Risk Factors of Schwartz et al for a Positive Sentinel Lymph Node in a Patient with a Merkel Cell Carcinoma

 

Parameters:

(1) tumor thickness in mm, from 0 to 25 mm

(2) pattern of growth, either circumscribed or infiltrative

 

A sentinel lymph node is more likely to show a metastasis if:

(1) the tumor shows an infiltrative growth pattern

(2) the tumor thickness is greater

 

For a tumor with infiltrative growth pattern, the probability of sentinel lymph node metastases is:

 

probability =

= (-0.1071 * ((tumor thickness in mm)^2)) + (5.376 * (tumor thickness)) + 31.36

 

For a tumor with circumscribed growth pattern, the probability of sentinel lymph node metastases is:

Tumor Thickness	Probability of Sentinel Lymph Node Metastases
0 to 10 mm	(0.05 * ((tumor thickness in mm)^2)) + (3.31 * (tumor thickness)) + 15.55
10 to 25 mm	(-0.14 * ((tumor thickness in mm)^2)) + (7.62 * (tumor thickness)) - 7.1
> 25 mm	> 98%

from Figure 1 page 1039

 

Additional risk factors:

(1) high mitotic rate per square mm (> 30 per square meter)

(2) increasing clinical size (>= 1 cm in diameter)