Comparison of the 1980 - 2000 versions of the ILO Classification
There are a number of important changes between the 1980 and the 2000 versions of the ILO Classification, which are primarily related to the recording of pleural abnormalities.
Classification of small and large pneumoconiotic opacities has not changed with the 2000 revision
The ILO 2000 clarifies procedures for recognition and measurement of pleural shadows:
A minimum width of about 3mm is required for pleural change to be recorded as present, with the measurement from the inner margin of the rib to the sharp margin of the plaque against the lung parenchyma. Recording categories of width are optional for both localized and diffuse pleural thickening, and are not required unless specified.
Extent of chest wall plaque or diffuse pleural thickening is based on the combined lengths of the en face and in profile pleural thickening
If calcification is seen in the pleura, then a plaque must be recorded as present. Site must be indicated, but quantification of the extent of calcification is no longer recorded
Costophrenic angle (CPA) obliteration may occur with or without diffuse pleural thickening. However, diffuse pleural thickening cannot occur without CPA obliteration; width categories for diffuse pleural thickening are similar to plaque, and are not required unless specified.
New symbols:
aa - atherosclerotic aorta
at - significant apical pleural thickening
cg - calcification in non-pneumoconiotic opacities (granulomata) or lymph nodes
me - mesothelioma
pa - plate atelectasis
pb - parenchymal bands
ra - rounded atelectasis
Clarification
ax - symbol to be indicated when the margins of small opacities are still visible, and can be used in the presence or absence of large opacities
ca - any thoracic cancer, aside from mesothelioma
di - marked distortion of any one intrathoracic structure is sufficient for this symbol
ih - ill defined heart should be marked if a length equal to 1/3 of the left heart border is involved, but this could be on either the right or the left heart border
pi - no longer is mediastinal pleural thickening included in this symbol
tb - this symbol is used for suspected tuberculosis either active or inactive, but not a calcified primary complex, which should be coded as cg