Lymph node or lymphoid aggregate? Impact on cancer resection quality, clinical prognosis, and tumor staging

The clinical outcome of most cancer patients depends on the stage of the primary tumor, the lymph node status, and if distant metastases are present. According to the Union for International Cancer Control (UICC) and the American Joint Committee on Cancer (AJCC), the Tumor Node Metastasis (TNM) classification of malignant tumors requires the examination of a minimum number of regional lymph nodes for each type of cancer to fulfill the criteria of high-quality surgical oncology. Due to the daily challenge of collecting an appropriate number of lymph nodes and time constraints when processing and assessing tissue samples, pathologists may be tempted to identify every histological lymphoid structure mimicking a lymph node as a "true" lymph node. Faced with this issue, we propose to resolve it by specifying histological characteristics to differentiate lymphoid aggregates from "true" lymph nodes. To find a minimum consensus, we suggest defining as lymph nodes only those lymphoid structures composed of lymphoid cells encapsulated by a complete or incomplete fibrous capsule.