ypN

ypN refers to a staging descriptor used in cancer classification systems, specifically within the TNM (Tumor, Node, Metastasis) staging system. The 'N' in TNM stands for lymph nodes, and the 'p' prefix indicates that the staging information is based on pathological examination of resected tissue, as opposed to clinical assessment. Therefore, ypN describes the extent of cancer involvement in regional lymph nodes that has been assessed after neoadjuvant therapy, which is treatment given before surgery. Neoadjuvant therapy, such as chemotherapy or radiation, is administered with the goal of shrinking the tumor and potentially affecting lymph node metastases before surgical removal.

The ypN staging uses a numerical system to categorize the number and location of involved lymph nodes. For example, ypN0 indicates no cancer is found in the regional lymph nodes. Higher ypN numbers, such as ypN1, ypN2, or ypN3, signify increasing numbers of positive lymph nodes and/or more extensive involvement. The specific criteria for each ypN category are defined by the staging manual, most commonly the American Joint Committee on Cancer (AJCC) Cancer Staging Manual. This pathological staging after neoadjuvant treatment is crucial for determining the prognosis of the patient and guiding further treatment decisions.