Nonmelanoma Skin Cancers


Basal Cell Carcinoma (BCCA)

  1. Epidemiology
    • most common skin cancer
    • exposure to UV radiation is the most common risk factor
    • 90% have a mutation in the hedgehog signaling pathway
    • significant occupational hazard for people with outdoor occupations
    • more common in people with fair complexions

  2. Clinical Appearance
    • several different morphologies:

    1. Nodular BCCA
      • most common type (70%)
      • waxy, cream-colored lesion with rolled borders
      • often contains a central ulcer (“rodent ulcer”)

      Nodular Basal Cell Cancer
    2. Pigmented BCCA
      • tan to black in color
      • must be distinguished by biopsy from melanoma

      Pigmented Basal Cell Cancer
    3. Superficial BCCA
      • red, scaly lesion with irregular, ill-defined margins
      • may be mistaken for psoriasis or eczema
      • usually found on the trunk

      Superficial Basal Cell Cancer
  3. Clinical Course
    • usually slow growing
    • often neglected for years
    • metastasis and death are extremely rare
    • can cause extensive local destruction

  4. Risk of Recurrence
    • BCCAs can be classifies as low risk or high risk for recurrence

    1. Low Risk
      • lesions < 10 mm on the cheek, forehead, scalp, neck
      • lesions < 20 mm on the trunk and extremities
      • well-defined borders
      • no history of immunosuppression or radiation treatment at the site

    2. High Risk
      • lesions >= 10 mm on the face or >= 20 mm on the trunk and extremities
      • recurrent lesions
      • history of immunosuppression or radiation
      • perineural or vascular invasion

  5. Treatment
    1. Surgical Excision
      • 4 – 6 mm margins are adequate for low-risk lesions
      • high-risk lesions require 10 mm margins
      • primary closure is usually possible

    2. Mohs Micrographic Surgery
      • used for low-risk lesions on cosmetically sensitive areas of the face (eyelids, nose)
      • involves serially excising the lesion with immediate frozen-section examination of all the margins
      • major drawbacks are cost and the length of time involved (up to several days), since complete excision may require multiple attempts
      • cure rates are comparable to wide excision

    3. Topical Treatments
      • usually offered to patients who prefer to avoid excision
      • imiquimod or topical 5-fluoruracil are associated with higher recurrence rates than surgery

    4. Field Therapy
      • treats a generalized area
      • margins cannot be evaluated
      • many options are available: cryotherapy, radiation therapy, electrodessication and curettage, and photodynamic therapy

Squamous Cell Carcinoma (SCCA)

  1. Epidemiology
    • second most common skin cancer
    • risk factors include sun exposure, chemical carcinogens, previous radiation, chronic inflammation (burn scars, chronic osteomyelitis) and chronic immunosuppression
    • after organ transplantation, there is a 65 times increased risk of developing a SCCA
    • invasive SCCAs may metastasize to regional lymph nodes or distant sites

  2. Biologic Behavior
    • may spread both vertically and horizontally

    1. Tumor Thickness
      • correlates well with biologic behavior
      • lesions that recur locally are usually more than 4 mm thick
      • lesions that metastasize are usually more than 10 mm thick

    2. Tumor Size
      • tumors less than 2 cm in diameter have recurrence rates of 5% and a 7% incidence of metastasis
      • tumors greater than 2 cm have twice the local recurrence rate and three times the incidence of regional lymphatic spread

    3. Tumor Location
      • tumors arising in burn scars, areas of chronic osteomyelitis, and areas of previous injury metastasize early
      • lesions on the external ear frequently recur and involve regional nodes early

  3. Clinical Appearance
    • scaly lesions that become ulcerated centrally and have elevated, firm edges
    • may be confused with keratoacanthoma

    Squamous Cell Skin Cancerr
  4. Treatment
    1. Primary Lesion
      • small lesions may be treated with curettage/electrodessication, cryotherapy, or topical agents
      • most low-risk lesions should be surgically excised with a 4 – 6 mm margin
      • high-risk lesions will require a 1 cm margin
      • Mohs surgery is indicated for lesions that require a tissue-sparing approach (eyelid, nose)

    2. Regional Nodes
      • a SLN biopsy is indicated in high-risk patients with clinically negative nodes
      • a node dissection is indicated for clinically palpable nodes
      • a prophylactic node dissection is indicated for lesions arising in chronic wounds

Merkel Cell Carcinoma (MCC)

  1. Epidemiology
    • rare, aggressive cutaneous malignancy with a high risk of recurrence and metastasis
    • primary affects older adults with fair skin
    • has a predilection for sun-exposed areas
    • more frequent in immunosuppressed patients

  2. Pathogenesis
    • neuroendocrine tumor that may originate from Merkel cells, which are located in the basal layer of the epidermis and hair follicles
    • Merkel cell polyomavirus has been causally linked to the development of MCC in 60% - 80% of patients

  3. Clinical Manifestations
    • most present as a fast growing, firm, flesh-colored or reddish-colored, intracutaneous nodule
    • majority are located on the head and neck, upper arms, and shoulders
    • 26% of patients have regional node involvement, and 8% already have distant metastases at the time of diagnosis

    Merkel Cell Cancer
  4. Management
    1. Primary Tumor
      • wide local excision with 1 - 2 cm margins
      • adjuvant XRT, especially for head and neck lesions or close margins

    2. Regional Lymph Nodes
      1. Clinically Negative Nodes
        • SLN biopsy since occult nodal disease is found in 33% of patients
        • completion node dissection and adjuvant XRT is indicated for a positive SLN

      2. Clinically Positive Nodes
        • requires FNA or core needle biopsy confirmation
        • complete metastatic work up
        • regional node dissection followed by adjuvant XRT if the metastatic workup is negative

    3. Adjuvant Therapy
      • no evidence to support adjuvant chemotherapy or immunotherapy, although these agents have value in metastatic disease







References

  1. Sabiston, 20th ed., pgs 747 – 750
  2. UpToDate. Treatment and Prognosis of Basal Cell Carcinoma at Low Risk of Recurrence. Sumaira Z. Aasi, MD. July 22, 2020. Pgs 1 – 39
  3. UpToDate. Treatment and Prognosis of Low-risk Cutaneous Squamous Cell Carcinoma. Sumaira Z. Aasi, MD, Angela M. Hong, MBBS, MMed, PhD. Oct 28, 2020. Pgs 1 – 41
  4. UpToDate. Pathogenesis, Clinical Features, and Diagnosis of Merkel Cell (Neuroendocrine) Carcinoma. Patricia Tai, MB, BS, DABR, FRCR, FRCPC, Paul T Nghiem, MD, PhD, Song Youn Park, MD. Aug 13, 2020. Pgs 1 – 25
  5. UpToDate. Staging and Treatment of Merkel Cell Carcinoma. Patricia Tai, MB, BS, DABR, FRCR, FRCPC, Song Youn Park, MD, Paul T Nghiem, MD, PhD, July 15, 2019. Pgs 1 – 25