These small lymph nodes adjacent to vessels are too small for detection by physical examination or by imaging techniques. However, one node contains metastatic adenocarcinoma. This is an example of micrometastases. The terms micrometastasis, isolated tumor cell (ITC), and circulating tumor cell (CTC) have been applied to spread of cancer not easily detectable. They may be detected by microscopy, aided by immunohistochemistry, but sampling is an issue. They illustrate the pathogenesis of spread of malignant neoplasms, but their importance for staging is difficult to determine. With the TNM staging system, the N category includes pN1(mi) for micrometastases and pN0(i+) for ITCs. Therapy must be individualized. [Image courtesy of Jinping Li MD PhD, Mercer University]
