Basal Cell Carcinoma
Most common human cancer; slow-growing locally invasive tumor of basal keratinocytes driven by UV-induced PTCH/Hedgehog mutations.
Also known as: BCC, basal cell carcinoma, rodent ulcer, nodular BCC, morpheaform BCC
Overview
The most common cutaneous malignancy, arising from basal keratinocytes of the epidermis and hair follicle. Slow-growing, locally invasive, and rarely metastatic.
Epidemiology
Most common cancer in humans worldwide. ~4 million US cases annually. Lifetime risk ~30% in fair-skinned individuals. Male > female (2:1). Median age at diagnosis ~70, but incidence rising in younger adults.
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Risk factors
- Chronic and intermittent UV exposure (UVB > UVA); cumulative lifetime exposure most important
- Fair skin (Fitzpatrick I-II), light hair and eyes
- Ionizing radiation (childhood radiation therapy)
- Immunosuppression (organ transplant — 10x risk; HIV; chronic immunosuppressants)
- Arsenic exposure (drinking water in some regions; multiple BCCs and superficial palmar/plantar keratoses)
- Genetic syndromes: basal cell nevus (Gorlin) syndrome — PTCH1 mutation; xeroderma pigmentosum; Bazex-Dupré-Christol; Rombo syndrome
- Personal history of skin cancer (40% develop second BCC within 5 years)
Pathophysiology
UV radiation induces mutations in PTCH1 (most common, ~70%), SMO, and SUFU components of the Hedgehog signaling pathway → constitutive Hedgehog activation → GLI transcription factor activation → uncontrolled basaloid proliferation. p53 mutations also common. Slow growth and intact stromal interactions limit metastatic potential (<0.05%).
Clinical presentation
Symptoms
- Often asymptomatic; patient notices 'pimple' or 'sore that won't heal' for months to years
- Occasional bleeding with minor trauma; rarely painful unless ulcerated/infected
Signs / physical exam
- Nodular BCC (most common, ~60%): pearly translucent papule or nodule with rolled border, arborizing telangiectasias, and central depression or ulceration ('rodent ulcer')
- Superficial BCC (~30%): erythematous scaly slightly elevated patch with thread-like rolled border; trunk/extremities; can mimic eczema/psoriasis
- Pigmented BCC: nodular BCC with brown/blue-gray pigment; common in skin of color
- Morpheaform (sclerosing/infiltrative) BCC: ill-defined indurated white-yellow scar-like plaque; high recurrence; subclinical extension
- Basosquamous: aggressive variant with mixed histology
- Distribution: 80% on head/neck (especially nose, ears, eyelids, lips); less commonly trunk and extremities
Classic findings
Pearly translucent nodule with rolled border, telangiectasias, and central ulcer on a sun-exposed area of an older fair-skinned adult.
Differential diagnosis
- Squamous cell carcinoma — Hyperkeratotic, scaly, ulcerated, more rapid growth; sun-damaged background
- Melanoma (amelanotic / nodular) — Pink or pigmented nodule; biopsy mandatory
- Sebaceous hyperplasia — Yellow-pink lobulated papule with central umbilication; benign
- Intradermal melanocytic nevus — Soft skin-colored papule, stable over years
- Molluscum contagiosum — Smooth umbilicated papules, multiple, children/immunocompromised
- Trichoepithelioma / fibrofolliculoma — Familial multiple small papules on face; biopsy
- Microcystic adnexal carcinoma — Indurated yellowish-pink plaque, slow growth on face; deeply invasive
- Bowen disease (SCC in situ) — Erythematous scaly plaque, slow growth
Diagnostic workup
Diagnostic criteria
Histopathologic confirmation of basaloid tumor cells in palisading nests with retraction artifact and myxoid stroma.
Labs
- Tissue diagnosis required — skin biopsy (shave or punch)
- Histopathology subtype determines management (nodular, superficial, morpheaform/infiltrative, basosquamous, micronodular)
Imaging
- CT/MRI only for advanced or recurrent tumors with suspected perineural invasion or deep tissue involvement
- Routine imaging not indicated for typical primary BCC
Diagnostic algorithm
| Subtype | Appearance | Preferred Treatment |
|---|---|---|
| Nodular (60%) | Pearly papule, rolled border, telangiectasias, central ulcer | Surgical excision 4 mm margin; Mohs if H-zone |
| Superficial (30%) | Erythematous scaly patch with thread-like rolled border | Imiquimod, 5-FU, ED&C, or excision |
| Pigmented | Nodular BCC with brown/blue-gray pigment | Excision; Mohs if H-zone |
| Morpheaform / infiltrative | Ill-defined scar-like indurated plaque | Mohs preferred — subclinical extension common |
| Basosquamous (aggressive) | Variable; mixed BCC + SCC histology | Mohs ± radiation; consider systemic for advanced |
| Locally advanced / metastatic | Deep invasion or unresectable | Vismodegib / sonidegib; cemiplimab if HPi-resistant |
Treatment
First-line
- Surgical excision with 4 mm margins for low-risk primary BCC (cure rate ~95%)
- Mohs micrographic surgery (preferred for high-risk BCC): face (especially H-zone — central face, periocular, periauricular, perinasal), morpheaform/infiltrative subtypes, recurrent tumors, large tumors (>2 cm), positive margins after standard excision — cure rate ~99% for primary, ~95% for recurrent
- Electrodessication and curettage (ED&C) for low-risk superficial or small nodular BCC on trunk/extremities (NOT on terminal hair-bearing skin or face — high recurrence)
- Topical therapy for superficial BCC: imiquimod 5% cream 5x/week × 6 weeks OR 5-fluorouracil 5% cream BID × 3-6 weeks — cure rates 70-90%
- Cryotherapy with liquid nitrogen for superficial BCC in selected patients
- Photodynamic therapy for superficial BCC (cosmetic advantage)
- Radiation therapy for non-surgical candidates or as adjuvant
Locally advanced / metastatic BCC
- Hedgehog pathway inhibitors: vismodegib 150 mg daily, sonidegib 200 mg daily — for laBCC or mBCC not amenable to surgery/radiation
- Adverse effects: muscle spasms, dysgeusia, alopecia, weight loss, teratogenicity (strict contraception)
- Cemiplimab (anti-PD-1) — FDA-approved for laBCC after Hedgehog inhibitor failure
Basal cell nevus (Gorlin) syndrome
- Multidisciplinary surveillance starting in childhood
- Limit UV and radiation exposure (avoid CT when possible)
- Vismodegib for tumor burden reduction
- Genetic counseling for family members
Second-line / adjunct
- Annual to biannual total body skin examination — 40% develop second BCC within 5 years
- Sun protection counseling: broad-spectrum SPF ≥30 daily, sun-protective clothing, hat, sunglasses, shade
- Vitamin D supplementation as appropriate (avoid recommending sun exposure for vitamin D)
Complications
- Local tissue destruction — 'rodent ulcer' can erode cartilage, bone, eye, brain in neglected cases
- Cosmetic/functional disfigurement, especially on face
- Recurrence (lifetime ~50% develop another skin cancer)
- Rare metastasis (<0.05%) — usually basosquamous or morpheaform subtypes
- Hedgehog inhibitor adverse effects and resistance over time
PANCE pearls
- Pearly translucent papule + rolled border + arborizing telangiectasias + central ulcer = nodular BCC.
- Morpheaform BCC looks like a scar without history of injury — biopsy any new 'scar' on sun-damaged skin.
- ED&C should NEVER be used on the face or hair-bearing scalp — high recurrence.
- Imiquimod and 5-FU are excellent options for superficial BCC on trunk/extremities, but expect significant inflammation during treatment.
- Hedgehog pathway inhibitors (vismodegib, sonidegib) revolutionized therapy for advanced BCC — particularly impactful in Gorlin syndrome.
References
- NCCN 2024 — NCCN Clinical Practice Guidelines in Oncology — Basal Cell Skin Cancer (Version 1.2024)
- AAD 2018 — Guidelines of Care for the Management of Basal Cell Carcinoma (Kim et al., J Am Acad Dermatol 2018)
- USPSTF 2023 — USPSTF Recommendation: Screening for Skin Cancer (JAMA 2023)
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