 1% of the population
Site: located on the trunk; they never occur on palms and soles.
Appearance: The depigmented halo is symmetric and round or oval with a sharply demarcated border.
Development: Primary: may occur as an isolated phenomenon or Secondary: several nevi may spontaneously develop halos. A pre-existing nevus develops a surrounding rim of hypopigmentation that heralds the gradual disappearance of the nevus over several months.
Significance: Halo nevi appear to be a host response directed against the nevus cells.
Associated Lesions: Halo nevi also occur in people with vitiligo. A halo may rarely develop around malignant melanoma, but in such instances it is usually not symmetric.
Implications: People with halo nevi should have a full skin examination to look for vitiligo and also to screen for melanoma.
Diagnosis: Woods light accentuates the halo. Skin biopsy shows a junction or compound nevus surrounded by a dense infiltrate of lymphocytes. There are no melanocytes in the halo area.
Treatment: Removal of a halo nevus is unnecessary. If the nevus itself has atypical features, a conservative excision in which the mole part of a halo nevus may be removed by shave or excision.















A halo around a malignant melanoma

What is a Spitz Nevus

Site: most often occurs on the face, scalp or legs of pre-adolescent children.

Onset: most common in children, but does appear in adults.

Course: They appear suddenly and, contrary to slowly evolving common moles. The lesion and its biologic course are benign.

Appearance: hairless, dome-shaped papules or nodules, usually solitary but may be multiple.

Surface: a smooth or warty surface

Size: vary in size from 0.3 to 1.5 cm.

Color: red to reddish-pink caused by increased vascularity
Complications: bleeding sometimes follows trauma.
Diagnosis: Skin biopsy reveals overall architectural order with nested spindle-shaped nevus cells (A cell of a pigmented skin mole whose absence of dendrites differentiates from a melanocyte) and areas with large pleomorphic nevus cells. Such changes would be worrisome for melanoma in an adult. Histologic differentiation from melanoma is sometimes difficult.

Treatment: should be removed for microscopic examination, complete excision to minimize the risk of recurrence and associated pleomorphism.