Premalignant lesions

  Actinic keratoses

Actinic keratoses (senile keratoses, solar keratoses) are areas of epidermal dysplasia giving rise to cutaneous scaling, usually observed in sun-exposed fair skin. These lesions are potentially malignant. Superficial lesions are best removed by rapid and even freezing with carbon dioxide or liquid nitro­gen on a cotton wool bud. Diathermy preceded by curettage of horny lesions is equally effective, but more likely to leave superficial scarring. Indurated lesions are best excised. Multiple lesions may clear with topical 5-fluorouracil cream. An effective sunscreen is important as improvement follows avoidance of sunlight, which is also important prophylactically. Radiotherapy should not be used for solar keratoses.

Bowen’s disease

Bowen’s disease is an intraepidermal squamous cell carci­noma that is potentially malignant and appears as a persistent, progressive, usually flat, red, scaly or crusted plaque (Fig. 13.32). It is more frequently seen in the elderly. It is triggered mainly by solar radiation, but if those keratoses with Bowen’s features are separated off, the cause most frequently found is arsenic ingestion. Most patients are unaware of having been exposed to arsenic as its presence in a mixture taken medically may have been concealed from them or forgotten. The rate of transformation of Bowen’s disease to invasive squamous cell carcinoma is still disputed. Untreated, 3—5 per cent of patients will develop an invasive squamous cell carcinoma. The possibility of a viral cause of Bowen’s disease has been postulated. The lesions most likely to be mistaken for Bowen’s disease are solar keratoses, psoriasis, multifocal (superficial) basal cell carcinoma and squamous cell carcinoma. If the diagnosis is uncertain on the first examination, the lack of improvement when steroids are applied is suggestive of Bowen’s disease. Distinction from the flat type of solar keratosis may be impossible clinically. A biopsy may be necessary to establish a diagnosis. Locally destructive therapy such as cryotherapy or curettage and cauterisation is often used. Recurrence may be due to inadequate treatment of the superficial tumour or failure to destroy deeper extensions down appendage structures such as hair follicles. Radiotherapy, if used, has to be in full tumour doses. Chemotherapy with local cytotoxic agents such as 5-fluorouracil can be applied to small lesions with good effect. Surgical excision is the best treatment if the lesion is not too large.

Erythroplasia of Querat

Erythroplasia of Querat describes Bowen’s of the glans penis. It occurs most commonly in uncircumcised males.

Radiodermatitis

This is an area of skin damaged by excessive exposure to X­irradiation. Early erythema occurs which goes on to desquamation and pigmentation. If the dose is very great ulceration may occur. Later atrophy, irregular hyperpigmentation, telangiectasia and hair loss occur. Eventually, squamous cell carcinoma may develop.

Chronic scars

A carcinoma which develops in a scar (Marjolin’s ulcer) (Fig. 13.33) presents the following characteristics. It grows slowly, as the scar is relatively avascular. It is painless, as scar tissue contains no nerves. Secondary deposits do not occur in the regional lymph nodes as lymphatic vessels have been destroyed. If the ulcer invades normal tissue surrounding the scar, it extends at a normal rate, and lymph nodes are then liable to be involved.

Sebaceous epidermal naevus

Sebaceous epidermal naevus (of Jadassohn, organoid naevus) (Fig. 13.34) is a common condition, frequently affecting the scalp. It initially appears as a raised papular yellow area, developing into a papillomatous area as the child matures. Up to 10 per cent of these may develop into basal cell carcinomas. Very rarely these develop into syringo­cystadenoma papilliferum — an anomaly of the apocrine gland. Treatment consists of complete excision.

  Porokeratosis

Porokeratosis (of Mibelli) is characterised by annular plaques with horny borders. About 13 per cent may transform into basal cell or squamous cell carcinomas.