Mucinous nevus (also known as "Nevus mucinosus") is a rare cutaneous condition characterized by hamartoma that can be congenital or acquired.

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.

The term "nevus" is applied to a number of conditions caused by neoplasias and hyperplasias of melanocytes, as well as a number of pigmentation disorders, both hypermelanotic (containing increased melanin, the pigment responsible for skin color) and hypomelanotic (containing decreased melanin).

A basaloid follicular hamartoma is a cutaneous condition characterized as distinctive benign adnexal tumor that has several described variants.

A folliculosebaceous-apocrine hamartoma, also known as "follicular-apocrine hamartoma", is a benign proliferation of the folliculosebaceous-apocrine unit.

Since the original identification of Schimmelpenning syndrome, the number of findings has expanded to the point that the syndrome is associated with a considerable constellation of abnormalities. The abnormalities may occur in a variety of combinations, and need not include all three aspects of the classic triad of sebaceous nevus, seizures and mental retardation. In 1998, a literature review by van de Warrenburg et al. found:

- seizures in 67% of cases

- mental retardation in 61% of cases

- ophthalmological abnormalities in 59% of cases

- involvement of other organ systems in 61% of cases

- structural abnormality of cerebrum or cranium in 72% of cases

The major neurological abnormalities include mental retardation to varying extent, seizures, and hemiparesis. Seizures, when present, typically begin during the first year of life. The most common structural central nervous system abnormalities in Schimmelpenning syndrome are hemimegalencephaly and ipselateral gyral malformations.

The major ocular abnormalities are colobomas and choristomas.

Skeletal abnormalities may include dental irregularities, scoliosis, vitamin D-resistant rickets and hypophosphatemia. Cardiovascular abnormalities include ventricular septal defect and co-arctation of the aorta; urinary system issues include horseshoe kidney and duplicated urinary collection 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.

People with Cowden syndrome develop characteristic lesions called hamartomas, which are small, noncancerous growths that are most commonly found on the skin and mucous membranes (such as the lining of the mouth, nose, and intestines), but can also occur other parts of the body, such as the thyroid and breast. The majority of affected individuals develop the characteristic skin lesions by 20 years of age.

Hamartomas are typically benign; however, people with Cowden syndrome are at increased risk of developing several types of cancer, including cancers of the breast, thyroid, uterus (endometrial), and kidney cancers. Two thirds of people have thyroid abnormalities, which usually consist of follicular adenomas (benign) or multinodular goiter of the thyroid. Up to 10 percent of people with Cowden Syndrome develop follicular thyroid cancer.

Skin abnormalities in people with Cowdens syndrome can include oral and skin papillomas and benign growths of the skin called trichilemmomas. Additional signs and symptoms of Cowden syndrome can include an enlarged head (macrocephaly), a rare noncancerous brain tumor called Lhermitte-Duclos disease, and glycogenic acanthosis of the esophagus. Up to 75% have benign breast conditions such as ductal hyperplasia, intraductal papillomatosis, adenosis, lobular atrophy, fibroadenomas, and fibrocystic changes.

Bannayan–Riley–Ruvalcaba syndrome is associated with enlarged head and benign mesodermal hamartomas (multiple hemangiomas, and intestinal polyps). Dysmorphy as well as delayed neuropsychomotor development can also be present. The head enlargement does not cause widening of the ventricles or raised intracranial pressure; these individuals have a higher risk of developing tumors, as the gene involved in BRRs is phosphatase and tensin homologue.

Some individuals have thyroid issues consistent with multinodular goiter, thyroid adenoma, differentiated non-medullary thyroid cancer,

most lesions are slowly growing. Visceral as well as intracranial involvement may occur in some cases, and can cause bleeding and symptomatic mechanical compression

Eccrine angiomatous hamartoma usually appear as a solitary nodular lesion on the acral areas of the extremities, particularly the palms and soles.

Folliculosebaceous cystic hamartoma abbreviated as (FSCH) is a rare cutaneous hamartoma consisting of dilated folliculosebaceous units invested in mesenchymal elements. it typically affects adults, have a predilection for the central face or scalp, with less than 1.5 cm dimension. Clinically, the lesions are asymptomatic, rubbery to firm in consistency, and usually occur on or above the neck in (> 90%) of cases, Histopathologically, FSCH shares several similar features to sebaceous trichofolliculoma, but it is usually possible to differentiate these two tumors.

This condition is characterised by symmetrical lesions on the temples resembling forceps marks. It is characterized a puckered skin due to a virtual absence of subcutaneous fat. It is apparent at birth. Other lesions that may be present include puffy, wrinkled skin around the eyes and/or abnormalities of the eyelashes, eyebrows, and eyelids. The eyebrows may be up slanting or outward slanting. Occasionally the bridge of the nose may appear flat, while the tip may appear unusually rounded. The chin may be furrowed. The upper lip may be prominent with a down turned mouth. Other features that have been reported include dysplastic and low set ears, linear radiatory impressions on the forehead and congenital horizontal nystagmus.

Those with the Setleis syndrome may be missing eyelashes on both the upper and lower lids or may have multiple rows of lashes on the upper lids but none on the lower lids.A possible association with intra abdominal cancer has been reported but to date this has not been confirmed in other studies.

Syringomas are harmless eccrine sweat duct tumors, typically found clustered on eyelids, although they may also be found in the armpits, abdomen, chest, neck, scalp or groin area including genitals in a symmetric pattern. They are skin-colored or yellowish firm, rounded bumps, 1–3 mm in diameter, and may be confused with xanthoma, milia, hidrocystoma, trichoepithelioma, and xanthelasma. They are more common in women and are most commonly found in middle-aged Asian women. While they can present at any time in life, they typically present during adolescence. They are usually not associated with any other symptoms although can sometimes cause itchiness or irritation.

Schimmelpenning syndrome is a neurocutaneous condition characterized by one or more sebaceous nevi, usually appearing on the face or scalp, associated with anomalies of the central nervous system, ocular system, skeletal system, cardiovascular system, and genitourinary system.

Synonyms include: "Linear nevus sebaceous syndrome (LNSS)", "Schimmelpenning-Feuerstein-Mims syndrome", "Feuerstein-Mims syndrome", "sebaceous nevus syndrome", "Solomon syndrome", and "Jadassohn's nevus phakomatosis". "Nevus" is sometimes spelled "naevus" and "sebaceous" may also be spelled "sebaceus". "Epidermal nevus syndrome" is sometimes used as a synonym, but more often as a broader term referring to Schimmelpenning syndrome in addition to nevus comedonicus syndrome, CHILD syndrome, Becker's nevus syndrome, and phakomatosis pigmentokeratotica.

The classic Schimmelpenning syndrome diagnosis comprises a triad of sebaceous nevi, seizures, and mental retardation. The condition was first reported by Gustav Schimmelpenning in 1957 and independently reported by Feuerstein and Mims in 1962.

Hair follicle nevus (also known as a "Vellus hamartoma") is a cutaneous condition that presents as a small papule from which fine hairs protrude evenly from the surface.

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.

Cowden syndrome (also known as Cowden's disease and sometimes as multiple hamartoma syndrome) is a rare autosomal dominant inherited disorder characterized by multiple non-cancerous tumor-like growths called hamartomas, which typically are found in the skin, mucous membranes (mouth, nasal membranes, GI tract), thyroid gland, and breast tissue. While the hamartomas are benign, people with Cowden syndrome are at increased risk of certain forms of cancer, including breast, thyroid, uterus (endometrial), and kidney cancers.

Cowden syndrome is associated with mutations in PTEN, a tumor suppressor gene, that cause the PTEN protein not to work properly leading to hyperactivity of the mTOR pathway. These mutations lead to characteristic features including macrocephaly, intestinal hamartomatous polyps, benign skin tumors (multiple trichilemmomas, papillomatous papules, and acral keratoses) and dysplastic gangliocytoma of the cerebellum (Lhermitte-Duclos disease). In addition, there is a predisposition to breast carcinoma, follicular carcinoma of the thyroid, and endometrial carcinoma.

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 lentigo () (plural lentigines, ) is a small pigmented spot on the skin with a clearly defined edge, surrounded by normal-appearing skin. It is a harmless (benign) hyperplasia of melanocytes which is linear in its spread. This means the hyperplasia of melanocytes is restricted to the cell layer directly above the basement membrane of the epidermis where melanocytes normally reside. This is in contrast to the "nests" of multi-layer melanocytes found in moles (melanocytic nevi). Because of this characteristic feature, the adjective "lentiginous" is used to describe other skin lesions that similarly proliferate linearly within the basal cell layer.

Lentigines are distinguished from freckles (ephelis) based on the proliferation of melanocytes. Freckles have a relatively normal number of melanocytes but an increased "amount" of melanin. A lentigo has an increased "number" of melanocytes. Freckles will increase in number and darkness with sunlight exposure, whereas lentigines will stay stable in their color regardless of sunlight exposure.

Lentigines by themselves are benign, however one might desire the removal or treatment of some of them for cosmetic purposes. In this case they can be removed surgically, or lightened with the use of topical depigmentation agents. Some common depigmentation agents such as azelaic acid and kojic acid seem to be inefficient in this case, however other agents might work well (4% hydroquinone, 5% topical cysteamine, 10% topical ascorbic acid).

Conditions characterized by lentigines include:

- Lentigo simplex

- Solar lentigo (Liver spots)

- PUVA lentigines

- Ink spot lentigo

- LEOPARD syndrome

- Mucosal lentigines

- Multiple lentigines syndrome

- Moynahan syndrome

- Generalized lentiginosis

- Centrofacial lentiginosis

- Carney complex

- Inherited patterned lentiginosis in black persons

- Partial unilateral lentiginosis

- Peutz-Jeghers syndrome

- Lentigo maligna

- Lentigo maligna melanoma

- Acral lentiginous melanoma

Focal dermal hypoplasia (also known as "Goltz syndrome") is a form of ectodermal dysplasia. It is a multisystem disorder characterized primarily by skin manifestations to the atrophic and hypoplastic areas of skin which are present at birth. These defects manifest as yellow-pink bumps on the skin and pigmentation changes. The disorder is also associated with shortness of stature and some evidence suggests that it can cause epilepsy.

Focal facial dermal dysplasia (FFDD) is a rare genetically heterogeneous group of disorders that are characterized by congenital bilateral scar like facial lesions, with or without associated facial anomalies. It is characterized by hairless lesions with fingerprint like puckering of the skin, especially at the temples, due to alternating bands of dermal and epidermal atrophy.

This condition is also known as Brauer syndrome (hereditary symmetrical aplastic nevi of temples, bitemporal aplasia cutis congenita, bitemporal aplasia cutis congenita: OMIM ) and Setleis syndrome (facial ectodermal dysplasia: OMIM ).

Congenital smooth muscle hamartoma is typically a skin colored or lightly pigmented patch or plaque with hypertrichosis.

Local gigantism or localised gigantism is a condition in which a certain part of the body acquires larger than normal size due to excessive growth of the anatomical structures or abnormal accumulation of substances. It is more common in fingers and toes, where it is termed macrodactyly. However, sometimes an entire limb may be enlarged.

Fibrous hamartoma of infancy is a rapidly growing, painless, ill-defined subcutaneous or intradermal nodule that is generally solitary and less than 5 cm in size, though, rarely, multiple lesions occur synchronously.

By 1999, there were 12 reported cases.

The majority of patients are less than 2 years old, with 25% of cases being congenital. Possible locations include the trunk and limbs; usually the upper arm or shoulder. Local excision is the treatment of choice, but it may recur locally.

Local gigantism may be caused by a heterogeneous group of both congenital and acquired conditions.