Figure 2. Modeled volume calculations for lymph node metastatic invasion.

Using mathematical modeling based on spherical volumes, it was determined that within a 1 cm lymph node, the transition between micrometastasis and macrometastasis occurs when the metastasis occupies 0.8% of the total volume of the lymph node (2 mm diameter). Structures larger than 0.8% of the total volume are considered macrometastasis (illustrated in orange), while structures between 0.8% and 0.008% are considered to be in the micrometastasis range (illustrated in blue). Isolated tumor cell (ITC) clusters occupy a volume of less than 0.008% of the lymph node.