differential diagnoses of pigmented skin lesions, including nevi, showing the relative incidence of biopsied lesions, and their malignancy potential. Clinical diagnosis can be made with the naked eye using the ABCD guideline or by using dermatoscopy. An online-screening test is also available to help screen out benign moles. File:Dermatoscope1.A dermatoscope. File:Dermatoscope.A modern polarized dermatoscope. Classification<unk>  nevi can mainly be classified by depth, being congenital versus acquired, and/or specific dermatoscopy or histopathology patterns: ;Depth: Depth class Location of nevus cells Other characteristics Image ICD Junctional nevus Along the junction of the epidermis and the underlying dermis. May be colored and slightly raised. 190px ICD10: D22ICDO: M8740/0 Compound nevus Both the epidermis and dermis. 190px ICD10: D22 (ILDS D22.L14)ICDO: 8760/0 Intradermal nevus Within the dermis. A classic mole or birthmark. It typically appears as an elevated, dome-shaped bump on the surface of the skin. 190px File:Histopathology of a dermal nevus.Small dermal nevus, with nests of nevus cells (arrows) ;Congenital versus acquired: *Congenital nevus: Small to large nevus present at or near time of birth. Small ones have low potential for forming melanomas, however the risk increases with size, as in the giant pigmented nevus. *Acquired nevus: Any<unk>  that is not a congenital nevus or not present at birth or near birth. ;Specific dermatoscopy or histopathology patterns: Type Characteristics Photo-graphy Histo-pathology Dysplastic nevus Usually a compound nevus with cellular and architectural dysplasia. Like typical moles, dysplastic nevi can be flat or raised. While they vary in size, dysplastic nevi are typically larger than normal moles and tend to have irregular borders and irregular coloration. Hence, they resemble melanoma, appear worrisome, and are often removed to clarify the diagnosis. Dysplastic nevi are markers of risk when they are numerous, such as in people with dysplastic nevus syndrome. According to the National Institute of Health (NIH), doctors believe that, when part of a series or syndrome of multiple moles, dysplastic nevi are more likely than ordinary moles to develop into the most virulent type of skin cancer called melanoma. left In this case, the central portion is a complex papule, and the periphery is macular, irregular, indistinct and slightly pink. 180px Characteristic rete ridge bridging, shouldering, and lamellar fibrosis. H&E stain. Blue nevus It is blue in color as its melanocytes are very deep in the skin. 140px left Characteristic pigmented melanocytes between bundles of collagen. H&E stain. Spitz nevus A distinct variant of intradermal nevus, usually in a child. 180px They are raised and reddish (non-pigmented). left Characteristic vertically arranged nests of cells ("hanging bananas"). H&E stain. Giant pigmented nevus Large, pigmented, often hairy congenital nevi. They are important because melanoma may occasionally (10 to 15%) appear in them. 180px 180px Nevus of Ito and nevus of Ota Congenital, flat brownish lesions on the face or shoulder. left Nevus of Ito. Mongolian spot Congenital large, deep, bluish discoloration which generally disappears by puberty. It is named for its association with East Asian ethnic groups but is not limited to them. 150px ;Recurrence: *Recurrent nevus: Any incompletely removed nevus with residual melanocytes left in the surgical wound. It creates a dilemma for the patient and physician, as these scars cannot be distinguished from a melanoma. Differentiation from melanoma It often requires a dermatologist to fully evaluate moles. For instance, a small blue or bluish-black spot, often called a blue nevus, is usually benign but often mistaken for melanoma. Conversely, a junctional nevus, which develops at the junction of the dermis and epidermis, is potentially cancerous. A basic reference chart used for consumers to spot suspicious moles is found in the<unk> emonic A-B-C-D, used by institutions such as the American Academy of Dermatology and the National Cancer Institute. The letters stand for asymmetry, border, color, and diameter. Sometimes, the letter E (for elevation or evolving) is added. According to the American Academy of Dermatology, if a mole starts changing in size, color, shape or, especially, if the border of a mole develops ragged edges or becomes larger than a pencil eraser, it would be an appropriate time to consult with a physician. Other warning signs include a mole, even if smaller than a pencil eraser, that is different from the others and begins to crust over, bleed, itch, or become inflamed. The changes may indicate developing melanomas. The matter can become clinically complicated because mole removal depends on which types of cancer, if any, come into suspicion. A recent and novel method of melanoma detection is the "ugly duckling sign" It is simple, easy to teach, and highly effective in detecting melanoma. Simply, correlation of common characteristics of a person's skin lesion is made. Lesions which greatly deviate from the common characteristics are labeled as an "ugly duckling", and further professional exam is required. The "little red riding hood sign", suggests that individuals with fair skin and light colored hair might have difficult-to-diagnose melanomas. Extra care and caution should be rendered when examining such individuals as they might have multiple melanomas and severely dysplastic nevi. A dermatoscope must be used to detect "ugly ducklings", as many melanomas in these individuals resemble non-melanomas or are considered to be "wolves in sheep clothing". These fair skinned individuals often have lightly pigmented or amelanotic melanomas which will not present easy-to-observe color changes and variation in colors. The borders of these amelanotic melanomas are often indistinct, making visual identification without a dermatoscope very difficult. People with a personal or family history of skin cancer or of dysplastic nevus syndrome (multiple atypical moles) should see a dermatologist at least once a year to be sure they are not developing melanoma.
Melanocytic nevus
Palisaded encapsulated neuroma
Eccrine nevus
Kaposi's sarcoma
Halo nevus
Spitz nevus
Acral nevus
Connective tissue nevus