Saturday, March 24, 2012

Updated: Thyroid Cancer Staging Guide

The stage of a cancer is a description (usually numbers I to IV with IV having more progression) of the extent the cancer has spread. The stage often takes into account the size of a tumor, how deeply it has penetrated, whether it has invaded adjacent organs, how many lymph nodes it has metastasized to (if any), and whether it has spread to distant organs. Staging of cancer is the most important predictor of survival, and cancer treatment is primarily determined by staging. Thus, staging does not change with progression of the disease as it is used to assess prognosis. 
A patients' cancer, however, may be re-staged after treatment but the staging established at diagnosis is rarely changed. Cancer staging can be divided into a clinical stage and a pathologic stage. In the TNM (Tumor, Node, Metastasis) system, clinical stage and pathologic stage are denoted by a small "c" or "p" before the stage (e.g., cT3N1M0 or pT2N0).
Because they use different criteria, clinical stage and pathologic stage often differ. Pathologic staging is usually considered the "better" or "truer" stage because it allows direct examination of the tumor and its spread, contrasted with clinical staging which is limited by the fact that the information is obtained by making indirect observations at a tumor which is still in the body. 
However, clinical staging and pathologic staging should complement each other. Not every tumor is treated surgically, therefore pathologic staging is not always available. Also, sometimes surgery is preceded by other treatments such as chemotherapy and radiation therapy which shrink the tumor, so the pathologic stage may underestimate the true stage. This staging system is used for most forms of cancer, except brain tumors and hematological malignancies
The American Joint Committee on Cancer (AJCC) created the following staging system for Thyroid Cancer Staging
  • T1 - Tumor diameter 2 cm or smaller
  • T2 - Primary tumor diameter greater than 2-4 cm
  • T3 - Primary tumor diameter greater than 4 cm limited to the thyroid or with minimal extrathyroidal extension
  • T4a - Tumor of any size extending beyond the thyroid capsule to invade subcutaneous soft tissues, larynx, trachea, esophagus, or recurrent laryngeal nerve
  • T4b - Tumor invades prevertebral fascia or encases carotid artery or mediastinal vessels
  • TX - Primary tumor size unknown, but without extrathyroidal invasion
  • NO - No metastatic nodes
  • N1a - Metastases to level VI (pretracheal, paratracheal, and prelaryngeal/Delphian lymph nodes)
  • N1b - Metastasis to unilateral, bilateral, contralateral cervical, or superior mediastinal mode metastases
  • NX - Nodes not assessed at surgery
  • MO - No distant metastases
  • M1 - Distant metastases
  • MX - Distant metastases not assessed
Stage I (any T, any N, M0)
Stage II (any T, any N, M1)

Author: Mark E Gerber, MD, FACS, FAAP  Clinical Assistant Professor of Otolaryngology, University of Chicago, Pritzker School of Medicine; Section Head, Pediatric Otolaryngology-Head and Neck Surgery, NorthShore University HealthSystem  

Co-Author: Brian Kip Reilly, MD  Assistant Professor of Otolaryngology and Pediatrics, Department of Otolaryngology, Children's National Medical Center, George Washington University School of Medicine

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