Benign skin tumours and naevi

• Benign tumours and naevi are the lumps, bumps and moles clinicians see every day: seborrhoeic keratosis, melanocytic (pigmented) naevi, atypical (dysplastic) naevi, dermatofibroma, lipoma, epidermoid cyst, haemangioma, pyogenic granuloma and skin tag.
• Most are diagnosed on inspection and dermoscopy, and most need no treatment at all. Removing them can leave a scar that is uglier than the lesion.
• The job is not to remove everything but to recognise the one lesion that is malignant, to confirm what a suspicious lesion is, and to remove the benign lesion for a clear reason.
• Dermoscopy is the single most useful bedside test: it is more sensitive and specific than naked-eye examination and is expected when any pigmented lesion is specialist-assessed.
• A pigmented lesion that meets the NICE weighted seven-point checklist threshold of 3 or more, or that looks melanocytic under the dermatoscope, goes on a suspected cancer pathway rather than being treated as a benign lesion. ^[12]

By the end of this page you should be able to:

1. Recognise the common benign skin tumours and naevi by their typical history and appearance.
2. Use dermoscopy to support the diagnosis of seborrhoeic keratosis, melanocytic naevi, dermatofibroma and vascular lesions.
3. Decide when a lesion can be left alone, when it should be sampled, and when it must be referred on a suspected cancer pathway.
4. Describe the management (including typical techniques and, where supported, doses) of the lesions covered.
5. Recognise atypical naevus syndrome and familial atypical multiple mole melanoma (FAMMM) syndrome and know who needs surveillance.
6. Adapt recognition and management to a setting where dermatoscopy, histology or surgery is unavailable.

"Benign" on the skin means the lesion is a local, non-invasive proliferation: it does not spread and usually needs no treatment. The difficult part is that benign lesions can look like melanoma, basal cell carcinoma or squamous cell carcinoma, and early melanoma can look like an innocent mole. The whole page is built around that one decision: watch, sample, or refer.

The lesions below are grouped by what the patient sees (colour and shape) rather than by strict histology, because that is how they are met in the clinic.

A seborrhoeic keratosis is a prevalent benign skin condition made of immature epidermal keratinocytes. It looks like a brown to black, scaly papule or plaque that is firmly "stuck on" the skin, with a greasy, warty surface. SKs are primarily seen in adults and older individuals: most people first notice one in middle adult life, and the condition becomes more common with age, affecting almost all adults who are 60 years of age or older. ^[1]

How it is recognised. The stuck-on, warty, "greasy" surface is the classic clue, but morphology varies. A deeply pigmented SK can be difficult to separate from melanoma on naked-eye inspection, which is where dermoscopy matters. Under the dermatoscope, SK shows milia-like cysts, comedo-like openings, a gyrated surface and hairpin vessels. ^[13]

When to act. SK is benign, so treatment is not necessary. Remove it only when it catches on clothing, becomes irritated, or for cosmetic reasons. For raised lesions curettage and cautery is appropriate; flat lesions respond to cryotherapy. Biopsy by excision should be avoided when the diagnosis is clear, because it is more invasive and gives a worse cosmetic result; an inflamed or suspicious SK may need a biopsy to exclude malignancy. ^[13]

Regional guidance differs here. NICE quality standards state that any patient undergoing specialist assessment of a pigmented lesion must be examined with a dermatoscope. ^[13] The Primary Care Dermatology Society also reminds clinicians that if there is any uncertainty about the diagnosis, the patient should be referred urgently on a skin cancer pathway. A sudden eruption of many SKs (the Leser-Trélat sign) is a paraneoplastic phenomenon most often linked to an underlying colonic adenocarcinoma and warrants investigation for internal malignancy rather than local treatment of the skin. ^[1]

Melanocytes are the pigment-producing cells of the skin. When they cluster together they form a melanocytic naevus (a mole). ^[10]

Acquired moles develop during childhood and early adult life. The number of moles increases up to the age of 30 to 40, after which the count tends to fall. ^[10] Congenital naevi are present at birth or appear in the first two years; they are classified by size (small, medium, large or giant). Large and giant congenital naevi, especially when multiple, carry a greater risk of melanoma and are managed as a separate specialist topic.

Acquired melanocytic naevi fall into three histological levels, each with a predictable clinical look: ^[10]

Rarer variants that a student should at least recognise are the blue naevus (a harmless dark blue mole) and the halo naevus (a mole surrounded by a pale ring that often disappears on its own). ^[10]

Risk of melanoma from a mole. There is a small risk of melanoma arising in any individual mole, but the risk is higher in people with more than 20 moles, pale skin and red hair. The stronger determinant is not the mole itself but excessive or recurrent sun exposure: most melanomas arise on previously normal skin rather than from a pre-existing mole. ^[10]

Management. Most moles are best left alone. Removal is indicated when there is diagnostic doubt (the whole lesion is excised with a rim of normal skin and sent for histology), when a mole is repeatedly traumatised, or for cosmetic reasons (which is not funded in the UK system). Lasers are not recommended because no specimen reaches the pathologist. ^[10] A mole that is irritated by clothing or minor trauma may simply be removed by shave excision; multiple, confluent or atypical lesions need a documented plan and photography.

A dysplastic naevus is a melanocytic naevus that looks odd: it is a mole in which the melanocytes have become irregular. The term "dysplastic" means the mole is unusual in appearance but is not cancerous. ^[11]

Recognition. A dysplastic naevus is usually larger than a normal mole, measuring 5 to 10 mm or more, with irregular, indistinct borders and multiple colours (tan, brown, pink and black). It may be flat or raised. ^[11]

Who gets them. People with lighter skin are more likely to develop dysplastic moles; about one in fifteen white people has at least one. Risk factors include fair or red-haired/blue-eyed skin, a previous dysplastic mole, bad sunburn in childhood, and the inherited atypical mole syndrome. ^[11]

Atypical mole syndrome is a rare inherited condition in which a person has numerous, often more than 50, melanocytic naevi that are clinically atypical. ^{[2] [11]}

Malignant potential. The dysplastic naevus itself rarely transforms, and removing all dysplastic naevi does not prevent melanoma, because most melanomas arise de novo. What matters is that the patient with atypical naevus syndrome carries a substantially raised lifetime risk of melanoma and that the many irregular moles make early melanoma harder to spot. ^[11]

FAMMM syndrome. Familial atypical multiple mole melanoma (FAMMM) syndrome, also called dysplastic naevus syndrome, is the familial form: numerous clinically atypical naevi (often more than 50), a significantly increased lifetime risk of melanoma, and germline mutations most often in CDKN2A, and less often CDK4 or ARF. About 5 to 10 percent of cutaneous melanomas have a hereditary predisposition, and among those, roughly 20 to 40 percent carry CDKN2A mutations. Reported patients have developed up to 50 primary melanomas. Patients with FAMMM also have an increased risk of pancreatic carcinoma and other internal malignancies. ^[2]

Management. A mole very different from the patient's other moles, or with evolving change, should be excised under local anaesthetic and examined histologically. If histology shows mild or moderate dysplasia and the lesion is completely excised, no further surgery is usually needed; more severe (high-grade) dysplasia may warrant re-excision with a small margin of healthy skin. When a patient has many dysplastic moles, removing them all is impractical: the plan becomes total-body photography, regular self-surveillance with the ABCDE rule and dermatoscopic follow-up of selected lesions. ^{[11] [1]}

A dermatofibroma, also called fibrous histiocytoma, is a common benign cutaneous soft-tissue lesion made of a dermal proliferation of fibroblasts. It presents as a firm subcutaneous nodule, most often on the limbs, relatively small (typically 1 cm or less in diameter), and usually asymptomatic. It occurs at all ages but is more common between 20 and 50 years, especially in women. Dermatofibromas can follow minor trauma such as insect bites or superficial puncture wounds. ^[3]

Recognition. The lesion is firm and anchored to the epidermis: pinching it makes the overlying skin dimple (the "dimple" or pinch sign). Colour ranges from pink or light brown in pale skin to dark brown or black in darker skin; some are paler centrally. Dermoscopy shows a central white scar-like patch with a peripheral delicate pigment network. ^[3]

Management. No treatment is required. Excision (with subcutaneous tissue, so the lesion is fully removed), intralesional steroid injection or laser can be used for cosmetic or symptomatic reasons, or when there is any diagnostic uncertainty or concern about an aggressive variant. When excision is indicated, a small margin of healthy skin is generally adequate for typical lesions, because local recurrence is reported. The main risk of leaving the lesion is trauma from shaving; the main risk of removing it is a scar worse than the original nodule, which argues against cosmetic removal of a typical dermatofibroma. Histology must exclude dermatofibrosarcoma protuberans, a more aggressive cutaneous neoplasm that looks similar. ^[3]

A lipoma is a benign neoplasm composed predominantly of mature adipocytes, usually enclosed by a delicate capsule or pseudocapsule in the subcutaneous plane. Most are slow-growing, mobile and painless, and feel softer when the adjacent muscle relaxes. Common sites are the trunk, shoulder girdle, neck and proximal extremities, but lipomas can arise wherever fat is present, including the hand, foot, parotid, mediastinum and retroperitoneum. The natural history is years of slow, indolent enlargement followed by stability. ^[4]

Recognition. Diagnosis is clinical: a soft, lobulated, mobile subcutaneous mass that is not tethered to the skin. Deep, rapidly growing, fixed or painful masses are not ordinary lipomas and need imaging and often biopsy: liposarcoma, the malignant counterpart, grows rapidly, does not move under the skin and is often painful. ^[4]

Management. Simple lipomas need no treatment. Remove a lipoma when it is symptomatic, enlarging, cosmetically troublesome or of uncertain diagnosis. Complete marginal excision and submission of the specimen for histopathology is the standard definitive treatment; liposuction can debulk large lesions but does not provide a specimen. If imaging is consistent with an ordinary superficial lipoma and the lesion is small, watchful waiting is reasonable. ^[4]

An epidermoid (epidermal inclusion) cyst is a benign, epithelium-lined cavity filled with keratin in the dermis or subcutis. The familiar name "sebaceous cyst" is inaccurate: the cyst contains keratin, not sebum. It presents as a round or oval, skin-coloured to yellow-white, mobile nodule with a central punctum (the tiny black dot marks the communication with the epidermal surface). Most measure a few millimetres to a few centimetres, enlarge slowly and are asymptomatic until they rupture or become inflamed. ^[5]

Recognition. The central punctum and the expressible cheesy, malodorous keratin are the diagnostic clues. Common sites are the face, scalp, neck, upper trunk and back. Rupture into the dermis produces sudden pain, redness and swelling that can be mistaken for infection; the reaction may be a foreign-body response to keratin rather than bacterial infection. ^[5]

Management. No treatment is needed for a quiet cyst. If it is removed, the whole cyst wall must come out (otherwise it recurs), ideally when the lesion is not inflamed; inflamed cysts are often best treated with antibiotics and incision and drainage first, with definitive excision later. All excised cysts should be sent for histology to exclude the uncommon cyst-like malignancies. ^[5]

"Haemangioma" covers two clinically different groups: the vascular tumours of infancy (infantile haemangiomas) and the little acquired red papules of adults (cherry angiomas). Both are benign, but they are not managed the same way.

An infantile haemangioma is the most common benign tumour of infancy. It is produced by endothelial cell proliferation and appears after birth (congenital haemangiomas, by contrast, are fully formed at birth). IH typically grows rapidly in early infancy, then involutes slowly over years; most resolve without treatment. ^{[6] [14]}

Epidemiology. IH affects about 4 to 10 percent of infants and is more common in females (ratio around 3 to 1), in premature or low-birth-weight infants, and in white infants; most regress, with about 90 percent slowly involuting into fibrous and fatty tissue by school age. ^{[6] [14]}

When to treat. Only about 10 percent of IH need intervention. Treatment is reserved for lesions that are life- or function-threatening, ulcerated, or likely to leave significant scarring or permanent deformity: airway or hepatic haemangiomas, visual or feeding impairment, large facial lesions, and ulcerated haemangiomas of the lip or perineum. ^[14]

First-line treatment. Oral propranolol is now the first-line medication for IH. It is started at 0.7 to 1.0 mg/kg/day and titrated up to a target of 2 to 3 mg/kg/day in two or three divided doses, with monitoring of heart rate and blood pressure after the first dose and each increase. The course is 6 months for larger lesions, often continuing to 12 months or more, with a high response rate. Propranolol can be taken at home only in infants without risk factors; high-risk infants (airway, large segmental facial, very young) should be treated and monitored in hospital. ^[14]

Topical timolol is used for small superficial haemangiomas; surgery, pulsed-dye laser and sclerotherapy are now reserved for lesions that fail medical therapy or require reconstruction. Systemic corticosteroids are no longer first line. ^[14]

Red flags in IH that warrant early specialist discussion are ulceration, airway symptoms, visual compromise, large segmental facial lesions (which may be associated with PHACE syndrome), multiple small haemangiomas (which may signal hepatic haemangiomas), and any haemangioma in early infancy. ^{[6] [14]}

Cherry angiomas are common benign acquired vascular proliferations of adult skin, also called Campbell de Morgan spots, senile angiomas or ruby spots. They are red, dome-shaped papules 1 to 5 mm in size, most often on the trunk or upper limbs; lesions are multiple, increase in number with age, and may bleed if traumatised. They are excluded from the current ISSVA classification of vascular tumours despite their distinct histology (lobular capillary proliferation in the papillary dermis). Cherry angiomas are harmless and need no treatment; electrocautery, laser or cryotherapy are used only for bleeding or cosmetic reasons. ^[7]

A pyogenic granuloma is a common, acquired, benign vascular tumour of skin or mucous membrane. The name is a misnomer: it is neither pyogenic nor a granuloma. Histologically it is a lobular capillary haemangioma. It appears as a solitary, red, very friable, bleeding-prone pedunculated papule that may be sessile; it grows rapidly and its surface often ulcerates. Sites include the hands, fingers, face and, most commonly among mucosal lesions, the gingiva in pregnancy ("granuloma gravidarum"), usually in the second or third trimester. ^[8]

Management. Pyogenic granulomas rarely settle on their own. Surgical excision with linear closure is preferred because it gives a complete specimen for histology and has the lowest recurrence; curettage, shave excision and cautery carry a higher recurrence. Topical timolol or imiquimod can shrink or clear selected small lesions. Every excised lesion must be sent for histology: amelanotic melanoma and other tumours (including metastatic renal cell carcinoma) can mimic a pyogenic granuloma. ^{[8] [13]}

Salt therapy (daily salt under an occlusive dressing) and local excision after the lesion has involuted are both used in pregnancy, where many granulomas regress after delivery. Pregnancy-related granulomas should not be over-treated in the first trimester. ^[8]

Skin tags are benign soft excrescences of redundant skin. About 50 to 60 percent of adults develop at least one in their lifetime, more often after the fourth decade, and tags are more common with obesity, diabetes mellitus, metabolic syndrome and a family history. Men and women are equally affected; tags are rare after the seventh decade. They occur in skin folds (neck, axilla, eyelids, groin) and are skin-coloured, brown or red, often pedunculated, and 1 to 5 mm long (rarely up to 1 to 2 cm). ^[9]

Associations. Multiple skin tags can be associated with acanthosis nigricans and insulin resistance, and with genetic syndromes such as Birt-Hogg-Dubé and tuberous sclerosis. ^[9]

Management. Tags are harmless and need no treatment. Remove them when they catch on clothing or jewellery, bleed, itch, or for cosmetic reasons, by snipping with scissors under local anaesthetic, radiofrequency ablation, cryosurgery or simple cautery. A "necklace" of many tags can be treated in one session. A tag that is pigmented, shows recent change, or looks atypical should be excised (not snipped) and sent for histology to exclude melanoma. ^[9]

• Children. Infantile haemangioma is the commonest tumour of infancy, not adults; congenital melanocytic naevi and dermatofibromas can appear in childhood. New or enlarging pigmented lesions in a child merit careful documentation and review.
• Pregnancy. Melanocytic naevi usually stay the same in pregnancy (apparent growth is skin stretching); granuloma gravidarum is common on the gingiva; pyogenic granulomas of pregnancy often regress after delivery.
• Older adults. Seborrhoeic keratoses, dermatofibromas and cherry angiomas cluster in older people; the risk of a new pigmented lesion being melanoma rises with age, so age itself lowers the threshold to excise or refer.
• Immunosuppressed patients. Skin cancers (especially squamous cell carcinoma) are commoner and more aggressive; their "benign" lesions are biopsied more readily.

• Recognition and history do most of the work. A dermatoscope is the single most useful affordable tool and is justified by NICE's quality standard: even a simple handheld dermatoscope removes much diagnostic uncertainty. ^[13]
• Where histology is unavailable, excise rather than shave or curette whenever there is any doubt: destroying the lesion removes the diagnosis. Photograph the lesion before removal, with a ruler for scale.
• Cryotherapy with liquid nitrogen, electrodesiccation and curettage are cheap and effective for seborrhoeic keratosis and skin tags; a sterile disposable punch handles dermatofibroma and the small suspicious mole.
• Sun protection and total-skin self-examination cost nothing and matter more than any procedure in preventing melanoma.
• Refer early on a cancer pathway if a lesion scores 3 or more, grows, ulcerates, or looks different from the patient's other lesions.

• Seborrhoeic keratosis is a stuck-on, warty, brown-black lesion of middle and older age, benign and not requiring treatment; cryotherapy for flat lesions, curettage and cautery for raised ones; dermoscopy to separate it from melanoma. ^{[1] [13]}
• Melanocytic naevi are classified by level (junctional, compound, intradermal); most are best left alone; laser removal is not recommended because no histology is possible. ^[10]
• About one in fifteen white people has at least one dysplastic naevus; these moles rarely transform but mark higher melanoma risk and are managed by selective excision plus surveillance. ^[11]
• FAMMM syndrome (often more than 50 atypical naevi, CDKN2A mutations, raised melanoma and pancreatic cancer risk) needs regular surveillance and genetic counselling. ^[2]
• Dermatofibroma is a firm, 1 cm or smaller, dermal fibrohistiocytic nodule, often after minor trauma; no treatment is needed; excise with a small margin if necessary. ^[3]
• Lipoma is a soft, encapsulated, mobile subcutaneous fat tumour; remove only if symptomatic, uncertain or large, and always submit the specimen. ^[4]
• Epidermoid cysts contain keratin (not sebum); a central punctum points to the diagnosis; removal requires the whole wall. ^[5]
• Infantile haemangioma is the commonest tumour of infancy, grows then involutes; only about 10 percent need treatment, and oral propranolol at 2 to 3 mg/kg/day is first line. ^{[6] [14]}
• Cherry angiomas (1 to 5 mm red dome papules increasing with age) are harmless and need no treatment. ^[7]
• Pyogenic granuloma is a rapidly growing, bleeding-prone vascular papule; excision has the lowest recurrence and histology is mandatory because of mimics. ^[8]
• Skin tags (1 to 5 mm) are common, harmless and associated with obesity, diabetes and metabolic syndrome; excise atypical or changing tags. ^[9]
• Dermoscopy is expected for pigmented lesions, and a NICE weighted 7-point score of 3 or more sends the patient on a suspected cancer pathway. ^[12]

Benign skin tumours and naevi are rarely diagnosed without thinking about melanoma. Related reading includes MedGrasp topics on melanoma and other skin cancers, chronic sun damage, dermatoscopy, and vascular anomalies, together with the topics on obesity, insulin resistance and pregnancy for the systemic associations mentioned above. (Some of these may not yet be published as MedGrasp pages.)