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January 2007: Pigmented lesions

What is the significance of a halo around a mole?

How can seborrhoeic keratosis be distinguished from a melanoma?

Which pigmented lesions need referral to a dermatologist?

What is the significance of a halo around a mole?

How can seborrhoeic keratosis be distinguished from a melanoma?

Which pigmented lesions need referral to a dermatologist?

?The pigmented lesion is a diagnostic challenge in primary care. the incidence of melanoma is increasing,1 and pigmented lesion clinics are overburdened, sometimes by inappropriate referrals.

The possibility that a lesion could be malignant means that careful assessment is always required. The number of deaths caused by malignant melanoma has increased steadily from one per 100,000 in 1971 to 2.6 per 100,000 in 2001 for men, and from 1.4 per 100,000 to two per 100,000 for women during the same time period.2 Many of these deaths occur in young patients.

Dermoscopy3 is one way to aid diagnosis of lesions but this is a new specialty and will take time to perfect. At present its use is usually confined to secondary care and GPSIs.

For GPs who are not proficient in dermoscopy, there are other helpful criteria that may be applied, such as the Glasgow seven-point check list,4 which includes red flags for malignancy.

The major red flag signs are:

• A change in size

• An irregular pigment and border

The minor signs are:

• Inflammation

•Altered sensation

• Itchiness

• Oozing and crusting

• A lesion larger in size than other lesions on the patient.

A more simple system is the ABCDE criteria, which considers asymmetry, border, colour, diameter (>6mm) and elevation as diagnostic criteria.5

When a combination of these signs suggest that a lesion may be a melanoma, a GP can refer the patient under the two-week wait scheme.

The NICE guidance on improving outcomes for people with skin tumours including melanoma, published in February 2006,1 does not recommend the management of melanoma in primary care. However, this may be possible for dermatology GPSIs, especially if patients are managed under the guidance of a local multidisciplinary team for skin cancer based in secondary care.

1 Melanocytic naevus

Melanocytic naevi occur in almost all white patients. Some are present from birth, but more commonly they develop in adolescence and then disappear in later life. It is uncommon to find melanocytic naevi in the elderly.

Melanocytic naevi are categorised as junctional, compound, dermal or blue, depending on their position in the skin.

2 Blue naevus

Blue naevi occur when the melanocytes from the neural crest fail to arrive at the dermoepidermal junction. Instead, the melanocytes are found in the lower dermis, and give a blue appearance when light is refracted at this level.

These lesions are benign, and most common on the hands and neck. Patients can be reassured that they do not undergo malignant change. If the diagnosis is uncertain the lesions should be excised.

3 Spitz naevus

Also known as juvenile melanoma, the spitz naevus is frequently reported histologically as a malignant melanoma. However, the average age of patients with this lesion is ten years, and melanomas are very rare in children of this age. Presenting as a red or brown, dome-shaped papule, morphologically the spitz naevus does not resemble a typical melanoma. It most commonly occurs on the face, especially the cheeks, where it grows rapidly.

Unlike the majority of compound naevus lesions, the spitz naevus is a benign condition. The lesion itself contains little true pigment; the colour is derived from ecstatic blood vessels found in its stroma.

4 Halo naevus

Usually presenting on the trunks of teenagers, halo naevi are relatively common pigmented lesions. Over a period of time, the halo will increase in size and the pigment will decrease until the lesion disappears completely. This is thought to be an autoimmune process. Antibodies isolated from these patients have been shown to be directed against malignant melanoma cells in vitro.6 The condition is benign, but there is an increased incidence of vitiligo in patients who exhibit this lesion at an early age.

5 Sebaceous naevus

This is a relatively common lesion on the head and neck, often affecting the scalp. It is well circumscribed, and raised with a yellow pigmentation. Upon closer inspection, multiple raised elevations across its surface and an absence of hair within the body of the naevus can be observed. Often present at birth, the lesion will decrease in size as the effect of maternal androgens is lost, only to increase in size during puberty. As the lesion may undergo malignant change, excision is the treatment of choice.

6 Naevus of ota

Histologically indistinguishable from the more common Mongolian blue spot, the naevus of Ota affects one side of the face in the distribution of the ophthalmic and maxillary divisions of the trigeminal nerve. The sclera is often affected, as in this case.

A similar condition, the naevus of Ito, affects areas supplied by the posterior supra-clavicular and lateral brachial cutaneous nerves.

7 Post inflammatory hyperpigmentation

This is probably the most common cause of increased pigmentation within the skin, and usually occurs in black, Asian and Latin American patients. Any inflammatory condition, such as acne, psoriasis or, as in this case, eczema, can cause increased pigmentation. Careful history taking is important, as in many cases the precipitating inflammatory condition will have resolved by the time the patient presents. Some conditions, such as lichen planus, cause hyperpigmentation in almost every case, regardless of ethnicity.

A variety of topical agents have been used, with varying degrees of success. These agents include hydroquinone, tretinoin cream, corticosteroids, glycolic acid, and azelaic acid.7 Camouflage make-up can be used in all cases.

8 Pigmented seborrhoeic keratosis

Seborrhoeic keratosis is a very common, benign skin tumour. It occurs with increasing frequency with age. The lesions are often pigmented, giving rise to concern that they may be malignant, especially when a solitary lesion is present. They are most common on sun-exposed areas, such as the face, hands, arms and trunk.

The condition occurs when keratinocytes fail to mature, resulting in the accumulation of immature, benign cells in the epidermis. The pigmented appearance is caused by the transfer of melanin into the cells by neighbouring melanocytes.

The lesions have a rough surface and fine fissures, and look as if they have been attached to the skin.

Although the lesions are of no clinical significance, seborrhoeic keratoses are unsightly and may itch and bleed, leading to requests for their excision. This is easily performed in the primary care setting, either by curettage and cautery or the application of liquid nitrogen.

9 Accidental tattooing

It is always important to think laterally when a patient presents with a strange lesion, and to consider if the lesion is self-inflicted.

In this case the lesion was obviously pigmented, but was present only on the finger and had a very artificial, linear distribution. The patient was otherwise asymptomatic.

The diagnosis was obtained by taking a careful history. For most of his life the patient had worked as a coal miner. He had cut his finger deeply one day but had carried on working, during which time coal dust was deposited in the wound, leaving the finger permanently tattooed.

10 Dermatofibroma

This benign tumour is more common in women, and tends to occur on the lower legs. Raised and firm to the touch, the lesions are commonly pigmented and are often mistaken by patients for moles. In most cases they are precipitated by an old injury, such as an insect bite or thorn wound. The lesions are attached to the skin but not adherent to underlying tissue. The dimple sign,8 seen in the photo where the lesion dimples when pressure is applied, is important in diagnosis but not unique to dermatofibroma. Although excision is not required, it is often requested for cosmetic reasons.

11 Lentigo maligna

Also known as Hutchinson's freckle, this type of lesion is most common in elderly patients. Initially developing as a malignant melanoma in situ, it grows very slowly, but may change to an invasive lentigo maligna melanoma.9 Lentigo maligna is caused by UV damage, and is most common on the face.

Although the potential for invasion means that excision is the treatment of choice, these lesions are often large and the procedure can be technically difficult, so watchful waiting is often the approach adopted. Radiotherapy and cryotherapy are also options.

12 Malignant melanoma

The median age for the diagnosis of malignant melanoma is 62 in men and 60 in women.10

This case shows the typical variation in pigment, asymmetrical growth pattern and early nodules.

The incidence of malignant melanoma has risen sharply from two to three per 100,000 in 1971, to 10 to 11 per 100,000 in 2001.1 This equates to 6,432 new cases registered in England and Wales in 2001.11 There were 1,500 deaths from malignant melanoma that year.10 It is the third most common tumour type in the 15 to 39 age group.

Despite a rise in the incidence of melanoma, the survival rate has improved. The five-year survival for men has increased from 72.9 per cent of men diagnosed between 1991 and 1995 to 76.5 per cent for those diagnosed between 1996 and 1999. For the same time periods, five-year survival for women increased from 85.1 per cent to 87.3 per cent. These increases are statistically significant.12

Melanocytic naevi are found in almost all white patients, and typically disappear with age Figure 1: Melanocytic naevus Blue naevus. The blue appearance is caused by light refraction in the lower dermis Figure 2: Blue naevus Spitz naevus. This benign lesion commonly occurs on the face Figure 3: Spitz naevus Halo naevus. Over time the halo will increase in size and the pigment will disappear Figure 4: Halo naevus Sebaceous naevi may undergo malignant change and should be excised Figure 5: Sebaceous naevus Naevus of Ota. The sclera is often affected Figure 6: Naevus of Ota Post inflammatory hyperpigmentation. Any inflammatory condition can precipitate the increase in pigment Figure 7: Post inflammatory hyperpigmentation Pigmented seborrhoeic keratosis. Excision can be performed in primary care Figure 8: Pigmented seborrhoeic keratosis Accidental tattooing with coal dust Figure 9: Accidental tattooing Dermatofibroma is often precipitated by an old injury

at the site Figure 10: Dermatofibroma Lentigo maligna. The potential for change to an invasive melanoma means that excision is the treatment

of choice Figure 11: Lentigo maligna Malignant melanoma. This case shows the typical variation in pigment, asymmetrical growth pattern and early nodules

Figure 12: Malignant melanoma Author

Dr Nigel Stollery
GP, Kibworth, Leicestershire and clinical assistant in dermatology, Leicester Royal Infirmary

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