Musculoskeletal & Dermatologic Pathologies › Common Skin Lesions

Common Skin Cancers

Notes

Common Skin Cancers

Sections






Overview

Here, we'll learn about common skin cancers and benign neoplasms.
For reference, a "neoplasm" is an abnormal growth that can be either benign or malignant (cancerous).

We'll divide these neoplasms into pigmented and nonpigmented lesions.

Benign Pigmented Lesions

Moles (Nevi)

Normal Mole

  • Normal moles are small, well-defined benign growths: a brown-colored circular lesion.
  • It is symmetric in color, has a regular border, an even color, is typically less than 6 mm in diameter, and does not evolve (all of which are the opposite of malignant melanoma).

Atypical Moles

  • These are less well defined than normal moles and serve as a warning that the patient has the potential to develop melanoma. It is very rare for the mole, itself, to convert to a melanoma (but rather is a harbinger that the patient is more prone to develop melanoma).
  • Atypical moles are symmetric in color, have irregular borders (rather than a regular one), color variegation (mixtures of reds, shades of brown, etc…) (rather than even color), but they are still typically less than 6 mm in diameter, and do not typically evolve.

Blue Nevus

  • Blue nevus is, as its name states, a darkly-blue pigmented mole, a benign growth (despite its worrisome coloration).

Additional Benign, Pigmented Neoplasms

Freckles

  • Freckles are activated by UV-sunlight.
  • Ephelis refers to those that fade without ongoing sunlight (in the dark months).
  • Lentigo refers to those that persist in the dark months. Other characteristics that distinguish these, as well.

Seborrheic keratosis

  • Seborrheic keratoses are benign, beige-brown papules and plaques that have a "stuck-on" appearance (we'll re-visit them when we discuss squamous cell carcinoma).

Cancerous Pigmented Lesions

Malignant Melanoma

Melanoma Overview

  • Malignant melanoma has the highest skin cancer-related mortality (is the leading cause of death due to skin cancer). It is commonly cited as the 5th most common type of cancer in the US (but pay attention that this does not include squamous cell and basal cell carcinomas, however).

Subtypes of Melanoma

There are multiple types of melanoma:

  • Superficial spreading melanoma (~ 65%)
  • Acral-lentiginous melanoma (on the palms and soles (the plantar distal extremities) and underneath the nails (subungal), which account for ~ 75% of melanomas in blacks and ~ 50% in Asians.
  • Nodular melanoma, the 2nd most common type of melanoma, overall.
  • Lentigo maligna, in sun-damaged areas

Uncommon melanoma variants:

  • Amelanotic melanoma
  • Spitzoid melanoma
  • Desmplastic melanoma
  • Pigment synthesizing (animal-type) melanoma (aka, melanocytoma)

Melanoma Characteristics (ABCDE criteria)

  • Melanoma can be asymmetric and possess drastically different coloration on two sides; it can possess a highly irregular border; color variegation – zones of different colors; is typically greater than 6 mm; and it evolves over time. For reference, the median growth rate for a superficial spreading melanoma is ~ 0.12 mm per month. Rate of growth in melanomas: characteristics and associations of rapidly growing melanomas.
  • Another consideration is is the ugly duckling sign, which means, if a mole stands out from the other of a patient's typical moles, have a higher suspicion of melanoma.
  • The Glasgow 7-point checklist is a useful scoring system that can help guide melanoma evaluation.
  • With melanoma evaluation, "When in doubt, refer it out!" to a dermatologist – they having imaging modalities and can biopsy when necessary.

Morbidity/Mortality

  • Malignant melanoma has a high propensity for metastasis. Fortunately, ~ 95% of melanomas are identified prior to distant metastasis, however, when melanoma does metastasize, it can do so widely.
  • Common distant sites (beyond the skin and regional subcutaneous tissue) are as follows:
    • Lungs
    • Liver (and other gastrointestinal organs, less commonly)
    • Bone
    • Central nervous system (brain, meninges, etc...)

Melanoma Staging (TNM)

  • Primary Tumor (T)
    • Thickness.
      From 0 (no identifiable primary tumor)
      to 4 (> 4 mm).
    • Ulceration status.
      a for NO ulceration.
      b for ulceration.
    • Example, T2a would be a 1 to 2 mm thickness primary tumor with NO ulceration.
  • Regional lymph node involvement (N)
    • Number of nodes.
      0 for no regional lymph node metastasis.
      Up to 3 for two or more nodes detected.
      There is also an a, b, or c scoring for further scoring of lymphatic metastasis.
  • Distant Metastasis (M)
    • Anatomic site.
      0 for no distant metastasis.
      1, then a, b, c, d based on specific site:
      a for regional dermatologic/musculoskeletal
      b for lung
      c for NON-CNS visceral
      d for CNS sites
    • LDH level.
      0 for NOT elevated LDH level.
      1 for elevated LDH level.
    • Example, M1a(1) would be local metastasis with an elevated LDH level.

Benign NON-Pigmented Lesions

Benign NON-Pigmented Lesions

Epidermal inclusion cysts

  • Epidermal inclusion cysts are common benign cysts with a pore (a punctum or comedone).

Actinic keratosis

  • Actinic keratoses are crusty papules or plaques. Notably, they are potentially squamous cell carcinoma precursors.

Cancerous NON-Pigmented Lesions

squamous cell carcinoma

Overview

Morphology

  • Squamous cell carcinoma are irregularly-shaped; are pinkish in hue, are plaques (meaning they are elevated), and have characteristic hemorrhagic crusts (scabs).

Key Clinical Features

  • Squamous cell carcinoma (SCC) is the 2nd most common skin cancer of all but is only rarely lethal.
  • It typically arises from sun-exposed areas, but also injured tissue (scar tissue).
  • Pay special attention for squamous cell carcinoma in immune-suppression/organ transplant patients, in which it can be much more aggressive (cancers (including basal cell carcinoma) are typically more common in immune-suppressed patients but SCC even more so).
  • It's highly treatable but can easily metastasize from certain sites (such as the ear).

Additional Considerations

  • Actinic keratosis is a SCC precursor.
  • Seborrheic keratosis is a SCC mimicker.

basal cell carcinoma

Overview

Morphology

  • Basal cell carcinoma has a concentric-shape papule (early-on) is a pearly-pinkish color; is shiny; has notable telangiectasias.

Key Clinical Features

  • Basal cell carcinoma is the most common skin cancer, but only rarely lethal (like SCC).
  • Like SCC, it typically arises from sun-exposed areas, but also injured tissue (scar tissue).
  • It is also highly treatable.
  • As noted above, basal cell is more common in transplant patients (but not to the extent that SCC is).
  • Basal cell carcinoma is known for its local destruction and high recurrence risk.

References

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