Basal Cell Carcinoma Flashcards
What is basal cell carcinoma (BCC)?
A slow-growing, locally invasive skin cancer arising from the basal layer of the epidermis, and the most common type of skin cancer.
Which population is most commonly affected by BCC?
Fair-skinned individuals, particularly those with chronic sun exposure, and people over 50 years of age.
What are the major risk factors for BCC?
Chronic ultraviolet (UV) light exposure.
Fair skin, light hair, and blue/green eyes.
Older age.
History of sunburns.
Immunosuppression (e.g., organ transplant recipients).
Genetic conditions (e.g., Gorlin syndrome).
What is the underlying cause of BCC?
Mutations in the hedgehog signaling pathway, most commonly involving the PTCH1 gene, leading to uncontrolled cell growth in the basal layer of the epidermis.
How does UV exposure contribute to BCC?
UV radiation induces DNA damage, including mutations in tumor suppressor genes like TP53.
What are the common clinical subtypes of BCC?
Nodular BCC: Most common; pearly papule with telangiectasia and central ulceration.
Superficial BCC: Erythematous, scaly plaques with rolled edges, often on the trunk.
Morpheaform (sclerosing) BCC: Scar-like, indurated lesion with ill-defined borders.
Pigmented BCC: Similar to nodular but with increased melanin, resembling melanoma.
What is the most common site for BCC?
Sun-exposed areas, particularly the face (e.g., nose, periorbital region).
What is the “rodent ulcer” appearance in BCC?
A central ulceration with rolled, pearly edges, often seen in advanced nodular BCC.
How is BCC diagnosed?
Clinical examination: Characteristic appearance and history.
Skin biopsy: Confirms the diagnosis; types include shave, punch, or excisional biopsy.
What histological features are seen in BCC?
Basaloid cells with peripheral palisading.
Tumor nests within the dermis.
Stromal retraction artifact.
What are the main treatment options for BCC?
Surgical excision: Gold standard for most cases, with histological margin assessment.
Mohs micrographic surgery: Preferred for high-risk or cosmetically sensitive areas (e.g., face).
Curettage and electrodesiccation: For small, low-risk lesions.
Cryotherapy: An option for small, superficial lesions.
Topical therapies: Imiquimod or 5-fluorouracil for superficial BCCs.
Radiation therapy: For inoperable cases or elderly patients.
Targeted therapy: Vismodegib or sonidegib (hedgehog pathway inhibitors) for advanced or metastatic BCC.
What is the Hedgehog (Hh) signaling pathway?
A key pathway in embryonic development that regulates cell differentiation, proliferation, and tissue patterning.
Is the Hedgehog pathway active in normal adult cells?
It is usually inactive in most adult tissues but may remain active in hair follicles and stem cells.
How is the Hedgehog pathway regulated in normal cells?
Sonic Hedgehog (Shh) binds to the PTCH1 receptor, relieving its inhibition of SMO (Smoothened).
SMO activation leads to downstream signaling and activation of transcription factors like GLI1 and GLI2, which promote target gene expression.
How does the Hedgehog pathway contribute to BCC?
Mutations in the Hedgehog pathway lead to its aberrant activation, driving uncontrolled proliferation of basal cells.
