Staging System for Mediastinals Tumors. A Proposal

Abstract

The mediastinum is an anatomic compartment that frequently lodges tumors of different histology, given the diversity of organs and structures that either occupy it or go through it, in one or another direction. Since the chest cavity is so large, is not uncommon to see patients presenting with pretty big tumors, sometimes invading vital organs, complicating their clinical status, anesthetic management and needed surgical procedures. Currently a common staging system applicable to patients with mediastinal tumors does not exist; the size of the mass and its relationships to neighboring organs is described from the imaging studies. If a TNM like system existed for mediastinal tumors, treating physicians could communicate and asses a particular lesion better, follow its response to treatment and could best define a prognosis for the patients. Based on the TNM system we propose herein an staging system for mediastinal tumors, utilizing the letters: T/I/N/M. The letter T expresses the relationship of volume of tumor, with the volume of the continent chest cavity; these volumes may be easily obtained from the CT scanner depending on its software. Otherwise the perimeter of the mass is drawn in the axial cuts, which are several millimeters thick and its density range is read in Hounsfield units. The computer determines the total volume of tissue slices comprised between the established density limits, and that constitutes the tumor volume in cubic centimeters. The volume of the chest cavity is obtained from the volume of the lungs, which is given by the amount of air filling them. The sum of it plus the tumor volume will give the whole chest cavity volume. Dividing tumor volume by the total chest volume, gives the relationship or T. Since we all have heart, trachea and great vessels their volume is not computed. The letter I, implies invasion, and the invaded organ is mentioned, such as cava, aorta, etc. If its lumen is <50% compromised a letter a) is added and if >50% a letter b) The letter N, reflects involvement or not of lymph node, particularly in non lymphomatous growths and the letter M, the presence or abscense of metastatic deposits. Tumor staging can be determined according to a combination of letters, exhibiting the more advanced, a larger proportion of tumor volume, vital organ invasion, lymph node enlargement and the presence of metastasis.