Basal Cell Carcinoma Subtypes and Treatment
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Direct answer
Basal cell carcinoma is the most common skin cancer in fair-skinned people, a locally invasive tumour of basaloid cells that seldom metastasises. It arises mainly on sun-exposed skin and is driven by activation of the hedgehog pathway, most often through PTCH1 loss or SMO change. Excision with clear margins cures most lesions, with Mohs surgery reserved for high-risk sites and aggressive subtypes.
What you must remember
- Nodular: the commonest subtype, a pearly papule with a rolled edge, telangiectasia and central ulceration that gives the classic rodent ulcer.
- Superficial: an erythematous, scaly patch on the trunk that is often multiple and responds well to topical therapy.
- Morphoeic (sclerosing): an ill-defined, scar-like plaque with indistinct borders, high recurrence and subclinical spread, so Mohs surgery is preferred.
- Pigmented: a nodular tumour with melanin that can mimic melanoma and needs dermoscopy and biopsy.
- Gene basis: PTCH1 loss or SMO activation in the hedgehog pathway; naevoid basal cell carcinoma (Gorlin) syndrome is caused by germline PTCH1 mutation.
- Metastasis: rare, and mainly seen in large, neglected, long-standing or recurrent tumours.
- Advanced disease: vismodegib and sonidegib are hedgehog inhibitors reserved for unresectable locally advanced or metastatic BCC.
Subtypes compared and matched to treatment
Subtype predicts behaviour and the choice of treatment, so read the clinical description and dermoscopy together. The table compares the usual subtypes with their preferred management.
| Subtype | Clinical clue | Behaviour | Usual treatment |
|---|---|---|---|
| Nodular | Pearly papule, rolled border, telangiectasia | Slow, local | Excision, or curettage with cautery |
| Superficial | Scaly erythematous patch on trunk | Superficial, often multifocal | Imiquimod, 5-fluorouracil or PDT |
| Morphoeic | Ill-defined sclerotic plaque | Infiltrative, high recurrence | Mohs surgery |
| Pigmented | Brown to black nodule | Behaves like nodular, may mimic melanoma | Excision after biopsy |
Morphoeic and infiltrating types have ill-defined borders, so clinical clearance is unreliable and margin control is needed. Primary low-risk lesions are usually excised with a margin of about 4 mm, and histology remains the reference for subtype and clearance.
Where the subtype questions catch candidates
Most basal cell carcinoma questions test subtype recognition and the choice between excision and Mohs surgery.
- Trap: choosing Mohs surgery for every basal cell carcinoma. Correct: low-risk nodular lesions at low-risk sites usually respond to standard excision, and Mohs is reserved for high-risk sites and subtypes.
- Trap: calling a pigmented BCC a melanoma without biopsy. Correct: dermoscopy shows leaf-like areas, blue-grey ovoid nests and arborising vessels, but biopsy settles the diagnosis.
- Trap: using hedgehog inhibitors first line for a small nodular BCC. Correct: they are for unresectable or metastatic disease, and they are teratogenic.
Frequently asked questions
Which basal cell carcinoma subtype is the most common?
Nodular basal cell carcinoma is the most common subtype, presenting as a pearly papule with telangiectasia and a rolled border. It grows slowly, and central ulceration gives the classic rodent ulcer appearance.
When is Mohs surgery preferred for basal cell carcinoma?
Mohs micrographic surgery is preferred for morphoeic, infiltrative and recurrent basal cell carcinomas, and for tumours in high-risk areas such as the central face. It offers tissue sparing and complete margin control on frozen sections.
What is the role of hedgehog inhibitors in basal cell carcinoma?
Hedgehog inhibitors such as vismodegib and sonidegib are reserved for locally advanced or metastatic basal cell carcinoma that cannot be treated with surgery or radiotherapy. Common adverse effects include muscle cramps, alopecia and dysgeusia, and they are teratogenic.
Which gene change causes naevoid basal cell carcinoma syndrome?
Naevoid basal cell carcinoma syndrome, also called Gorlin syndrome, is caused by germline PTCH1 mutations. It produces multiple basal cell carcinomas, jaw keratocysts and palmar pits, and sporadic basal cell carcinoma also involves hedgehog pathway activation.
Can superficial basal cell carcinoma be treated without surgery?
Yes, superficial basal cell carcinoma can be treated with imiquimod, 5-fluorouracil or photodynamic therapy, provided the diagnosis is confirmed by biopsy. Recurrence is more likely with topical treatment than with excision, so follow-up is essential.