Chapter 45: Skin and Subcutaneous Tissue

Ethnic differences in skin colour are determined by differing melanocyte numbers between ethnic groups.

The surface of human skin is normally slightly alkaline.

The dermis contains both capillaries and lymphatics.

The skin has mechanical, endocrine, homeostatic, excretory and sensory functions.

Skin is thinner in children and the elderly.

Basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) caused by ultraviolet radiation share a common originating step of damage to the gene p53.

Chromosome 9 is commonly affected in genetically linked syndromes producing high rates of skin cancer after ultraviolet exposure.

The concept of ‘high-risk’ and ‘low-risk’ lesions with respect to prognosis applies to both basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) and the inclusion criteria overlap.

The preoperative margins of excision should be marked using optical magnification.

Prognosis is worse for thicker squamous cell carcinomas (SCCs) for similar reasons to worsening prognosis with increasing thickness in melanoma.

Haemangiomata are commoner in girls than in boys and usually resolve with increasing age.

Vascular malformations are commoner in boys than in girls and are associated with numerous genetic syndromes.

Vascular malformations may be associated with haematological and skeletal pathology.

Vascular skin lesions can be treated with intense pulsed light or laser targeted at haemoglobin (as a chromophore).

Pyogenic granulomata usually respond readily to laser treatment.

Most neurofibromatosis is the result of spontaneous mutations.

Hidradenitis suppurativa is commoner in women.

Pyoderma gangrenosum and necrotising fasciitis are surgical emergencies needing intervention without delay.

Most superficial skin infections are caused by staphylococci and/or streptococci.

After screening blood tests and radiology, the vital management of necrotising fasciitis is fluid resuscitation, rapid administration of high-dose intravenous broad-spectrum antibiotics and surgical debridement.

Where melanoma is suspected, an initial biopsy followed by definitive clearance based on the thickness of the melanoma is the only safe management.

Histologically confirmed metastasis to regional lymph nodes has more prognostic significance than the Breslow thickness of the primary melanoma.

It is likely that positive sentinel node biopsy (SNB) followed by regional lymphadenectomy confers no measurable survival benefit because, in the majority of cases, the SNB removed the only metastatic disease present.

Lentigo maligna melanoma is positively correlated with prolonged sun exposure.

Nodular melanoma is generally more aggressive than superficial spreading melanoma; more common in men; and more commonly arises on the upper half of the body.