A semiquantitative grading scheme was developed for describing the histologic changes of pulmonary asbestosis. This can be used to compare patients and can help determine the role of asbestosis in a variety of complications. The scheme was presented by a special committee of the College of American Pathologists (CAP) and the U.S. National Institute for Occupational Safety and Health (NIOSH).
Histologic examination:
(1) Up to 5 lung lobes are examined (right upper, right middle, right lower, left upper, left lower)
(2) Usually 2-4 histologic blocks are prepared from each lobe (left upper 4 blocks, left lower 3 blocks, right upper 3 blocks, right middle 2 blocks, right lower 3 blocks; as shown in Figure 38 on page 590).
Parameters:
(1) grade for severity of fibrosis
(2) grade for the extent of fibrosis
|
Parameter |
Finding |
Grade |
Points |
|
severity |
no fibrosis is associated with bronchioles |
0 |
0 |
|
|
fibrosis involves the wall of at least 1 bronchiole with or without extension into the septa of the immediately adjacent layer of alveoli; no fibrosis is seen in more distant alveoli |
1 |
1 |
|
|
Grade 1 plus fibrosis involves alveolar ducts or >= 2 layers of adjacent alveoli; there is a zone of nonfibrotic alveolar septae between adjacent bronchioles |
2 |
2 |
|
|
Grade 2 plus coalescence of fibrotic change; all alveoli between at least 2 adjacent bronchioles have thickened, fibrotic septa; some alveoli may be completely obliterated |
3 |
3 |
|
|
Grade 3 plus formation of spaces that are larger than alveoli, ranging up to 1 cm in diameter (honeycombing); the spaces may or may not be lined by epithelium |
4 |
4 |
|
extent |
only occasional bronchioles involved; most show no lesion |
A |
1 |
|
|
more than occasional involvement but less than half of all bronchioles involved |
B |
2 |
|
|
more than half of all bronchioles involved |
C |
3 |
score for each lobe =
= (severity grade) * (numerical value for extent grade)
where:
• In the example given in Table 1 (page 593), if multiple slides were examined from a lobe, then separate scores were given for each slide and the score for the lobe for the lung was the average for the slides examined.
• However, since the severity grade is based on the most severe lesion on a slide, there would be an argument that the most severe grade in all of the slides from the lobe should be used.
total score =
= SUM(scores for all lobes evaluated)
final grade =
= (total score) / (number of lobes examined)
Interpretation:
• minimum score for a lobe: 0
• maximum score for a lobe: 12
Specialty: Toxicology, Emergency Medicine, Critical Care
