Squamous Cell Carcinoma

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SCC Basics - Sunny Side Scourge

  • Malignant tumor of epidermal keratinocytes, often showing keratinization (keratin pearls).
  • Second most common skin cancer (after BCC); higher metastatic potential than BCC.
  • Key Risk Factors:
    • Sun Exposure: Chronic UVB > UVA. Main cause for cutaneous SCC.
    • Immunosuppression: Organ transplant recipients (↑65-250x risk), HIV.
    • Chronic Inflammation: Scars (Marjolin's ulcer), chronic ulcers, sinuses (e.g., osteomyelitis).
    • HPV: Esp. types 16, 18 (anogenital, periungual, oral SCC).
    • Chemicals: Arsenic, tar, soot.
    • Radiation: Ionizing radiation.
    • Genetic: Xeroderma Pigmentosum (XP), Albinism, Epidermolysis Bullosa.
    • Precursors: Actinic keratosis (AK), Bowen's disease (SCC in situ), Leukoplakia.

⭐ UVB radiation (290-320 nm) is the most implicated etiological factor for cutaneous SCC, primarily through formation of pyrimidine dimers.

Early squamous cell carcinoma on sun-exposed skinoka

Clinical Canvas - Spot the Suspect

  • Presentation: Firm, indurated papules, plaques, or nodules; often scaly, crusted, ulcerated, or hyperkeratotic. Friable, bleeds easily.
    • Common sites: Sun-exposed skin (face, ears, lower lip, hands), mucous membranes.
  • Key Variants:
    • SCC in situ (Bowen's Disease): Well-defined, erythematous, scaly patch/plaque. Non-invasive.
      • Genital variant: Erythroplasia of Queyrat.
    • Keratoacanthoma (KA): Rapidly growing, dome-shaped nodule with central keratin plug. "Crateriform."
    • Marjolin's Ulcer:

      Marjolin's ulcer, an SCC arising in chronic wounds, burns, or scars (e.g., chronic osteomyelitis sinus tracts), is often more aggressive and has a higher metastatic potential.

  • Symptoms: Often asymptomatic; may be tender or pruritic. Perineural invasion (PNI) can cause pain, paresthesia.

Microscopic Clues & Staging - Deep Dive Diagnosis

  • Biopsy is Gold Standard: Confirms SCC.
    • Histopathology (HPE):
      • Atypical squamous cells: Invasive cords/nests.
      • Keratin pearls (📌 "Onion rings").
      • Intercellular bridges (desmosomes).
      • Cellular pleomorphism, hyperchromasia, ↑mitotic activity.
      • Grading: Well, moderately, poorly differentiated.

    ⭐ Histopathologically, SCC is characterized by invasive cords and nests of atypical squamous epithelial cells with features like keratin pearls, intercellular bridges, and varying degrees of differentiation.

  • Staging (AJCC TNM 8th Ed.): Guides prognosis & treatment.
    • T (Tumor): Size & invasion depth.
      • T1: ≤ 2 cm. T2: >2-4 cm. T3: >4 cm/PNI/deep invasion. T4: Bone/skull base.
    • N (Nodes): Regional lymph node spread.
      • N1: Single ipsilateral ≤ 3 cm.
    • M (Metastasis): Distant spread.
      • M1: Present.

Histopathology of Squamous Cell Carcinoma

Treatment Tactics - Eradication Roadmap

  • Risk Stratification: Guides therapy (Low vs. High-risk).
  • Surgical (Primary):
    • Excision: Margins 4-6 mm (low-risk), 6-10 mm (high-risk).
    • Curettage & Electrodessication (C&E): Small, low-risk.
    • Cryosurgery: Superficial, low-risk.

    ⭐ Mohs Micrographic Surgery (MMS) is the treatment of choice for high-risk SCCs (e.g., large size, aggressive histology, recurrent, critical anatomical sites like face/ears/hands) due to its high cure rate and maximal tissue conservation.

  • Non-Surgical:
    • Radiotherapy (RT): Primary or adjuvant.
    • Topical: 5-Fluorouracil (5-FU), Imiquimod (SCC in situ/Bowen's).
  • Advanced/Metastatic: Systemic (Immunotherapy, Chemotherapy, EGFR inhibitors).
  • Adjuvant: RT for high-risk features (PNI, +margins).
  • Prevention: Sun protection, skin checks.

Mohs surgery procedure steps

High‑Yield Points - ⚡ Biggest Takeaways

  • Second most common skin cancer, arises from epidermal keratinocytes.
  • Major risk: Chronic sun exposure (UVB). Others: immunosuppression, HPV, chronic scars (Marjolin's ulcer), arsenic.
  • Precursors: Actinic keratosis, Bowen's disease (SCC in situ).
  • Clinically: Indurated, scaly, crusted, or ulcerated lesion, often bleeds easily.
  • Higher metastatic risk than BCC; lip/ear lesions, perineural invasion, and immunosuppression are high-risk factors.
  • Diagnosis: Full-thickness biopsy. Treatment: Surgical excision; Mohs for high-risk lesions.

Practice Questions: Squamous Cell Carcinoma

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Mohs micrographic excision for basal cell carcinoma is used for all the following Except

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Flashcards: Squamous Cell Carcinoma

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_____ is an intraepidermal squamous cell carcinoma is characterized by a persistent, non elevated, red, scaly or crusted plaque

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_____ is an intraepidermal squamous cell carcinoma is characterized by a persistent, non elevated, red, scaly or crusted plaque

Bowen s disease

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