Basal cell carcinoma
- Lesion
The commonest cancer of all. It grows slowly on sun-exposed skin and almost never spreads, but it can destroy local tissue.
What it is
Basal cell carcinoma is the most frequent invasive cancer in people with fair skin. It arises on sun-exposed skin, especially the face, and is driven by constitutive activation of the Hedgehog pathway, most often through loss of PTCH1 or activation of SMO. It invades locally and can be very destructive (rodent ulcer), but metastasis is rare.
Structure
- Nests and cords of basaloid cells with scant cytoplasm, palisaded nuclei at the periphery.
- Clefts (retraction) between tumour and mucinous stroma.
- Superficial: buds from the epidermis; morpheaform: thin strands in dense fibrous stroma.
- Pigmented variants can mimic melanoma clinically.
Step by step
- Sonic hedgehog normally binds PTCH1, releasing its inhibition of SMO.
- Loss of PTCH1 (UV-induced or germline) or activating SMO mutation lets SMO signal without ligand.
- GLI transcription factors move to the nucleus and switch on growth genes.
- Basal keratinocyte-like cells proliferate as nests that invade the dermis.
- Growth is local and slow; the tumour depends on its stroma, so metastasis is rare.
Clinical notes
- Treated by excision; Mohs surgery for the face and ill-defined subtypes.
- Risk factors: UV, fair skin, ionising radiation, arsenic, immunosuppression, xeroderma pigmentosum.
Test yourself
Think of the answer, then tap the question to see it.
Which pathway is activated in basal cell carcinoma?
The Hedgehog pathway, usually by loss of PTCH1 or activating SMO mutation.
What are the histologic hallmarks of basal cell carcinoma?
Nests of basaloid cells with peripheral palisading and retraction clefts from a mucinous stroma.
Which features define Gorlin syndrome?
Germline PTCH1 mutation with multiple early basal cell carcinomas, jaw keratocysts, palmar pits and risk of medulloblastoma.
Elsewhere in DurgiPedia
- Radiation and cancer: ultraviolet and ionizing
- Tumour suppressor genes: RB, TP53, APC, BRCA and the two-hit hypothesis
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Skin Cancer Treatment (PDQ®)–Health Professional Version (National Cancer Institute, 2025); Gorlin syndrome (MedlinePlus, US National Library of Medicine, 2025).
Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake
Representative model, for educational purposes only.