Vollmer et al developed a statistical model to predict the probability of lymph node metastases shortly after the diagnosis of a primary cutaneous malignant melanoma. The authors are from Duke University in North Carolina.
Parameters used for model identified by logistic regression:
(1) thickness of tumor in mm
(2) ulceration
(3) primary site
Parameter
Finding
Points
thickness in mm
maximal vertical thickness
(mm)
ulceration
absent
0
present
1
primary site
acral
0
extremity, non-acral
1
head or trunk
0
E =
= (0.693 * (points for site)) + (0.559 * (points for ulcer)) + (0.414 * (points for thickness)) – 1.90
pretest probability for nodal metastasis =
= 1 / (1 + EXP((-1) * E))
If the lymph nodes are subsequently biopsied, then the pretest probability and the histologic diagnosis can be used to estimate patient survival.
Pretest Probability
Lymph Node Pathology
10 Year Survival
< 0.5
negative
80%
< 0.5
positive
40%
>= 0.5
negative
60%
>= 0.5
positive
25%
from Figures 2 and 3, page 878
To read more or access our algorithms and calculators, please log in or register.
