A mathematical model of axillary lymph node involvement considering lymph node size in patients with breast cancer

Surgical sampling for assessing axillary status has not been considered as a well defined surgical procedure. We have reported that MRI is a good instrument for assessing lymph node size and identifying lymph node position. We also developed a mathematical model that takes into consideration the size of axillary lymph nodes, and retrospectively determined the number and size of the axillary lymph nodes that need to be sampled from level I-II to achieve a greater than 90% probability of metastasis detection after surgical sampling, with the future aim of using MR-axillography to assess lymph node size.

One thousand nine hundred and thirty four lymph nodes from 102 level I-II dissections performed on T1 and T2 breast cancer patients with nodal metastases were examined histologically and the greatest long-axis dimension on histologic slides was measured.

This model permitted determination of the cutoff level necessary for an expected probability of detection of metastasis of over 90%. The cutoff level, regardless of tumor size, is a maximum of 6 nodes removed from level I-II in which the greatest long-axis measurement is greater than or equal to 6 mm. The cutoff level in patients with macrometastatic nodes is a maximum of 3 or 4 nodes in which the long-axis dimensions are greater than or equal to 9 or 7 mm, respectively, removed from level I-II.

This model showed that surgical sampling on the basis of lymph node size might have good potential to detect lymph nodes metastases.