Clark level

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The Clark level is a histological system used to classify the stages of malignant melanoma . A microscopic examination is carried out in the surgically removed cancerous tissue and the surrounding healthy skin areas to determine how far the deepest still detectable tumor tissue is from the skin surface. One therefore speaks of the penetration depth according to Clark .

For the Clark level, the size of the superficial spread of the tumor or its volume is irrelevant. However, it gives an indication of how far different layers of the skin are already affected. Since the spread of a skin tumor essentially depends on whether it is able to reach deeper layers with lymph and blood vessels , the Clark level represents a prognostic factor in order to be able to decide on a further therapeutic approach.

  • Clark level I: All tumor cells are located above the basement membrane (corresponds to a melanoma in situ )
  • Clark level II: crossing of the basement membrane, invasion of the papillary layer ( stratum papillare ) of the dermis .
  • Clark level III: Invasion to the limit of the reticulate layer ( stratum reticulare ) of the dermis.
  • Clark Level IV: Invasion of the Network Layer
  • Clark Level V: Invasion into the subcutaneous tissue

The Clark level is usually given together with other classification systems, such as the tumor thickness according to Breslow and the TNM classification .

The Clark level is named after the US dermatologist Wallace H. Clark jr. (1924–1997) who published this assessment scheme for malignant melanoma in 1969.

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  • WH Clark Jr., L. From, EA Bernardino et al .: The Histogenesis and Biologic Behavior of Primary Human Malignant Melanomas of the Skin . Cancer Research (1969) 29: pp. 705-727, PMID 5773814 ( pdf )
  • CM Balch et al .: A multifactorial analysis of melanoma: prognostic histopathological features comparing Clark's and Breslow's staging methods . Ann. Surg. (1978) 188 (6): pp. 732-742, PMID 736651 , PMC 1397001 (free full text)