It’s not cancer: Five common benign skin lesions15 November 2019
Heightened sun safety messaging is making Canadians increasingly familiar with their overall skin health and leading them to physician offices with concerns about suspicious skin lesions. In practice, knowing what skin lesions are not suspect can be as important as knowing what lesions are. Although skin cancer is the most prevalent cancer, the vast majority of skin lesions brought to the attention of physicians are benign. The art of practising medicine often involves effectively communicating to a patient that for many conditions, no treatment is the best treatment. On the following pages are five common but often misdiagnosed benign skin lesions that Canadian practitioners can learn to easily identify and manage.
Seborrheic keratoses or “seb kays” are harmless skin lesions that typically occur in older individuals. They represent discreet, benign proliferations of epidermal cells and are the most common of all skin tumours. Their etiology is unknown; however, they are more common on sun-exposed areas and there may be a genetic predisposition to developing them. Seborrheic keratoses tend to involve the chest or back but can occur anywhere on the skin except the palms, soles and mucosal surfaces. They generally appear as “stuck-on,” wart-like lesions that are tan to brown in colour and can vary in number from one to several hundred. They are often asymptomatic but can be itchy or painful if they catch on clothing or become irritated. Dark-coloured (pigmented) seborrheic keratoses are difficult to distinguish from other suspicious pigmented skin lesions but carry no malignant potential. The sign of Leser-Trélat is the association of an abrupt onset of multiple seborrheic keratoses with internal malignancy, most commonly gastrointestinal adenocarcinoma.1
Dermatosis papulosa nigra lesions are benign variants of seborrheic keratoses that present as small, hyperpigmented, keratotic papules typically developing on the face of patients with darker skin.
The diagnosis of seborrheic keratoses is clinical; however, ambiguous lesions should be biopsied to rule out an atypical nevus or melanoma. The main differential diagnoses of seborrheic keratoses include common warts, epidermal nevi, dermal nevi, dysplastic nevi and melanoma. Treatment of seborrheic keratoses is not necessary but liquid nitrogen is commonly used to remove them. Electrocautery, curettage, surgery and CO2 laser have also been employed.
Granuloma annulare is a benign inflammatory skin condition characterized by single or multiple lesions often arranged in a ringed (annular) configuration. Granuloma annulare is twice as common in women as it is in men, occurs in all age groups and has no racial predilection.
Its etiology is unknown but has been associated with diabetes mellitus. The lesions present as asymptomatic, smooth, erythematous to flesh coloured papules and annular plaques with indurated borders that are always non-scaly. Granuloma annulare has been classified into several forms, including a localized and generalized form. The localized form is the most common (75%)2 and tends to occur in children, with lesions affecting the distal extremities. The less common generalized form tends to occur in adults with lesions affecting the trunk.
The diagnosis is made clinically. It is most often mistaken for either tinea infection (ringworm) or eczema, but differs in that it is asymptomatic and non-scaly in appearance. Other differential diagnoses include psoriasis, pityriasis rosea, urticaria, Lyme disease and sarcoidosis. If the diagnosis of granuloma annulare is unclear, a biopsy should be performed. For mild localized forms, spontaneous involution often occurs and no treatment is necessary. In the generalized form, lesions tend to persist indefinitely. Intralesional and topical corticosteroids are often used as first-line treatments to reduce the clinical appearance of lesions. Other treatment options include cryotherapy, topical immunomodulators and phototherapy. Various systemic treatments have been put forth for more generalized granuloma annulare, but none is uniformly successful.
Sebaceous hyperplasia lesions are benign, small, smooth, often umbilicated yellow papules that typically develop on the face of middle-aged and older individuals. They represent localized proliferations of the sebaceous glands that are normally present all over the skin except the palms and soles. Their etiology is unknown but they are more common in immunosuppressed individuals. Sebaceous hyperplasia lesions are asymptomatic, can be solitary or multiple and tend to persist indefinitely. They are a source of confusion for many practitioners due to their similarity to basal cell carcinoma. They can be differentiated from basal cell carcinoma by their typical yellow colour, lack of bleeding or ulceration and their presence in multiples. Other differential diagnoses include epidermal cysts, seborrheic keratoses and benign nevi. A diagnosis of sebaceous hyperplasia can be confirmed by biopsy. No treatment is required, but electrocautery, surgical removal, chemical peels and lasers3 have all been used successfully.
Dermatofibroma is a benign skin lesion that typically occurs on the lower extremities of middle aged-women. Its etiology is unknown but it is thought to develop in response to minor injuries such as shaving cuts, ingrown hairs or insect bites. Dermatofibromas can occur in all races and at any age but commonly affect young adults. Women are affected four times more commonly than men. The lesions usually present as slow-growing firm pink to brown nodules and tend to be darker in darker-skinned individuals. Dermatofibromas can vary in size from several millimetres to one centimetre and are usually asymptomatic but can be itchy or tender. Pinching a dermatofibroma often elicits a dimpling on its surface, termed the “dimple sign.” The rare, abrupt development of multiple dermatofibromas has been linked to HIV4 and systemic lupus erythematosus. A biopsy should be performed on any lesion if the diagnosis is unclear. The differential diagnosis of dermatofibroma includes atypical nevi, epidermal cysts, keloids, blue nevi, basal cell carcinoma and melanoma. No treatment is required for dermatofibomas; however, they can be surgically excised if irritating or painful.
Pyogenic granuloma or lobular capillary hemangioma is a small, solitary pedunculated, benign vascular tumour of the skin or mucosa that commonly presents in children, pregnant women or young adults. The name itself is a misnomer in that pyogenic granuloma is neither granulomatous nor infectious. It often occurs on exposed surfaces of the nail folds, fingers, forearms, face or sites of trauma. The cause is unknown, but the lesions have been reported to occur in association with retinoids5 and antiretrovirals.6 Pyogenic granulomas present as asymptomatic, raspberry-red, wet-appearing, well-circumscribed papules or nodules that vary in size from several millimetres up to several centimetres. They evolve rapidly over a period of a few weeks and bleed easily on the slightest trauma. Pyogenic granuloma can mimic benign angioma, hemangioma of infancy, squamous cell carcinoma and, rarely, malignant melanoma. The definitive treatment is surgical. Shave excision followed by curettage and electrodessication of the base is one of the most common methods for removal; however, punch or simple excision, laser therapy and cryotherapy can also be used. Pyogenic granulomas recur commonly, irrespective of the treatment modality.
1. Schwartz RA. Sign of Leser-Trélat. J Am Acad Dermatol. 1996 Jul;35(1):88-95.
2. Nopper A, Markus R, Esterly N. When it’s not ringworm: annular lesions of childhood. Pediatr Ann. 1998 Mar;27(3):136-48.
3. Winstanley D, Blalock T, Houghton N, Ross EV. Treatment of sebaceous hyperplasia with a novel 1,720-nm laser. J Drugs Dermatol. 2012 Nov;11(11):1323-6.
4. Armstrong DK, Irvine A, Walsh MY, et al. Multiple dermatofibromas in a patient with HIV infection. Clin Exp Dermatol. 1995 Nov;20(6):474-6.
5. Teknetzis A, Ioannides D, Vakali G, et al. Pyogenic granulomas following topical application of tretinoin. J Eur Acad Dermatol Venereol. 2004 May;18(3):337-9. 6. Bouscarat F, Bouchard C, Bouhour D. Paronychia and pyogenic granuloma of the great toes in patients treated with indinavir. N Engl J Med. 1998 Jun 11;338(24):1776-7