Micrometastasis

Micrometastases are defined by the UICC TNM Classification of Malignant Tumors as conglomerations of tumor cells measuring between 0.2 mm and 2 mm in size. Clusters of cells sized less than 0.2 mm in maximal dimension are termed isolated tumor cells (ITCs). Tumor clusters measuring larger than 2 mm are macrometastases, usually just called metastases . Although the official staging manuals tend to concentrate on micrometastases in lymphatic tissue, it can be applied to any tissue, e.g. liver .

These definitions are necessarily histopathological in scope, as in practical terms micrometastases refers to cancers that cannot be visualized on any diagnostic imaging study.