Originally used to describe foci of metastatic cells measuring less than 2 mm.
Tumor in lymph nodes less than 0.2 mm defined as isolated tumor cells.
Now signifies metastases detected by whatever means provided that they were not seen during routine histopathologic examination.
In breast, colorectal, gastric, gallbladder, lung and esophageal cancers associated with increased risk of systemic recurrence and reduced survival implying such metastases are an indicator of aggressive tumor biology.
The 21 gene recurrence score, revealing low risk in patients with micrometastasis, found there is no benefit in chemoendocrine therapy in overall survival.