Hypermelanotic nevi must be differentiated from other types of pigmented skin lesions, including:

- Lentigo simplex

- Solar lentigo

- Café au lait macule

- Ink-spot lentigo

- Mucosal melanotic macule

- Mongolian spot (dermal melanocytosis)

The congenital melanocytic nevus appears as a circumscribed, light brown to black patch or plaque, potentially very heterogeneous in consistency, covering any size surface area and any part of the body.

As compared with a melanocytic nevus, congenital melanocytic nevi are usually larger in diameter and may have excess terminal hair, a condition called hypertrichosis. If over 40 cm projected adult diameter with hypertrichosis, it is sometimes called giant hairy nevus; more usually these largest forms are known as large or giant congenital melanocytic nevus. The estimated prevalence for the largest forms is 0.002% of births.

Melanocytic Nevi often grow proportionally to the body size as the child matures. As they mature, they often develop thickness, and become elevated, although these features can also be present from birth. Prominent terminal hairs often form, especially after puberty. With maturity, the nevus can have variation in color, and the surface might be textured with proliferative growths.

Neurocutaneous melanosis is associated with the presence of either giant congenital melanocytic nevi or non-giant nevi of the skin. It is estimated that neurocutaneous melanosis is present in 2% to 45% of patients with giant congenital melanocytic nevi. Neurocutaneous melanosis is characterized by the presence of congenital melanocytic nevi on the skin and melanocytic tumors in the leptomeninges of the central nervous system.

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.

Additional types of nevi do not involve disorders of pigmentation or melanocytes. These additional nevi represent hamartomatous proliferations of the epithelium, connective tissue, and vascular malformations.

Congenital melanocytic nevi may be divided into the following types:

- "Small-sized congenital melanocytic nevus" is defined as having a diameter less than 2 cm.

- "Medium-sized congenital melanocytic nevus" is defined as having a diameter more than 2 cm but less than 20 cm.

- "Giant congenital melanocytic nevus" (also known as "Bathing trunk nevus," "Garment nevus," "Giant hairy nevus", and "Nevus pigmentosus et pilosus") is defined by one or more large, darkly pigmented and sometimes hairy patches.

According to the American Academy of Dermatology, the most common types of moles are skin tags, raised moles and flat moles. Benign moles are usually brown, tan, pink or black (especially on dark-colored skin). They are circular or oval and are usually small (commonly between 1–3 mm), though some can be larger than the size of a typical pencil eraser (>5 mm). Some moles produce dark, coarse hair. Common mole hair removal procedures include plucking, cosmetic waxing, electrolysis, threading and cauterization.

Some sources equate the term mole with "melanocytic nevus". Other sources reserve the term "mole" for other purposes such as the animal of the same name.

Melanocytic nevi represent a family of lesions. The most common variants are:

- Location:

- Junctional nevus: the nevus cells are located along the junction of the epidermis and the underlying dermis. A junctional nevus is flat and brown to black.

- Compound nevus: a mixture of junctional and intradermal proliferation. Compound nevi are slightly raised and brown to black. Beauty marks are usually compound nevi of either the acquired variety or congenital variety.

- Intradermal nevus: the nevus cells are located in the dermis only. Intradermal nevi are raised; most are flesh-colored (not pigmented).

- Dysplastic nevus (nevus of Clark): 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 (atypical mole syndrome). According to the National Cancer Institute (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.

- Blue nevus: It is blue in color as its melanocytes are very deep in the skin. The nevus cells are spindle shaped and scattered in deep layers of the dermis. The covering epidermis is normal.

- Spitz nevus: a distinct variant of intradermal nevus, usually in a child. They are raised and reddish (non-pigmented). A pigmented variant, called the 'nevus of Reed', typically appears on the leg of young women.

- Acquired nevus: Any melanocytic nevus that is not a congenital nevus or not present at birth or near birth. This includes junctional, compound and intradermal nevus.

- 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.

- Giant pigmented nevus: these large, pigmented, often hairy congenital nevi. They are important because melanoma may occasionally (10 to 15%) appear in them.

- Intramucosal nevus: junctional nevus of the mucosa of the mouth or genital areas. In the mouth, they are found most frequently on the hard palate.

- Nevus of Ito and nevus of Ota: congenital, flat brownish lesions on the face or shoulder.

- 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.

- 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.

A seborrheic keratosis, also known as seborrheic verruca, basal cell papilloma, or a senile wart, is a non-cancerous (benign) skin tumour that originates from cells in the outer layer of the skin (keratinocytes). Like liver spots, seborrheic keratoses are seen more often as people age.

The tumours (also called lesions) appear in various colours, from light tan to black. They are round or oval, feel flat or slightly elevated, like the scab from a healing wound, and range in size from very small to more than across. They can often come in association with other skin conditions, including basal cell carcinoma. Sometimes seborrheic keratosis and basal cell carcinoma occur at the same location, and sometimes seborrheic keratosis progresses to basal cell carcinoma. At clinical examination the differential diagnosis include warts and melanoma. Because only the top layers of the epidermis are involved, seborrheic keratoses are often described as having a "pasted on" appearance. Some dermatologists refer to seborrheic keratoses as "seborrheic warts", because they resemble warts, but strictly speaking the term "warts" refers to lesions that are caused by human papillomavirus.

Often, this disease evolves from a precursor lesion, usually a dysplastic nevus. Otherwise it arises in previously normal skin. A prolonged radial growth phase, where the lesion remains thin, may eventually be followed by a vertical growth phase where the lesion becomes thick and nodular. As the risk of spread varies with the thickness, early SSM is more frequently cured than late nodular melanoma.

The microscopic hallmarks are:

- Large melanocytic cells with nest formation along the dermo-epidermal junction.

- Invasion of the upper epidermis in a pagetoid fashion (discohesive single cell growth).

- The pattern of rete ridges is often effaced.

- Invasion of the dermis by atypical, pleomorphic melanocytes

- Absence of the 'maturation' typical of naevus cells

- Mitoses

The melanocytes left behind in the wound regrow in an abnormal pattern. Rather than the even and regular lace like network, the pigments tends to grow in streaks of varying width within the scar. This is often accompanied by scarring, inflammation, and blood vessel changes – giving both the clinical and histologic impression of a melanoma or a severe dysplastic nevus. When the patient is reexamined years later without the assistance of the original biopsy report, the physician will often require the removal of the scar with the recurrent nevus to assure that a melanoma is not missed.

Nevus sebaceus or sebaceous nevus (the first term is its Latin name, the second term is its name in English; also known as an "organoid nevus" and "nevus sebaceus of Jadassohn") is a congenital, hairless plaque that typically occurs on the face or scalp. Such nevi are present at birth, or early childhood, affecting males and females of all races equally. The condition is named for an overgrowth of sebaceous glands in the area of the nevus.

Skin growths such as benign tumors and basal cell carcinoma can arise in sebaceous nevi, usually in adulthood. Rarely, sebaceous nevi can give rise to sebaceous carcinoma. However, the rate of such malignancies is now known to be less than had been estimated. For this reason, excision is no longer automatically recommended.

The most common location by far is the gingival margin and other areas of the masticatory oral mucosa, these occur more frequently in the fifth decade of life, and have good prognosis, the treatment of choice for oral VXs is surgical excision, and recurrence is rare.

The condition can affect other organs of body, such as the penis, vulva, and can occur in anal region, nose, the ear, lower extremity, scrotum.

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.

Seborrheic keratoses may be divided into the following types:

- Common seborrheic keratosis (basal cell papilloma, solid seborrheic keratosis)

- Reticulated seborrheic keratosis (adenoid seborrheic keratosis)

- Stucco keratosis (digitate seborrheic keratosis, hyperkeratotic seborrheic keratosis, serrated seborrheic keratosis, verrucous seborrheic keratosis) -- Often are light brown to off-white. Pinpoint to a few millimeters in size. Often found on the distal tibia, ankle, and foot.

- Clonal seborrheic keratosis

- Irritated seborrheic keratosis (inflamed seborrheic keratosis)

- Seborrheic keratosis with squamous atypia

- Melanoacanthoma (pigmented seborrheic keratosis)

- Dermatosis papulosa nigra—Commonly found among adult dark-skinned individuals, presents on the face as small benign papules from a pinpoint to a few millimeters in size.

- Inverted follicular keratosis

Also see:

- The sign of Leser-Trélat

Pseudomelanoma (also known as a "recurrent melanocytic nevus", and "recurrent nevus") is a cutaneous condition in which melantic skin lesions clinically resemble a superficial spreading melanoma at the site of a recent shave removal of a melanocytic nevus.

Differential diagnosis includes seborrheic keratosis, verruca simplex, condyloma acuminatum, granular cell myoblastoma, vulvar intraepithelial neoplasia, bowenoid papulosis, erythroplasia of Queyrat, and verrucous carcinoma

Superficial spreading melanoma (also known as "superficially spreading melanoma") (SSM) is usually characterized as the most common form of cutaneous melanoma in Caucasians. The average age at diagnosis is in the fifth decade, and it tends to occur on sun-exposed skin, especially on the backs of males and lower limbs of females.

Melanoma with features of a Spitz nevus (also known as a "Spitzoid melanoma") is a cutaneous condition characterized histologically with tissue similar to a spitz nevus and with overall symmetry and a dermal nodule of epithelioid melanocytes that do not mature with progressively deeper dermal extension.

Nevoid melanoma is a cutaneous condition that may resemble a Spitz nevus or an acquired or congenital melanocytic nevus.

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.

Characteristics include a blue/black stain of skin initially. Skin is thin, about 4-5 cell layers thick, which is often related to aging. Histological features include epidermal atrophy and increased number of melanocytes.

Epithelioma cuniculatum (also known as Carcinoma cuniculatum, and Ackerman tumor) is a skin lesion, a type of verrucous carcinoma that may occur on the sole of the foot.

A Spitz nevus (also known as an epithelioid and spindle-cell nevus, benign juvenile melanoma, and "Spitz's juvenile melanoma") is a benign melanocytic nevus, a type of skin lesion, affecting the epidermis and dermis.

The name "juvenile melanoma" is generally no longer used as it is misleading: it is not a melanoma, it is a benign lesion; and it can also occur in adults, not only in children.

Bowenoid papulosis is a cutaneous condition characterized by the presence of pigmented verrucous papules on the body of the penis. They are associated with human papillomavirus, the causative agent of genital warts. The lesions have a typical dysplastic histology and are generally considered benign, although a small percentage will develop malignant characteristics.

It is considered as a pre-malignant condition. Other terms used to describe the condition are: Erythroplasia of Queyrat, Squamous cell carcinoma in situ and Bowen’s disease. The term "Bowenoid papulosis" was coined in 1977 by Kopf and Bart and is named after dermatologist John Templeton Bowen.

The term “intraepithelial neoplasia” defines a premalignant intraepithelial change.

On the vulva it is termed VIN (vulvar or vulval intraepithelial neoplasia); on the penis, PIN (penile intraepithelial neoplasia); and on or around the anus, AIN (anal intraepithelial neoplasia). The terminology has been very confusing and it is now recommended that the terms Bowen’s disease, erythroplasia of Queyrat, and bowenoid papulosis should not be used for lesions in the anogenital area. However, dermatologists still recognize a distinct clinical variant, bowenoid papulosis, characterized by discrete papules in a younger age group and a tendency for spontaneous regression. Additionally, some authorities believe that erythroplasia of Queyrat and Bowen’s disease remain useful terms in men.

Phakomatosis pigmentovascularis is subdivided into five types:

- Type 1 PWS + epidermal nevus

- Type 2 (most common): PWS + dermal melanocytosis +/- nevus anemicus

- Type 3: PWS + nevus spilus +/- nevus anemicus

- Type 4: PWS + nevus spilus + dermal melanocytosis +/- nevus anemicus

- Type 5: CMTC (Cutis marmorata telangiectatica congenita) + dermal melanocytosis

They all can contain capillary malformation. Type 2 is the most common and can be associated with granular cell tumor. Some further subdivide each type into categories A & B; with A representing oculocutaneous involvement and subtype B representing extra oculocutaneous involvement. Others have proposed fewer subtypes but currently this rare entity is mostly taught as having five subtypes currently.