Basal cell carcinoma (BCC) is the most common keratinocyte cancer—and the most prevalent skin cancer overall. Sometimes called rodent ulcer or basalioma, BCC often presents as multiple primary tumours over a patient’s lifetime. Risk increases with age and cumulative ultraviolet exposure, and is classically higher in older men, though women and younger adults are also affected. Additional risk factors include a personal history of BCC or other skin cancers such as squamous cell carcinoma and melanoma; signs of chronic sun damage such as photoaging and actinic keratoses; and a history of blistering sunburns. Individuals with fair skin, blue eyes, and blond or red hair are at higher risk, although BCC can arise in all skin types. Prior skin injuries and thermal burns, certain inflammatory dermatoses (for example, cutaneous lupus) and congenital lesions such as sebaceous naevus, as well as inherited syndromes including basal cell naevus (Gorlin) syndrome, Bazex–Dupré–Christol syndrome, Rombo syndrome, Oley syndrome, and xeroderma pigmentosum, further elevate risk. Ionizing radiation, arsenic exposure, immune suppression from disease or medications, and some drugs such as hydrochlorothiazide have also been implicated.
BCC arises through multifactorial pathways, most notably ultraviolet-induced DNA damage involving the PTCH tumour-suppressor gene within the hedgehog signalling pathway. Both spontaneous and inherited defects can predispose to tumour formation. Clinically, BCC is a locally invasive tumour that typically appears as a slowly enlarging plaque or nodule that may be skin-coloured, pink, or pigmented. Lesions can bleed or ulcerate spontaneously. Although BCC rarely threatens life, a subset may grow rapidly, invade deeply, or, very rarely, metastasize to regional lymph nodes.
Several clinical subtypes are recognised, with more than 20 histologic growth patterns. Nodular BCC, the most common facial subtype, presents as a shiny, pearly papule or nodule with surface telangiectasia and often a central depression or ulcer, creating a rolled border; cystic lesions feel soft with jelly-like contents. Micronodular, microcystic, and infiltrative patterns behave more aggressively. Superficial BCC, seen more often on the upper trunk and shoulders of younger adults, manifests as a thin, slightly scaly erythematous plaque with a translucent rolled edge and multiple micro-erosions. Morphoeic (sclerosing) BCC, typically on mid-facial sites, resembles a waxy, scar-like plaque with indistinct borders and may show perineural involvement. Basosquamous carcinoma demonstrates mixed BCC and SCC features and tends to be more aggressive.
Recurrence after treatment is not unusual, particularly when excision margins are narrow or incomplete, or when high-risk histologies such as morphoeic, micronodular, or infiltrative patterns are involved, especially on the head and neck. Advanced BCCs are often large, neglected tumours with deep invasion that may be challenging or unsuitable for surgery. Metastatic BCC is exceptionally rare and typically arises from large, recurrent, or aggressive primary tumours that have undergone multiple prior treatments.
Diagnosis is often made clinically based on a characteristic, slowly enlarging lesion and confirmed histologically by biopsy or following excision. Selected superficial BCCs on the trunk and limbs may be managed non-surgically based on a confident clinical diagnosis, although histologic confirmation is preferred when the diagnosis is uncertain or when high-risk features are present.
Centre for Medical and Surgical Dermatology, in Pickering led by board-certified Dermatologist Dr. Breslavets, provides comprehensive BCC diagnosis, treatment, and surveillance. Care plans are individualised to tumour type, size, location, histology, and patient factors, and may include biopsy, surgical excision, and coordinated long-term dermatologic follow-up to reduce recurrence risk and detect new lesions early.
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