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Melanoma Staging Schemes

Malignant melanoma is an example of a site where several staging schemes with prognostic significance have been developed based on a different histologic and clinical criteria. Each has been shown to be a valid method of staging disease at this site.

Clark's Level of Invasion

History:

Proposed by WH Clark, et al, in 1969. Showed that the risk of nodal metastases could be directly related to the depth of penetration of the tumor.

Criteria:

Histologic classification based on resection of entire lesion.

Restrictions:

  • Does not take nodal involvement into consideration; deals only with primary tumor.
  • Uniformity of staging not always reproducible because of variations in the depth of layers of the skin.
  • Cannot be applied accurately to melanomas of the palms and soles.
  • Histologic difference between growth patterns of superficial spreading and nodular malignant melanomas.

Categories:

Level I: Confined to epidermis (in situ); never metastasizes; 100% cure rate Level II: Invasion into papillary dermis; invasion past basement membrane (localized) Level III: Tumor filling papillary dermis (localized), and compressing the reticular dermis Level IV: Invasion of reticular dermis (localized) Level V: Invasion of subcutaneous tissue (regionalized by direct extension)

Guidelines for Clark's Levels:

  • The most difficult differentiation is between Level II and Level III.
  • Level I is technically non-existent (in-situ melanoma has other names).
  • If there is involvement of lymph nodes or distant metastases, another staging system must be used.
  • Examination of entire tumor is important in order to accurately assess the level of invasion.

Breslow's Depth of Invasion

History:

Proposed by A. Breslow in 1970.

Criteria:

Pathologic staging based on measurement of tumor invasion of dermis using the micrometer on the microscope. More reproducible system than Clark's Levels.

Categories:

  • Actual measurement of depth of lesion is recorded Example: lesion measures 0.8 mm
  • Cases are grouped for study as follows:
    • 0.75 mm (comparable to Clark Level II)
    • > 0.75 - 1.5 mm (comparable to Clark Level III)
    • > 1.5 - 4.0 mm (comparable to Clark Level IV)
    • > 4.0 mm (comparable to Clark Level V)

Guidelines for using Breslow's system:

  • Record measurement in abstract. If both Clark's and Breslow's stages are given, record both.
  • If there is involvement of lymph nodes or distant metastases, another staging system must be used.
  • Examination of entire tumor is important in order to accurately assess the level of invasion.

Clinical Staging for Malignant Melanoma

  • Used for staging of melanomas which have spread beyond the primary tumor or which do not have adequate tissue for pathological examination.
  • Clinical staging includes results of tests and examinations as well as pathological findings.
  • Clinical staging parallels Summary Staging
    • Stage I Localized—without metastases to distant or regional nodes (allows localized disease up to 5 cm. from initial tumor within primary lymphatic drainage area
    • Stage II Regionalized—involvement of regional nodes
    • Stage III Disseminated—visceral or lymphatic metastases or multiple cutaneous or subsequent metastases
  • Reference to stage in melanoma cannot be assumed to be clinical, Clark's, or Breslow's unless specifically identified as such.