Skin melanocytic tumor
Clark levels of invasion

Author: Christopher Hale, M.D.

Revised: 20 August 2018, last major update May 2013

Copyright: (c) 2002-2018,, Inc.

PubMed Search: Clark's levels invasion

Page views in 2018: 4,523
Page views in 2019 to date: 283
Cite this page: Hale, C.S. Clark levels of invasion. website. Accessed January 23rd, 2019.
Definition / general
  • I: not penetrating basement membrane (in situ)
  • II: in papillary dermis (difficult to differentiate II versus III, SEER)
  • III: filling and expanding the papillary dermis and stopping at the interphase between the papillary and reticular dermis
  • IV: in the reticular dermis
  • V: in the subcutaneous tissue
  • References: Cancer 2000;88:589
Diagrams / tables

Images hosted on other servers:

Clark levels

Uses by pathologists
  • First described by Clark in 1969 (Cancer Res 1969;29:705); defines subcategories of T1 melanomas (1 mm or less in thickness, J Natl Cancer Inst 1989;81:1893)
  • Identification of higher risk thin melanomas should be based on Breslow depth, not Clark level IV (Cancer 2001;91:983)
  • Clark levels are related to incidence of nodal metastases but only consider primary tumor, not nodes or metastases
  • Less prognostic significance than T classification (J Craniofac Surg 2007;18:1353)
  • Less reproducible than Breslow system (J Pathol 1991;163:245); also not always uniform due to variation in depth of skin layers
  • 8 year disease free survival is 96.3% with level II, 76.1% with level III, 60.7% with level IV and 38.5% with level V (J Natl Cancer Inst 1989;81:1893)
  • Must recognize that deep collection of malignant melanocytes may be attached to a pilosebaceous unit
Additional references