Nevi are typically diagnosed clinically with the naked eye or using dermatoscopy. More advanced imaging tests are available for distinguishing melanocytic nevi from melanoma, including computerized dermoscopy and image analysis. The management of nevi depends on the type of nevus and the degree of diagnostic uncertainty. Some nevi are known to be benign, and may simply be monitored over time. Others may warrant more thorough examination and biopsy for histopathological examination (looking at a sample of skin under a microscope to detect unique cellular features). For example, a clinician may want to determine whether a pigmented nevus is a type of melanocytic nevus, dysplastic nevus, or melanoma as some of these skin lesions pose a risk for malignancy. The ABCDE criteria (asymmetry, border irregularity, color variegation, diameter > 6 mm, and evolution) are often used to distinguish nevi from melanomas in adults, while modified criteria (amelanosis, bleeding or bumps, uniform color, small diameter or de novo, and evolution) can be used when evaluating suspicious lesions in children. In addition to histopathological examination, some lesions may also warrant additional tests to aid in diagnosis, including special stains, immunohistochemistry, and electron microscopy. Typically; the nevi which exist since childhood are harmless

The management of a nevus depends on the specific diagnosis, however, the options for treatment generally include the following modalities:

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.

Visual diagnosis is made by the "stuck on" appearance, horny pearls or cysts embedded in the structure. Darkly pigmented lesions can be challenging to distinguish from nodular melanomas. Furthermore, thin seborrheic keratoses on facial skin can be very difficult to differentiate from lentigo maligna even with dermatoscopy. Clinically, epidermal nevi are similar to seborrheic keratoses in appearance. Epidermal nevi are usually present at or near birth. Condylomas and warts can clinically resemble seborrheic keratoses, and dermatoscopy can be helpful. On the penis and genital skin, condylomas and seborrheic keratoses can be difficult to differentiate, even on biopsy.

To date, the gold standard in the diagnosis of seborrheic keratosis is represented by the histolopathologic analysis of a skin biopsy.

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 mnemonic 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.

Large and especially giant congenital nevi are at higher risk for malignancy degeneration into melanoma. Because of the premalignant potential, it is an acceptable clinical practice to remove congenital nevi electively in all patients and relieve the nevocytic overload.

No treatment of seborrheic keratoses is necessary, except for aesthetic reasons. Since a slightly increased risk of localized infection caused by picking at the lesion has been described, if a lesion becomes itchy or irritated by clothing or jewelry, a surgical excision is generally recommended.

Small lesions can be treated with light electrocautery. Larger lesions can be treated with electrodesiccation and curettage, shave excision, or cryosurgery. When correctly performed, removal of seborrheic keratoses will not cause much visible scarring except in persons with dark skin tones.

Benign congenital nevi can have histological characteristics resembling melanomas, often breaking most if not all of the ABCDE rules. Dermatoscopic findings of the smaller forms of benign congenital nevi can aid in their differentiation from other pigmented neoplasms.

Microscopically, congenital melanocytic nevi appear similar to acquired nevi with two notable exceptions. For the congenital nevus, the neval cells are found deeper into the dermis. Also, the deeper nevus cells can be found along with neurovascular bundles, with both surrounding hair follicles, sebaceous glands, and subcutaneous fat. Such annexes and the hypodermis can also be hypoplasic or, conversely, present aspects of hamartoma.

Treatment is by excisional biopsy, wide local excision and possibly sentinel node biopsy. Spread of disease to local lymph nodes or distant sites (typically brain, bone, skin and lung) marks a decidedly poor prognosis.

Due to the rarity of different types of vascular conditions, angiokeratomas may be misdiagnosed. A biopsy of the lesion can produce a more accurate diagnosis.

First dilemma in diagnosis is recognition. As lentigo malignas often present on severely sun-damaged skin, it is frequently found amongst numerous pigmented lesions – thin seborrheic keratoses, lentigo senilis, lentigines. It is difficult to distinguish these lesions with the naked eye alone, and even with some difficulty using dermatoscopy. As the lentigo maligna is often very large, it often merges with, or encompasses other skin tumors – such as lentigines, melanocytic nevi, and seborrheic keratosis.

Second dilemma is the biopsy technique. Even though excisional biopsy (removing the entire lesion) is ideal, and advocated by pathologists; practical reason dictates that this should not be done. These tumors are often large and presenting on the facial area. Excision of such large tumor would be absolutely contraindicated if the lesion's identity is uncertain. The preferred method of diagnosis is by using a punch biopsy, allowing the physician to sample multiple full thickness pieces of the tumor at multiple sites. While one section of the tumor might show benign melanocytic nevus, another section might show features concerning for severe cellular atypia. When cellular atypia is noted, a pathologist might indicate that the entire lesion should be removed. It is at this point that one can comfortablly remove the entire lesion, and thus confirm the final diagnosis of lentigo maligna. The size of the punch biopsy can vary from 1 mm to 2 mm, but it is preferable to use a punch 1.5 mm or larger. Representative samples of the most atypical parts of the nevus should be biopsied, often guided by dermatoscopy.

Since the histopathology of nevus anemicus is normal, nevus anemicus is a pharmacologic nevus and not an anatomic one. In most people a nevus anemicus is on a covered area and so light in appearance that no treatment is needed.

Also known as "scoop", "scallop", or "shave" excisional biopsy, or "shave excision". A trend has occurred in dermatology over the last 10 years with the advocacy of a deep shave excision of a pigmented lesion An author published the result of this method and advocated it as better than standard excision and less time consuming. The added economic benefit is that many surgeons bill the procedure as an excision, rather than a shave biopsy. This save the added time for hemostasis, instruments, and suture cost. The great disadvantage, seen years later is the numerous scallop scars, and a very difficult to deal with lesions called a "recurrent melanocytic nevus". What has happened is that many "shave" excisions does not adequately penetrate the dermis or subcutanous fat enough to include the entire melanocytic lesion. Residual melanocytes regrow into the scar. The combination of scarring, inflammation, blood vessels, and atypical pigmented streaks seen in these recurrent nevus gives the perfect dermatoscopic picture of a melanoma. When a second physicians re-examine the patient, he or she has no choice but to recommend the reexcision of the scar. If one does not have access to the original pathology report, it is impossible to tell a recurring nevus from a severely dysplastic nevus or a melanoma. As the procedure is widely practiced, it is not unusual to see a patient with dozens of scallop scars, with as many as 20% of the scars showing residual pigmentation. The second issue with the shave excision is fat herniation, iatrogenic anetoderma, and hypertrophic scarring. As the deep shave excision either completely remove the full thickness of the dermis or greatly diminishing the dermal thickness, subcutanous fat can herniate outward or pucker the skin out in an unattractive way. In areas prone to friction, this can result in pain, itching, or hypertrophic scarring.

A healthcare provider can usually diagnose a port-wine stain based entirely upon the history and appearance. In unusual cases, a skin biopsy may be needed to confirm the diagnosis. Depending on the location of the birthmark and other associated symptoms, a physician may choose to order a measurement of intraocular pressure or X-ray of the skull.

A MRI scan of the brain may be performed (under anesthesia) on infants who have a port-wine stain in the head area in order to check for signs of Sturge-Weber syndrome.

If the port-wine stain is inside the mouth, a provider may check the insides of a newborn baby's throat with a scope to see if there are any changes (growths) other than just the color.

If the port-wine stain is around the eye or on the eyelid, a referral may be made to an optometrist or ophthalmologist for a test of the ocular pressures in that eye. If swelling occurs in the port-wine stain, it may cause vision problems, glaucoma, or blindness.

Angiokeratoma may be classified as:

- "Angiokeratoma of Mibelli" (also known as "Mibelli's angiokeratoma," "Telangiectatic warts") consists of 1- to 5-mm red vascular papules, the surfaces of which become hyperkeratotic in the course of time. The disease is named after Italian dermatologist Vittorio Mibelli (1860-1910).

- "Angiokeratoma of Fordyce" (also known as "Angiokeratoma of the scrotum and vulva," though not to be confused with Fordyce's spots) is a skin condition characterized by red to blue papules on the scrotum or vulva.

- "Solitary angiokeratoma" is a small, bluish-black, warty papule that occurs predominantly on the lower extremities.

- "Verrucous vascular malformation" (also known as "Angiokeratoma circumscriptum naeviforme") is a malformation of dermal and subcutaneous capillaries and veins, a congenital vascular malformation, which, over time, a verrucous component appears.

Usually observed at birth or shortly thereafter in 94% of patients, in other reports, patients did not develop skin lesions until 3 months or even 2 years after birth. Females are typically affected more often than males (64%).

Blue nevi may be divided into the following types:

- A "patch blue nevus" (also known as an "acquired dermal melanocytosis", and "dermal melanocyte hamartoma") is a cutaneous condition characterized by a diffusely gray-blue area that may have superimposed darker macules.

- A "blue nevus of Jadassohn–Tièche" (also known as a "common blue nevus", and "nevus ceruleus") is a cutaneous condition characterized by a steel-blue papule or nodule.

- A "cellular blue nevus" is a cutaneous condition characterized by large, firm, blue or blue-black nodules.

- An "epithelioid blue nevus" is a cutaneous condition most commonly seen in patients with the Carney complex.

- A "deep penetrating nevus" is a type of benign melanocytic skin tumor characterized, as its name suggests, by penetration into the deep dermis and/or subcutis. Smudged chromatic is a typical finding. In some cases mitotic figures or atypical melanocytic cytology are seen, potentially mimicking a malignant melanoma. Evaluation by an expert skin pathologist is advisable in some cases to help differentiate from invasive melanoma.

- An "amelanotic blue nevus" (also known as a "hypomelanotic blue nevus") is a cutaneous condition characterized by mild atypia and pleomorphism.

- A "malignant blue nevus" is a cutaneous condition characterized by a sheet-like growth pattern, mitoses, necrosis, and cellular atypia.

There is no treatment, but because this is a benign condition with no serious clinical complications, prognosis is excellent.

In the absence of successful treatment, hypertrophy (increased tissue mass) of the stains may cause problems later in life, such as loss of function (especially if the stain is near the eye or mouth), bleeding, and increasing disfigurement. Lesions on or near the eyelid can be associated with glaucoma. If the port-wine stain is on the face or other highly visible part of the body, its presence can also cause emotional and social problems for the affected person.

It is suggested that gene therapy might be used as a cure in the future.

Linear verrucous epidermal nevus (also known as a "Linear epidermal nevus," and "Verrucous epidermal nevus") is a skin lesion characterized by a verrucous skin-colored, dirty-gray or brown papule. Generally, multiple papules present simultaneously, and coalesce to form a serpiginous plaque. When this nevus covers a diffuse or extensive portion of the body's surface area, it may be referred to as a systematized epidermal nevus, when it involved only one-half of the body it is called a nevus unius lateris.

Blue nevus (also known as "blue neuronevus", "dermal melanocytoma", and "nevus bleu") is a type of melanocytic nevus. The blue colour is caused by the pigment being deeper in the skin than in ordinary nevi. In principle they are harmless but they can sometimes be mimicked by malignant lesions, i.e. some melanomas can look like a blue nevus.

These are localized white spots on skin which may affect any area of the body, but these white spots are quite stable lesions. In the majority of patients, the lesions are not completely achromic, but are hypopigmented and resemble splashed paint. The individual lesions are permanent and there are no effective therapies for re-pigmenting this nevus. If there is hair in an affected area, it is usually colourless or white.

Verruciform xanthoma is uncommon, with a female:male ratio of 1:1.1

Diagnosis is based on visual examination and the presence of itching. A skin biopsy is often performed to exclude other diseases. Lesion biopsies will typically show a high level of eosinophils in PN. A culture of at least one lesion will rule out staphylococcus infection, which has been significantly linked to atopic dermatitis.

The physical examination of the skin and its appendages, as well as the mucous membranes, forms the cornerstone of an accurate diagnosis of cutaneous conditions. Most of these conditions present with cutaneous surface changes termed "lesions," which have more or less distinct characteristics. Often proper examination will lead the physician to obtain appropriate historical information and/or laboratory tests that are able to confirm the diagnosis. Upon examination, the important clinical observations are the (1) morphology, (2) configuration, and (3) distribution of the lesion(s). With regard to morphology, the initial lesion that characterizes a condition is known as the "primary lesion," and identification of such a lesions is the most important aspect of the cutaneous examination. Over time, these primary lesions may continue to develop or be modified by regression or trauma, producing "secondary lesions." However, with that being stated, the lack of standardization of basic dermatologic terminology has been one of the principal barriers to successful communication among physicians in describing cutaneous findings. Nevertheless, there are some commonly accepted terms used to describe the macroscopic morphology, configuration, and distribution of skin lesions, which are listed below.