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Pathology

1. From cells of the stratum basale of the hair follicle therefore can never be found in the mouth or glans
2. Exhibit high mitotic rates and peripheral palisading (cell islands arranged radially with long axes in approximately parallel alignment)
3. Often there is ulceration of the epidermis
4. Hedgehog signalling pathway important in embyrological development and is highly conserved through evolution; Patched gene mutations underlie Gorlin's syndrome in which multiple BCCs are a key feature

Approach

• Sit or kneel in front of the patient to be at the same level as his face
• Examine as for any lump

1. Inspect
   
   • Occur in hair bearing sun-exposed skin of elderly people, especially around the eye
   • Single or multiple
   • Features of BCC depend on the clinical type and can be divided:
     

     	Type	Appearance	Features
     Raised above the skin	Nodular		Most common type Well-defined rolled pearly edge Central ulceration
     	Cystic		Large cystic nodule
     Not raised above the skin	Pigmented		Contains melanin Can be confused with malignant melanoma
     	Sclerosing (morphoeic)		Flat or depressed tumour Ill-defined edge may be ulcerated (occurs late)
     	Cicatricial ("bush fire")		Multiple superficial erythematous lesions interspersed with pale atrophic areas
     	Superficial		Erythematous scaly patches Can be confused with Bowen's disease

2. Palpapte
   • Fixation of BCC deep to skin is a sign of deep local invasion

Differentials

1. Benign
   • Keratoacanthoma - especially if it is sloughing at its centre
2. Malignant
   • Squamous cell carcinoma - particularly nodulo-ulcerative type with a rolled edge

Finish

1. Examine for regional lymphadenopathy (metastases are extremely rare)
2. Ask about predisposing factors
   • Congenital (rare)
     1. Xeroderma pigmentosum (familial condition with failure of DNA transcription leading to defective DNA repair) = Kaposi's disease
     2. Gorlin's syndrome
   • Acquired (common)
     1. Sunlight: particularly ultraviolet light
     2. Carcinogens - cigarette smoke, arsenic
     3. Previous radiotherapy
     4. Malignant transformation in pre-existing skin lesions;

Treatment options

1. Tumours raised above the skin
   • - excision with 0.5cm margin
2. Tumours not raised above the skin
   • wider margin of excision, particularly if inner canthus of eye, nasolabial fold, nasal floor and ear - may need frozen section to ensure adequate excision