Pathology of asbestosis- An update of the diagnostic criteria: Report of the asbestosis committee of the college of american pathologists and pulmonary pathology society.

Asbestosis is defined as diffuse pulmonary fibrosis caused by the inhalation of excessive amounts of asbestos fibers. Pathologically, both pulmonary fibrosis of a particular pattern and evidence of excess asbestos in the lungs must be present. Clinically, the disease usually progresses slowly, with a typical latent period of more than 20 years from first exposure to onset of symptoms. DIFFERENTIAL DIAGNOSIS: IDIOPATHIC PULMONARY FIBROSIS: The pulmonary fibrosis of asbestosis is interstitial and has a basal subpleural distribution, similar to that seen in idiopathic pulmonary fibrosis, which is the principal differential diagnosis. However, there are differences between the 2 diseases apart from the presence or absence of asbestos. First, the interstitial fibrosis of asbestosis is accompanied by very little inflammation, which, although not marked, is better developed in idiopathic pulmonary fibrosis. Second, in keeping with the slow tempo of the disease, the fibroblastic foci that characterize idiopathic pulmonary fibrosis are infrequent in asbestosis. Third, asbestosis is almost always accompanied by mild fibrosis of the visceral pleura, a feature that is rare in idiopathic pulmonary fibrosis. DIFFERENTIAL DIAGNOSIS: RESPIRATORY BRONCHIOLITIS: Asbestosis is believed to start in the region of the respiratory bronchiole and gradually extends outward to involve more and more of the lung acinus, until the separate foci of fibrosis link, resulting in the characteristically diffuse pattern of the disease. These early stages of the disease are diagnostically problematic because similar centriacinar fibrosis is often seen in cigarette smokers and is characteristic of mixed-dust pneumoconiosis. Fibrosis limited to the walls of the bronchioles does not represent asbestosis. ROLE OF ASBESTOS BODIES: Histologic evidence of asbestos inhalation is provided by the identification of asbestos bodies either lying freely in the air spaces or embedded in the interstitial fibrosis. Asbestos bodies are distinguished from other ferruginous bodies by their thin, transparent core. Two or more asbestos bodies per square centimeter of a 5- mu m-thick lung section, in combination with interstitial fibrosis of the appropriate pattern, are indicative of asbestosis. Fewer asbestos bodies do not necessarily exclude a diagnosis of asbestosis, but evidence of excess asbestos would then require quantitative studies performed on lung digests. ROLE OF FIBER ANALYSIS: Quantification of asbestos load may be performed on lung digests or bronchoalveolar lavage material, employing either light microscopy, scanning electron microscopy, or transmission electron microscopy. Whichever technique is employed, the results are only dependable if the laboratory is well practiced in the method chosen, frequently performs such analyses, and the results are compared with those obtained by the same laboratory applying the same technique to a control population.

Pulmonary veno-occlusive disease and pulmonary capillary hemangiomatosis: a clinicopathologic study of 35 cases.

Pulmonary veno-occlusive disease (PVOD) and pulmonary capillary hemangiomatosis (PCH) are rare causes of pulmonary hypertension, regarded by some as distinct entities. However, their presentations are similar and both are associated with poor prognoses. We therefore reviewed 38 specimens [autopsies (n=15), surgical biopsies (n=15), explants (n=7), and pneumonectomy (1 case)] from 35 patients diagnosed as either PVOD (n=30; av. age 34 y, range 4 to 68 y; 19M:11F) or PCH (n=5, av. age 42 y, ranging from 9 months to 60 years; 3M:2F) to assess their interrelationship. PCH was identified in 24 (73%) cases diagnosed as PVOD, either as perivenular foci or diffuse involvement of the pulmonary parenchyma. Other features seen in PVOD were arterial medial hypertrophy and/or intimal fibrosis (88%), hemosiderosis (79%), venulitis (12%), infarction (9%), interstitial fibrosis (sometimes as localized scars) (48%), and a mild lymphocytic infiltrate (67%). In cases diagnosed as PCH, 4 showed venous and arterial changes of PVOD. Cases with PCH also all showed a mild interstitial lymphocytic infiltrate but there was no venulitis or infarction. Capillary proliferation was particularly well demonstrated by CD34 immunostaining and predominantly involved the alveoli, but was also seen within walls of bronchi and pulmonary vessels. Our data suggest that in the majority of cases PCH represents a secondary angioproliferative process caused by postcapillary obstruction rather than a separate disease. The cause of the venous obliteration was not identified but the occasional identification of phlebitis suggests this plays a role in venous damage in some cases.

An assessment of the expanded classification of congenital cystic adenomatoid malformations and their relationship to malignant transformation.

The purpose of this study was to review cases of congenital cystic adenomatoid malformations (CCAMs) arising in children and adults, in order to assess the recently expanded classification system for these lesions and their association with malignant transformation. Of 28 CCAMs, there were 16 type 1, 4 type 2, and 8 type 4 lesions, 12 of which presented in adults. Five of 16 type 1 CCAMs were accompanied by microscopic foci of bronchioloalveolar carcinoma; two others showed focal mucous cell hyperplasia. In two further cases, foci of nonmucinous atypical adenomatous hyperplasia were identified in the adjacent lung parenchyma. The bronchioloalveolar carcinomas showed less cytologic atypia, proliferative activity (Ki-67), and p53 expression than a comparative group of bronchioloalveolar carcinomas arising de novo, but this was not statistically significant (p = 0.15). Neither bronchioloalveolar carcinomas nor hyperplasia was identified in type 2 or type 4 CCAMs. Four of the eight type 4 CCAMs showed focal stromal hypercellularity, and one case subsequently developed a pleuropulmonary blastoma. We conclude that classification according to the current system is of clinical value. Bronchioloalveolar carcinomas arise in association with type 1 CCAMs, but recurrence following resection is exceptional. Type 4 CCAMs show histologic overlap with grade 1 pleuropulmonary blastomas, and distinction between these entities may not be possible on histology alone. However, stromal cellularity in a type 4 CCAM should raise the possibility of blastomatous transformation.