Basal Cell Carcinoma

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Introduction & Risk Factors - The Sun's Kiss

  • Most common human malignancy; locally invasive, slow-growing tumor.
  • Origin: Basal layer of epidermis or hair follicles. Low metastatic potential.
  • Primary Risk Factors:
    • UV Radiation: Chronic sun exposure (UVB > UVA), history of sunburns.
    • Phenotype: Fair skin (Fitzpatrick I-II), light hair/eyes.
    • Age: Typically > 40 years.
    • Genetics: Gorlin syndrome (NBCCS), Xeroderma Pigmentosum (XP).
    • Immunosuppression (e.g., organ transplant recipients).
    • Others: Ionizing radiation, arsenic, prior BCC. Skin Cancer: Genetics and Risk Factors

⭐ BCC constitutes approximately 80% of all non-melanoma skin cancers (NMSC).

Pathogenesis (Hedgehog) - Hedgehog's Hijack

Hedgehog pathway in normal and mutated BCC cells

  • Core: Uncontrolled Hedgehog (Hh) pathway.
  • "Hedgehog's Hijack":
    • Normal: SHH ligand binds PTCH1 (receptor); PTCH1's inhibition of SMO (transducer) is lifted → GLI activation → controlled growth.
    • BCC (UV-induced mutations):
      • PTCH1 (tumor suppressor) Loss-of-Function (LoF, ~90%): Fails to inhibit SMO.
      • SMO (oncogene) Gain-of-Function (GoF, ~10%): Constitutively active.
    • Outcome: Constitutive SMO activation → ↑GLI activity → uncontrolled proliferation.
  • Gorlin Syndrome: Germline PTCH1 mutation.

⭐ UV-induced PTCH1 mutations are key in most sporadic BCCs.

Clinical Types & Sites - The Many Masks

  • Nodular (~60%): Most common. Pearly papule/nodule, telangiectasias, rolled border. Central ulcer (rodent ulcer). Site: Head/neck (esp. nose).
  • Superficial (~30%): Erythematous, scaly plaque; thread-like border. Site: Trunk, shoulders.
  • Morpheaform/Sclerosing (~5-10%): Waxy, scar-like plaque; ill-defined. Aggressive, ↑recurrence. Site: Mid-face.
  • Pigmented: Brown/black pigment in any type. Mimics melanoma.
  • Fibroepithelioma of Pinkus (FEP): Rare. Firm, pink papule. Site: Lumbosacral.
  • Sites: >80% head & neck (sun-exposed). Nose most common.

    ⭐ Nodular BCC: most common type; pearly papule with telangiectasias, often on nose. oka

Diagnosis & Histology - Clues in Cells

  • Dermoscopy (ELM): Key diagnostic aid.
    • Arborizing (branching) telangiectasias.
    • Blue-gray globules/ovoid nests.
    • Spoke-wheel areas, leaf-like structures.
    • Shiny white structures (chrysalis).
    • Ulceration.
  • Skin Biopsy: Essential for confirmation (shave, punch, excisional).
  • Histopathology (H&E stain): 📌 BCC = Blue Cells, Clefts, Palisading.
    • Tumor islands of basaloid cells (blue): scant cytoplasm, hyperchromatic nuclei.
    • Peripheral palisading: columnar cells at nest periphery align.
    • Stromal retraction (clefts): artifactual spaces around tumor islands.
    • Mucinous stroma.

    ⭐ Peripheral palisading of nuclei and peritumoral stromal retraction are pathognomonic histological hallmarks of BCC. Basal Cell Carcinoma Histopathology

Treatment & Prognosis - Erase & Chase

Mohs surgery steps

  • Surgical (Gold Standard):
    • Excision: 3-5 mm margins (low-risk).
    • Mohs Micrographic Surgery (MMS): Highest cure, tissue sparing. For H-zone, recurrent, large, aggressive.
    • Curettage & Electrodessication (C&E): Small, superficial, low-risk.
  • Non-Surgical:
    • Topical: Imiquimod, 5-FU (superficial BCC).
    • Radiotherapy (RT): Adjuvant/primary if surgery contraindicated.
    • Systemic: Vismodegib, Sonidegib for advanced/metastatic.
  • Prognosis: Excellent (>95% 5-yr cure). Recurrence ↑ with aggressive subtypes, perineural invasion.

⭐ Mohs Micrographic Surgery offers the highest cure rates (up to 99%) and best tissue conservation, vital for facial BCCs.

High‑Yield Points - ⚡ Biggest Takeaways

  • Most common human malignancy, linked to chronic sun (UVB) exposure.
  • Slow, local invasion is characteristic; metastasis is extremely rare.
  • Classic: pearly papule/nodule with telangiectasias, rolled borders, and central ulceration (rodent ulcer).
  • Histo: nests of basaloid cells, peripheral palisading, and stromal retraction.
  • Affects sun-exposed areas (face, neck); nose is a very common site.
  • Nodular BCC is the most frequent subtype.
  • Multiple early BCCs suggest Gorlin syndrome.

Practice Questions: Basal Cell Carcinoma

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Which of the following is NOT a feature of Peutz-Jeghers syndrome?

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Flashcards: Basal Cell Carcinoma

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_____ surgery involves sequential horizontal excision of the BCC with immediate pathologic margin assessment.

TAP TO REVEAL ANSWER

_____ surgery involves sequential horizontal excision of the BCC with immediate pathologic margin assessment.

Mohs micrographic

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