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:

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.

As halo nevi are only of cosmetic significance, no treatment is required, and patients will be asymptomatic. Although halo nevi are harmless, it is important to monitor the lesion on regular basis. Watch out for any changes in appearance of existing or new halo nevi. If there is any change in appearance or is associated with pain, itch, and infection, a doctor should be consulted immediately to exclude the possibility of melanoma.

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

Some patients have a few or no histopathologic abnormalities. Histological examination of a biopsy may show an increase in the number and size of capillaries and veins (rarely lymphatics), dilated capillaries located in the deeper dermis, and hyperplasia and swollen endothelial cells with occasional dilated veins and venous lakes.

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%).

Screening for melanoma in FAMMM kindreds should begin at age 10 with a baseline total body skin examination including scalp, eyes, oral mucosa, genital area, and nail, as family members may develop melanoma in their early teens.

At Mayo Clinic, FAMMM patients with a confirmed mutation and family history of pancreatic cancer are offered screening with either high-resolution pancreatic protocol CT, MRI, or endoscopic ultrasound starting at age 50 or 10 years younger than the earliest family member with pancreas cancer. They are counseled on the lack of evidence-based data to support screening, and on the limitations of our current technology to detect a lesion at a stage amenable to therapy.

Halo nevi are estimated to be present in approximately 1% of the general population, and are found to be more prevalent in people with vitiligo, malignant melanoma, or Turner syndrome. All races and sexes are equally susceptible to this disease, although a familial tendency has been reported. The average age of onset is in a person's teenage years.

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.

Differential diagnosis of this condition includes the Birt-Hogg-Dubé syndrome and tuberous sclerosis. As the skin lesions are typically painful, it is also often necessary to exclude other painful tumors of the skin (including blue rubber bleb nevus, leiomyoma, eccrine spiradenoma, neuroma, dermatofibroma, angiolipoma, neurilemmoma, endometrioma, glomus tumor and granular cell tumor; the mnemonic "BLEND-AN-EGG" may be helpful). Other skin lesions that may need to be considered include cylindroma, lipoma, poroma and trichoepithelioma; these tend to be painless and have other useful distinguishing features.

In general, children with a small isolated nevus and a normal physical exam do not need further testing; treatment may include potential surgical removal of the nevus. If syndrome issues are suspected, neurological, ocular, and skeletal exams are important. Laboratory investigations may include serum and urine calcium and phosphate, and possibly liver and renal function tests. The choice of imaging studies depends on the suspected abnormalities and might include skeletal survey, CT scan of the head, MRI, and/or EEG.

Depending on the systems involved, an individual with Schimmelpenning syndrome may need to see an interdisciplinary team of specialists: dermatologist, neurologist, ophthalmologist, orthopedic surgeon, oral surgeon, plastic surgeon, psychologist.

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.

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.

The skin lesions may be difficult to diagnose clinically but a punch biopsy will usually reveal a Grenz zone separating the tumour from the overlying skin. Histological examination shows dense dermal nodules composed of elongated cells with abundant eosinophilic cytoplasm arranged in fascicles (spindle cells). The nuclei are uniform, blunt-ended and cigar-shaped with only occasional mitoses. Special stains that may be of use in the diagnosis include Masson's trichrome, Van Gieson's stain and phosphotungstic acid–haematoxylin.

The renal cell carcinomas have prominent eosinophilic nucleoli surrounded by a clear halo.

Spitz nevi are uncommon. Their annual incidence was estimated in a coastal population of sub-tropical Queensland to be 1.4 cases per 100,000 people. For comparison, the annual incidence of melanoma in the same population, which is high by world standards is 25.4 cases per 100,000 people.

Although they are most commonly found on people in their first two decades of life, the age range for people with Spitz nevi is from 6 months to 71 years, with a mean age of 22 years and a median age of 19 years.

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.

Nevus comedonicus (also known as a "comedo nevus") is characterized by closely arranged, grouped, often linear, slightly elevated papules that have at their center keratinous plugs resembling comedones.

A Q-switched laser has been successfully used to treat the condition.

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.

As Becker's nevus is considered a benign lesion, treatment is generally not necessary except for cosmetic purposes. Shaving or trimming can be effective in removing unwanted hair, while electrology or laser hair removal may offer a longer-lasting solution. Different types of laser treatments may also be effective in elimination or reduction of hyperpigmentation, though the results of laser treatments for both hair and pigment reduction appear to be highly variable.

Xanthoma disseminatum (also known as "Disseminated xanthosiderohistiocytosis" and "Montgomery syndrome") is a rare cutaneous condition that preferentially affects males in childhood, characterized by the insidious onset of small, yellow-red to brown papules and nodules that are discrete and disseminated.

It is a histiocytosis syndrome.

Phakomatosis pigmentokeratotica is a rare neurocutanous condition characterized by the combination of an organoid sebaceous nevus and speckled lentiginous nevus. It is an unusual variant of epidermal naevus syndrome. It was first described by Happle "et al". It is often associated with neurological or skeletal anomalies such as hemiatrophy, dysaesthesia and hyperhidrosis in a segmental pattern, mild mental retardation, seizures, deafness, ptosis and strabismus.

Phakomatosis pigmentovascularis is a rare neurocutanous condition where there is coexistence of a capillary malformation (port-wine stain) with various melanocytic lesions, including dermal melanocytosis (Mongolian spots), nevus spilus, and nevus of Ota.

Nevus of Ito (also known as "Nevus fuscoceruleus acromiodeltoideus") is a skin condition with similar features to the Nevus of Ota, but occurring in a different distribution.