Basal Cell Carcinoma and Squamous Cell Carcinoma Study Notes

Overview of Skin Cancers

  • Focus on basal cell carcinoma (BCC) and squamous cell carcinoma (SCC)

  • Learning Objective: Describe risk factors, pathophysiology, and clinical manifestations of BCC and SCC

Classification of Skin Cancers

  • Skin cancers classified into two categories:

    • Non melanoma skin cancers (NMSC): 70% BCC, 30% SCC

    • Melanoma skin cancer

Pathophysiology of Skin Cancers

  • Common factor: High levels of UV light exposure

    • **BCC Specific Factors:

    • Chemical exposure

    • SCC Specific Factors:

    • Human Papillomavirus (HPV) infection

    • Melanoma Specific Factors:

    • Familial gene mutation (inherited mutations)

Cellular Origins of Skin Cancers

  • Cell Types Affected:

    • Basal Cell Carcinoma (BCC): DNA mutation in stratum basale cells (stem cells)

    • Squamous Cell Carcinoma (SCC): DNA mutation in epidermal keratinocytes

  • Key concept: Disordered replication leads to DNA mutations, resulting in dysplasia and eventual neoplasia

Differences Between BCC and SCC

  • Aggressiveness:

    • BCC – least aggressive

    • SCC – more aggressive, potential to metastasize

  • Skin Lesions: Both types present as skin lesions

Basal Cell Carcinoma (BCC)

  • Definition: Most common skin tumor (70% of NMSCs)

  • Anatomy & Growth Patterns:

    • Occurs in sun-exposed skin, predominantly on the head and neck

    • Grows slowly and rarely metastasizes

    • Visible Types:

    • Superficial:

      • Morphology: Red, defined lesions, macular, sometimes pearly appearance

    • Nodular:

      • Morphology: Translucent papule or nodule, possible small dilated vessels, sometimes ulcerated and bled

    • Morphoeic:

      • Morphology: Pale, sclerotic lesion, waxy/white/yellowish, invasive, requires aggressive treatment

  • Pathophysiology Details:

    • Initiated by excessive UV exposure, leading to DNA damage of pluripotent stem cells

    • Role of Tumor Suppressor Genes:

    • Approximately 50% of BCCs involve mutations in tumor suppressor genes, obstructing DNA repair and apoptosis

  • Common Risk Factors:

    • Light skin, red hair, blue eyes, freckles, older age

  • Clinical Features/Manifestations:

    • Elevated nodule with central depression, possible tissue destruction (less than a rodent ulcer)

  • Diagnosis Methods:

    • Observation and biopsy to confirm BCC

  • Management Tactics:

    • Surgical excision, particularly challenging for morphoeic types due to undefined borders

Squamous Cell Carcinoma (SCC)

  • Definition: Invasive malignant tumor arise from stratum spinosum epithelial cells

  • Development: Often preceded by actinic keratosis (thickened, scaly patches due to UV exposure)

  • Key Risk Factors:

    • Primary factor: Sun exposure

    • HPV infection (certain strains)

    • Immunosuppression, vitamin D deficiency

  • Etiology:

    • Risk factors that may also contribute to tumor initiation

    • Actinic keratosis can progress to SCC but not all do

    • Gene mutations (tumor suppressor genes p53, notch1, notch2, RAS)

    • HPV plays a role in 25% of SCC cases, inhibiting DNA repair and promoting survival of mutated cells

  • Pathophysiology Details:

    • Excessive UV exposure causes alterations in keratinocyte signaling, leading to oxidative stress and subsequent mutations

  • Clinical Features/Manifestations:

    • Persistent non-healing ulcer, scaly crust, possible bleeding, localized invasion

  • Diagnosis Methods:

    • Biopsy to distinguish SCC from other forms of skin cancer (BCC, melanoma)

  • Management Tactics:

    • Surgical excision usually performed in outpatient settings; may also require radiation or chemotherapy based on patient history and biopsy results

Conclusion

  • Understanding risk factors, pathophysiology, and clinical manifestations of BCC and SCC is crucial for effective diagnosis and management.