Classification of isolated tumor cells: Clarification of the 6th edition of the american joint committee on cancer staging manual

In May 2002, the 6th edition of the American Joint Committee on Cancer (AJCC) Cancer Staging Manual was published, and the new staging system was officially adopted for use in tumor registries in January 2003. The changes adopted for the chapter concerning breast carcinoma were the result of recommendations made by a task force comprising internationally recognized experts in the field of breast carcinoma management. This task force was charged with proposing changes that reflected published clinical data and current clinical consensus. Although the breast carcinoma staging system presented in the 6th edition includes much-needed changes reflecting contemporary standards of care, it is undeniably more complex than the system presented in previous editions of the staging manual. This is especially true of the new material dealing with the distinction between isolated tumor cells and micrometastases. With the increasing use of sentinel lymph node biopsy, immunohistochemical (IHC) staining, and molecular biologic techniques, pathologists can more easily detect microscopic lesions at the level of isolated tumor cells. We do not yet know whether these isolated cells have any clinical significance, and the accrual of relevant data has been hindered by the lack of a clear quantitative distinction between isolated tumor cells and micrometastases. The 6th edition of the AJCC Cancer Staging Manual has made this distinction based on size; isolated tumor cells are defined as metastatic lesions no larger than 0.2 mm in dimension and classified as pN0, whereas micrometastases are defined as metastatic lesions larger than 0.2 mm in dimension but no larger than 2.0 mm in dimension and classified as pN1mi. The AJCC Cancer Staging Manual is an evolving document. Even as one revision is published, new information is coming to light that will ultimately mandate the need for future editions. Since the publication of the 6th edition, task force members have fielded a large 2740