Pathology in Cutaneous Melanoma

  • An experienced dermatopathologist is an important member of the multidisciplinary melanoma team:
    • That contributes to the accurate diagnosis and staging of patients with melanoma
  • It is my practice to have outside biopsies reviewed by our pathology staff upon referral to confirm diagnosis
  • Although the pathologic analysis primarily consists of microscopic examination of hematoxylin- and eosin-stained tumor:
    • Several melanocytic cell markers may also be useful to confirm the diagnosis
    • Two antibodies that have been widely used in immunohistochemical evaluations are:
      • S-100 and HMB-45:
        • S-100 is expressed not only by more than 90% of melanomas:
          • But also by several other tumors and some normal tissues, including dendritic cells
        • In contrast, the monoclonal antibody HMB-45:
          • Is relatively specific (yet not as sensitive) for proliferative melanocytic cells and melanoma
          • It is therefore often used as a confirmatory stain when the diagnosis of melanoma is being considered
      • Anti–MART-1 staining has also been shown to be very useful in the diagnosis of melanoma
      • The major histomorphologic components that should be included in a primary melanoma pathology report include:
        • Breslow thickness
        • Ulceration status
        • Peripheral and deep margin status
        • Mitotic rate:
          • Using the dermal hot spot approach with units of mitoses per mm2
        • Other features that are often also recorded include:
          • Presence of microsatellites
          • Histologic subtype
          • Lymphovascular invasion
          • Tumor-infiltrating lymphocytes (TIL)
          • Regression
          • Neurotropism
          • Growth phase
          • The absence of epidermal component:
            • As the latter may represent an uncommon dermal primary or a metastatic deposit
  • The major histomorphologic types of melanoma:
    • Superficial spreading melanomas:
      • Constitute the majority of melanomas:
        • Approximately 70% of melanomas
      • Generally arise in a pre-existing nevus
  • Nodular melanomas:
    • Are the second most common type:
      • 15% to 30% of melanoma
    • Nodular melanomas progress to invasiveness more quickly than other types:
      • However, when depth of the melanoma is controlled for:
        • Nodular melanomas are generally associated with the same prognosis as other lesions
  • Lentigo maligna melanomas:
    • Constitute a small percentage of melanomas:
      • 4% to 10%
    • These lesions occur in sun-exposed areas
    • Lentigo maligna melanomas are classically located on:
      • The faces of older white women
    • In general, lentigo maligna melanomas are:
      • Large (> 3 cm at diagnosis)
      • Flat lesions
      • Are uncommon in individuals younger than 50 years
    • Given their often-ill-defined appearance:
      • Margin control can sometimes be challenging at the time of wide excision
  • Acral lentiginous melanomas:
    • Occur on the palms (palmar), soles (plantar), or beneath the nail beds (subungual):
      • Although not all palmar, plantar, and subungual melanomas are acral lentiginous melanomas
    • These melanomas account for only 2% to 8% of melanomas in white patients but for a substantially higher proportion of melanomas (35% to 60%) in darker-skinned patients
    • They are often large:
      • With an average diameter of approximately 3 cm
  • Amelanotic melanomas:
    • Are relatively uncommon melanomas that occur without pigmentation changes
    • They are often more difficult to diagnose because of their lack of pigmentation
    • Factors such as:
      • Change in size
      • Asymmetry
      • Irregular borders may suggest malignancy and prompt a biopsy, but delays in diagnosis may sometimes be observed
  • While melanoma has been traditionally described using these categories:
    • Prognosis is more dependent upon staging than by these histomorphologic types

#Arrangoiz #CancerSurgeon #HeadandNeckSurgeon #SurgicalOncologist #Melanoma #SkinCancer #CASO #CenterforAdvancedSurgicalOncology

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s