Prognostic Model of Clark et al for Stage I Malignant Melanoma

 

Stage I melanoma:

(1) pT1: tumor 0.75 mm or less in thickness and invading the papillary dermis (Clark Level II)

(2) pT2: tumor more than 0.75 mm in thickness but not more than 1.5 mm in thickness and/or invades to the papillary-reticular interface (Clark Level III)

 

Algorithm Steps

 

(1) Determine that the lesion is invasive malignant melanoma.

(2) Search the sections for the thickest part of the tumor and measure the thickness in millimeters using Breslow's method.

(3) Assign the Clark level of invasion.

(4) Tumors over 0.76 mm in thickness are, with rare exceptions, in the vertical growth phase. Clark Level III and IV tumors are usually in vertical growth phase.

(5) Examine tumors less than 0.76 mm thick and showing Clark Level II invasion for the cellular arrangement that distinguishes between the radial and vertical growth phases. A radial only growth phase may be seen with in situ tumors (pTis) or with invasive "nontumorigenic" melanomas.

(6) Determine the mitotic rate of tumors in the vertical growth phase.

(7) Evaluate the degree of tumor infiltration by lymphocytes for tumors in the vertical growth phase.

(8) If the tumor is in the vertical growth phase, determine the presence or absence of regression anywhere in the tumor.

(9) Record the anatomic site of the primary tumor and the sex of the patient.

(10) If the tumor is only in the radial growth phase, the projected survival probability is 100%

(11) If the tumor is in the vertical growth phase, calculate the projected survival probability.

 

Calculating the Survival If Vertical Growth Phase Present

 

Vertical growth is present, then assess the following variables:

(1) mitotic rate per square millimeter (variables V1 and V2)

(2) tumor-infiltrating lymphocytes (variables V3 and V4)

(3) tumor thickness (variable V5)

(4) anatomic site (variable V6)

(5) sex of the patient (variable V7)

(6) histologic regression (variable V8)

 

see Table 4, Clark 1989, page 1897

 

survival factor =

= (-3.07) + (2.46 * V1) + (1.25 * V2) + (2.43 * V3) + (1.26 * V4) + (1.40 * V5) + (1.33 * V6) + (1.07 * V7) + (1.03 * V8)

 

probability of survival at 8 years =

= 1 / (1 + (e ^ (-1 * (survival factor))))