Clinical types

Classical type: present at birth or appears in the first three decades; grouped soft papules, nodules or plaques, often on lower back, buttock, pelvic girdle or upper thigh.
Classical lesions may be linear, segmental or zosteriform; the surface can be smooth, wrinkled, pedunculated, sessile, cerebriform, hairy or comedo-like.
Solitary type: tends to arise after the second decade as a single soft, yellow or skin-coloured dome-shaped papule, nodule or swelling anywhere on the body.
Usually asymptomatic; the main concern is appearance or mechanical irritation.
Rarely, large lesions can ulcerate or undergo superficial necrosis from trauma or pressure.

Histology and diagnosis

Diagnosis is confirmed histologically.
Mature adipocytes are found in the dermis, often between collagen bundles and around vessels or adnexal structures.
The adipocytes are not connected to the subcutaneous fat, which helps distinguish the lesion from ordinary lipoma.
The overlying epidermis may show papillomatosis, acanthosis or basal pigmentation.
Biopsy or excision is reasonable if the lesion is atypical, ulcerated, enlarging, diagnostically uncertain or clinically mimics another tumour.

Classical type: neurofibromatosis, lipoma, sebaceous naevus, verrucous epidermal naevus and connective-tissue naevus.
Solitary type: acrochordon/fibroepithelial polyp, lipoma, accessory nipple, lymphatic malformation, haemangioma, neurofibroma, trichoepithelioma and cylindroma.
Soft cerebriform plaques on the lower trunk/buttock should also prompt consideration of plexiform neurofibroma and focal dermal hypoplasia if syndromic features are present.
If a presumed skin tag or lipoma has unusual texture, congenital history, grouped distribution or marked dermal component, histology is helpful.

No treatment is required for a typical, asymptomatic lesion once diagnosis is secure.
Excision is the preferred treatment when intervention is needed for cosmesis, repeated trauma, ulceration, symptoms or diagnostic uncertainty.
Large classical lesions may need staged excision or reconstructive planning if removal is requested.
Laser/ablative approaches have been reported but may leave residual dermal adipocytes and are less definitive than excision.
There is no recognised malignant transformation risk; prognosis is excellent.

Do not assume every soft pedunculated lesion is a skin tag; congenital grouped or cerebriform lesions deserve a wider differential.
Do not diagnose ordinary lipoma if histology shows adipocytes within dermis rather than a subcutaneous encapsulated fat tumour.
Ulceration is uncommon and should trigger review for trauma, pressure and alternative diagnoses.
Document extent before treatment; removal for appearance can be reconstructively more involved than the benign diagnosis suggests.