Clark's level is a staging system, which describes the level of anatomical invasion of the melanoma in the skin. It was developed by Wallace H. Clark Jr. at Harvard University and Massachusetts General Hospital in the 1960s.
Levels Five anatomical levels are recognized, and higher levels have worsening prognostic implications. These levels are: Level 1: Melanoma confined to the epidermis (melanoma in situ) Level 2: Invasion into the papillary dermis Level 3: Invasion to the junction of the papillary and reticular dermis Level 4: Invasion into the reticular dermis Level 5: Invasion into subcutaneous tissue.
National usage In the United States, the current staging system adopted by the American Joint Committee on Cancer (AJCC) no longer considers Clark's level, because it is less prognostic and more subjective than other alternatives.
However, it is a mandatory component for melanoma pathology in Sweden.
See also Staging of melanomas Breslow's depth
References
Sources Melanoma Staging Systems. National Cancer Institute. A resource on Clark's levels and Breslow's depth. Original article from Breslow. Cancer res, 1969.