Table 13.3 ). Although statistics vary, it seems that less than 10% of cases of simple CWP progress to PMF. Of note, PMF is a generic term that applies to a confluent fibrosing reaction in the lung; this can be a complication of any of the pneumoconioses discussed here.
Although coal is mainly carbon, coal mine dust contains a variety of trace metals, inorganic minerals, and crystalline silica. The ratio of carbon to contaminating chemicals and minerals (“coal rank”) increases from bituminous to anthracite coal; in general, anthracite mining has been associated with a higher risk for CWP.
MORPHOLOGYPulmonary anthracosis isthemostinnocuouscoal-inducedpulmonarylesionincoalminersandalsoiscommonlyseeninurbandwellersandtobaccosmokers.Inhaledcarbonpigmentisengulfedbyalveolarorinterstitialmacrophages,whichthenaccumulateintheconnectivetissuealongthepulmonaryandpleurallymphaticsandindraininglymphnodes.
Simple CWP ischaracterizedbythepresenceofcoal macules andlargercoal nodules. Thecoalmaculeconsistsofdust-ladenmacrophagesandsmallamountsofcollagenfibersarrayedinadelicatenetwork.Althoughtheselesionsarescatteredthroughoutthelung,theupperlobesandupperzonesofthelowerlobesaremoreheavilyinvolved.Induecourse,centrilobular emphysema mayoccur.FunctionallysignificantemphysemaismorecommonintheUnitedKingdomandEurope,probablybecauseintheselocalesthecoalrankishigherthanintheUnitedStates.
Complicated CWP (PMF) occursonabackgroundofsimpleCWPbycoalescenceofcoalnodulesandgenerallydevelopsovermanyyears.Itischaracterizedbymultiple,darkblackscarslargerthan2cmandsometimesupto10cmingreatestdiameterthatconsistofdensecollagenandpigment(
Fig.13.16
CWP usually is a benign disease that produces little decrement in lung function. In those in whom PMF develops, there is increasing pulmonary dysfunction, pulmonary hypertension, and cor pulmonale. Progression from CWP to PMF has been linked to a variety of variables including higher coal dust exposure levels and total dust burden. Unfortunately, once established PMF has a tendency to progress even in the absence of further exposure. After taking smoking-related risk into account, there is no increased frequency of lung carcinoma in coal miners, a feature that distinguishes CWP from both silica and asbestos exposures (discussed next).
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Fig. 13.16 Progressivemassivefibrosisinacoalworker.Alargeamountofblackpigmentisassociatedwithfibrosis.(From Klatt EC: RobbinsandCotranatlasofpathology,ed 2, Elsevier, Philadelphia, p 121.)