Picture Quiz

Case history

An 86 year old woman was admitted to hospital with a right lower lobe pneumonia. Sputum grew Streptococcus pneumoniae, and the patient responded well to treatment with antibiotics. Three weeks after admission she was transferred to a rehabilitation hospital to improve her mobility. Although seen by several doctors none had commented on a pigmented lesion on the left side of her cheek (figure 1). On specific inquiry the patient reported having had the skin lesion for at least 20 years. She had noted that it had increased slowly in size but did not think that it was important and had never sought a medical opinion about it. Following a dermatology review the lesion was biopsied and subsequently surgically removed.

Questions

(1) What is the skin lesion?
(2) Give two differential diagnoses.
(3) What is the prognosis?

Answers

(1) Lentigo Maligna (Hutchinson's melanotic freckle).

(2) Actinic lentigo, flat seborrhoiec wart, melanocytic naevus.

(3) Although premalignant, prognosis is good. The lesion is slow growing and it is rare for patients to die of it. Even if nodular formation takes place (malignant melanoma, histologically) it rarely metastasises.

Discussion

Melanoma is a tumour arising from melanocytes. Up to 40% of cases develop in melanocytic naevi but a significant percentage arises de novo from normal skin. Melanoma is a tumour found predominantly in white people. While the incidence is low in black and Asian people, it is highest in white people living at low altitudes - for example, in Queensland in Australia. Malignant melanoma is the most common fatal skin cancer and incidence has increased by a factor of 15 in the past 60 years. The factors underlying the increased incidence are not completely understood but increased total exposure to sunlight and altered patterns of exposure (intense intermittent exposure) seem to be associated with risk. Familial melanomas occur rarely. In the United Kingdom approximately 1% of patients have a strong family history of melanoma, and two predisposing genes have been identified.

Another risk factor is the presence of abnormal naevus phenotype, the atypical mole syndrome. In this condition patients have large numbers of moles, moles are atypical, and large numbers occur in unusual sites - for example, the buttocks and the soles of the feet.

People at particular risk of melanoma are those with red hair, those with large numbers of naevi moles, and those with three or more cases of melanoma in the family. There are four clinical types of melanoma:

(1) Superfical spreading, which is the commonest.
(2) Nodular melanoma, which is fast growing and has the poorest prognosis.
(3) Lentigo maligna, which is usually on the face for many years.
(4) Acral lentiginous, which is rare and occurs on the soles of the feet, palms, and under nails.

Prognosis for all melanomas is determined by the Breslow thickness. This is the distance in millimetres from the granular layer of skin down to the deepest part of the tumour. Tumours larger than 3.5 mm have 36% disease-free survival at five years.

Lentigo maligna lesions present usually on the face in middle aged and elderly people. The lesions begin as irregular flat areas of pigmentation and slowly increase in size over years. Pigmentation is often irregular. After many years the lesion may become nodular (malignant melanoma). Diagnosis is usually obvious but if there is any doubt biopsy should be performed. In the macular stage cryotherapy is the treatment of choice. If a nodular lesion develops, surgery is the best treatment. Prognosis is usually good, because the lesion is slow growing and, even if nodular formation occurs, it rarely metastasises.

Rosemary Morgan, consultant physician in medicine for the elderly, Department of Medicine for the Elderly,Wirral Hospital, Merseyside


studentBMJ 2001;09:171-216 June ISSN 0966-6494