Which form of asbestos is most commonly associated with maximum risk of Mesothelioma?
Ans. D. Crocidolite. (Ref. Robbin's basic Pathology 8,h/pg. Chapter 13 & Internet)Malignant epithelioma, commonly occurs following chronic exposure (>20 years) to asbestos. Consider this diagnosis in those employed in milling and construction, as well as in workers in pipe, textiles, gaskets, and other industries in which asbestos (especially crocidoliteform) is used. In 75%, the diffuse (malignant) form occurs.Asbestosis and Asbestos-Related Diseases# Asbestos is a family of crystalline hydrated silicates with a fibrous geometry.# On the basis of epidemiologic studies, occupational exposure to asbestos is linked to# (1) parenchymal interstitial fibrosis (asbestosis); (2) localized fibrous plaques and calcifications or, rarely, diffuse fibrosis in the pleura; (3) Round atelectasis (4) pleural effusions; (5) bronchogenic carcinoma; (6) malignant pleural and peritoneal mesotheliomas; and (7) laryngeal carcinoma.# Pathogenesis: Concentration, size, shape, and solubility of the different forms of asbestos dictate whether disease will occur. There are two distinct forms of asbestos:o Serpentine (in which the fiber is curly and flexible) and amphibole (in which the fiber is straight, stiff, and brittle). There are several subtypes of curly and straight asbestos fibers. The serpentine chrysotile accounts for most of the asbestos used in industry.o Amphiboles. even though less prevalent, are more pathogenic than the serpentine chrysotile, but both types can produce asbestosis, lung cancer, and mesothelioma. The straight, stiff amphiboles, in contrast, align themselves in the airstream and are hence delivered deeper into the lungs, where they may penetrate epithelial cells and reach the interstitium.# Morphology: Asbestosis is marked by diffuse interstitial fibrosis with distinct "Ferruginous bodies" /asbestos bodies, (golden brown, fusiform or beaded rods with a translucent center, consisting of asbestos fibers coated with an iron-containing proteinaceous material.Educational points:Silicosis# is currently the most prevalent chronic occupational disease in the world.# It is caused by inhalation of crystalline silica, mostly in occupational settings.# Silica occurs in both crystalline and amorphous forms, but crystalline forms (including quartz, cristobalite, and tridymite) are by far the most toxic and fibrogenic.# Of these, quartz is most commonly implicated in silicosis.0# Ingested silica particles cause activation and release of mediators by pulmonary macrophages, including EL-1, TNF, fibronectin, lipid mediators, oxygen-derived free radicals, and fibrogenic cytokines. It has been noted that when mixed with other minerals, quartz has a reduced fibrogenic effect.# Silicotic nodules are characterized grossly in their early stages by tiny, barely palpable, discrete, pale-to-blackened (if coal dust is also present) nodules in the upper zones of the lungs. Microscopically, the silicotic nodule demonstrates concentrically arranged hyalinized collagen fibers surrounding an amorphous center. The "whorled" appearance of the collagen fibers is quite distinctive for silicosis.# Examination of the nodules by polarized microscopy reveals weakly birefringent silica particles, primarily in the center of the nodules. As the disease progresses, the individual nodules may coalesce into hard, collagenous scars, with eventual progression to PMF.# The intervening lung parenchyma may be compressed or overexpanded, and a honeycomb pattern may develop. Fibrotic lesions may also occur in the hilar lymph nodes ("eggshell" calcification) and pleura.Educational table:Mineral Dust-Induced Lung DiseaseAgentDiseaseExposureCoal dustSimple coal workers' pneumoconiosis: macules and nodules Complicated coal workers' pneumoconiosis: PMFCoal miningSilicaSilicosisSandblasting, quarrying, mining, stone cutting, foundry work, ceramicsAsbestosAsbestosis pleural effusions, pleural plaques, or diffuse fibrosis; mesothelioma; carcinoma of the lung and larynxMining, milling, and fabrication of ores and materials; installation and removal of insulationSelected Causes of Hypersensitivity PneumonitisSYNDROMEEXPOSUREANTIGENFarmer's lungMoldy hayMicropolyspora faeniBagassosisMoldy pressed sugar cane (bagasse)Thermophilic actinomycetesMoldy maple barkCryptostroma corticate Humidifier lungCool-mist humidifierThermophilic actinomycetes, Aureobasidium pullulansMalt worker's lungMoldy barleyAspergillus cl a vat usCheese washer's lungMoldy cheesePenicillium caseiMiller's lungDust-contaminated grainSitophilus granarius (wheat weevil)Pigeon breeder's lungPigeonsPigeon serum proteins in droppingsChemical worker's lungChemical industryTrimellitic anhydride, isocyanates
Chrysolite
Amosite
Anthophyllite
Crocidolite
Respiration