NCIt definition : A general term that refers to a TNM finding of cancer metastases usually in a limited
number of regional lymph nodes. The definition of N1a TNM finding depends on the specific
type of cancer that it refers to; for example, for breast cancer it refers to metastasis
in 1 to 3 axillary lymph nodes (at least 1 tumor deposit greater than 2.0 mm); for
cutaneous melanoma it refers to micrometastasis in one regional lymph node; for colorectal
cancer it refers to metastasis in one regional lymph node.;