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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 reproductable
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.
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