Breslow and Clark classifications of melanoma invasion

16. What are the Breslow and Clark classifications of melanoma invasion?
Clark selected five levels of melanoma
thickness in the skin:

• Level I-intradermal melanoma that does not
  metastasize; may be better termed atypical melanotic hyperplasia: a benign lesion
• Level II-melanoma that penetrates the basement membrane into the papillary dermis
• Level III-melanoma that fills the papillary dermis and encroaches on the reticular dermis in a pushing fashion
• Level IV-melanoma that invades the reticular dermis
• Level V-melanoma that works its way into the
  subcutaneous fat

The Breslow method requires an optical micrometer fitted to the ocular position of a standard microscope. This technique is a more exact determination of tumor invasion. Lesions are classified as follows:

• ≤ 0.75 mm
• 0.76-1.5 mm
• 1.51-3.99 mm
• ≥ 4.0 mm

Lesions < 1 mm include melanoma in situ and thin invasive tumors.
The cure rate in the latter is over 95% with excision. Tumors of 1.0-4.0 mm are called intermediate but involve risk of metastasis.
Lesions > 4.0 mm are high-risk lesions with a poor cure rate. All melanomas should be checked by both methods because some tumors may show a low Breslow measurement with a deeper Clark level, indicating a great risk of recurrence and spread. Measurement of thickness is important, and the tumor should be measured from the total height of the lesion vertically at the point of maximal thickness. In addition, if ulceration is present, the measurement should be from the bottom of the ulcer crater down to the deepest margin of the lesion.