Document N6V4oeoqyK42wmkvVMEBX35w

'i Vol. 50 In'p'3'*'*'*" ^wlingi o1-. Hannover. new* reside in frequency h*r 55). Proc an breast Mb/ >c!oss H. Inti-asts." Cancer rom statistical an breast can- ia J. The bi'oma. Cancer Jen G. Cancer in Alameda rrea P. Powel n: IARC Sd- -r risk predic- Pulmonary Asbestos Body Counts and Electron Probe Analysis of Asbestos Body Cores in Patients with Mesothelioma A Study of 25 Cases VICTOR L. ROGGU, MO.* MALCOLM H. McQAVRAN, MD.t JAMES SUBACH. PhD,$ HARLEY O. SYBERS. MD. PhO, AND S. DONALD GREENBERG. MD| Malignant mesotheliomas of the pleura and peritoneum are well-recognized risks of asbestos exposure. We determined the asbestos body content of the lungs from 24 cases of malignant mesothelioma (19 pleural, five peritoneal) and compared such to the content of lungs from 50 consecutive adult autopsies and four cases of overt asbestosis using a Clorox-digestion concentration technique. The cores of 90 asbestos bodies were examined by energy dispersive x-ray analysis and compared with similar data from 120 standard asbestos fibers and 20 fiberglass fibers. The malignant mesothelioma patients had asbestos body counts intermediate between those of the general population and those of patients with asbestosis, although some of the mesothelioma cases overlapped with the general population. These latter cases often lacked an identifiable occupational exposure to asbestos. EDXA studies demonstrated an amphibole core in 88 of the 90 asbestos bodies (amosite or crocidolite in 80 of 88, anthophyllite or tremolite in eight of 88), and chrysotile in two instances. Cancer 50:2423-2432,1982. he association between occupational asbestos ex occasional case of mesothelioma with low level occu T posure and the subsequent development of malig pational exposure to asbestos has been described.7 nant mesothelioma of the pleura or peritoneum was first The increase in the number of reported cases of a established by Wagner et al. in I960.1 Since this initial malignancy previously thought to be rare led to inten study, several series of mesotheliomas have been re sified interest in asbestos and asbestos-related diseases. ported confirming the association with asbestos expo Quantitative methods for the concentration and isola sure.2-4 Cases have been reported in the wives and chil tion of ferruginous (asbestos) bodies, the hallmark of dren of asbestos workers, who were apparently exposed asbestos exposure, demonstrated that these structures to the dust brought home on the workers' clothes.4-4 An may be found in 90-100% of the general popula- tion,*-10 and that the numbers of ferruginous bodies From the Department of Pathology, Baylor College of Medicine and The Methodist Hospital. * Chief Resident and American Cancer Society Fellow, 1979-1980. found in the lungs of such individuate at postmortem examination appear to have increased over the past three decades.11 The specificity of the ferruginous body as a t Professor and Chief of Anatomic Pathology. t Research Instructor, Baylor College of Medicine, Visiting Scien tist, NASA, Johnson Space Center. $ Associate Professor of Pathology. marker for asbestos exposure was challenged by the demonstration in animal models that a number of fi brous dusts other than asbestos may result in the for I Professor of Pathology. Address for reprints : Victor L. Roggli, MD, Department of Pa thology, Duke University Medical Center, Durham, NC 27710. We thank Dr. V. Timbrel), MRC Pneumoconiosis Unit, Uandough mation offerruginous bodies.12 Problems ofobvious im portance which follow from these observations are the magnitude of asbestos exposure and tissue asbestos load Hospital, Penarth, Glamorgan, United Kingdom, for providing sam ples of the U.I.C.C. asbestos standards; Dr. B. N. Powell, Rice Uni versity Dept, ofGeology, Houston. Tx., for providing samples oftrem olite asbestos; and Dr. J. L. Konzen and Mr. R. S. Atkinson ofOwens- in patients with mesothelioma, and the nature of the cores of ferruginous bodies found in these individuate; i.e., might fibrous dusts other than asbestos be impli ' Coming Fiberglass Corp. for providing samples of "fine fiber" fibrous cated in the pathogenesis of mesotheliomas in humans. glass. Also, we are indebted to Eleanor Collier, CT (ASCP), and Sadie Speaker for technical assistance. Few studies have been reported in which quantitation Accepted for publication January 4, 1982. of ferruginous bodies or uncoated fibers within lung tis- 10003049 0008-543X/8?/1201/1423 $U0 American Cairo Society OTTCB&TJ THIS MATERIAL MAY BE PROTECTED B*^COPYRIGHT LAHl (- r . \T'T\ 17 U.S. CODE) t { 2424 Cancer December l 1982 Vol. 50 No. II sue from mesothelioma patients was attempted.3,13,14,13,14 (range, 21-89 years), and there were 29 men and 21 In a few instances, electron probe analysis or electron women. None of those individuals had overt pulmonary diffraction techniques were used to investigate the chem interstitial fibrosis, pleural plaques, or mesothelioma. ___Ci ical and structural nature of the ferruginous body Also, for the purpose of comparison with the mesothe Pleural cores.3,13,17 This report is an analysis of the cases of lioma group, four individuals with asbestosis were in malignant pleural and peritoneal mesotheliomas seen cluded in the study. These four men had an age range 1/6 in at our institution over the past 17 years. An attempt was of 54-76 years, and three had carcinoma of the lung. lit made to correlate the ferruginous (asbestos) body counts in lung tissue with occupational information, and with Occupational Data similar data obtained from patients with asbestosis and a from a control autopsy population. In selected cases, Information concerning the occupation of individuals energy dispersive (electron probe) X-ray analysis (EDXA) in the study and control groups was obtained by review and selected area electron diffraction (SAED) were per of the hospital chart, and by direct phone conversation formed on isolated ferruginous bodies to determine the with a living relative or, in a few cases, with the private nature of the fibrous core. physician. Direct inquiries were made into all occupa tions (both recent and remote), place of residence, war Materials and Methods Patient and Control Populations time experience, e.g., shipyards, spouse's employment, and hobbies. Duration of employment was also re corded. Information was available on all 25 mesotheli The study group consisted of all cases of malignant mesotheliomas (pleural and peritoneal) diagnosed at The Methodist Hospital from January 1963 to March 1980. Criteria for the diagnosis of malignant (diffuse) pleural mesothelioma have been previously de scribed,1*-20 and include the following: (1) predilection to spread along the pleural surface and major fissures, with total encasement of the lung in advanced cases; (2) compatible microscopic appearance of the tumor, oma cases, all four asbestosis cases and 49 of 50 controls. From autopsy results of 57 initial controls, seven were eliminated because of occupational data obtained by phone interview with relatives: two pipefitters, two weld ers, one boilermaker, one engineer who had worked in shipyards intermittently, and one cabinet maker with relatively high asbestos body counts whose relatives could not be contacted for further occupational infor mation. 4/6 M 6/1 7/! 8/6 9/6 10/1 11/t 12/IV* H/: l5/< 16/. 17/18/. 19/ Perito 20/ 21/ 22/ 23/ 24/ 25/ 9 Other which includes four basic patterns: a: tubular or tubulopapillary epithelial type; b: predominantly solid, pleo morphic epithelial type; c. sarcomatoid or spindle cell variant; and dr. a mixture of one or more of the previous patterns. The identification of acid mucopolysaccharide which is sensitive to hyaluronidase as demonstrated by the Alcian blue stain, and the absence of neutral mucin using the periodic acid-Schiff (PAS) with diastase, are helpful histochemical features. Malignant (diffuse) peri toneal mesotheliomas show a predilection to spread along the parietal peritoneum and serosal surface of ab dominal viscera, with a similar range of microscopic and histochemical features as seen in pleural mesothe liomas.21-22 A single case of benign fibrous pleural me sothelioma included in the study showed features iden tical to those described by others.23 Postmortem ex amination did not demonstrate a visceral primary malignancy in any of the cases included in this study. Twenty-five cases of mesothelioma were identified in our files using these criteria: 18 cases of malignant pleural mesothelioma, six cases of malignant peritoneal mesothelioma, and one localized fibrous tumor of the pleura. The control population consisted of 50 consecutive adult autopsies with no known occupational exposure to asbestos. The mean age for this group was 59.3 years Quantitation ofAsbestos Bodies Weighed samples of formalin-fixed lung (4.5--5.5 g), obtained at autopsy from 23 of 25 mesothelioma pa tients and at time of lobectomy for two of the meso thelioma patients, was processed by digestion with 5.25% sodium hypochlorite solution and subsequent iso lation, concentration, and enumeration of asbestos bodies per gram of lung tissue (wet weight) as previously described.10 Samples were taken chiefly from the lung periphery, avoiding areas of tumor, congestion, and con solidation as much as possible. In four instances (Cases 13, 18, 20, and 21), formalin-fixed lung tissue was no longer available, and paraffin blocks of lung were deparaffinized and rehydrated for digestion-quantitation studies. One to five blocks of lung tissue were available in each of these four cases. Lung tissue from the control cases and asbestosis cases was processed in the same manner as that for the mesothelioma cases. Quantitation of asbestos bodies was performed without prior knowl edge of occupational data. Electron Microscopic Studies 10003050 Selected cases from the mesothelioma and asbestosis groups were studied by transmission (TEM) and scan- > * r 26/ 27, 28, 29, t diseas tA Ch< ning disp tror pro* the chic ime sedi met cfc alee desi JEC x-ra tior pul: con exa. NOTICE: THIS MATERIAL MAY BE PROTECTED BY COPYRIGHT LAV. 07TLE 17 U.S COOP) 01. SO 1 No. II ASBESTOS AND MESOTHELIOMAS Roggli et al. 2425 J 21 nary 'ma. uhei ininge ng. uals iew tion -ate ipavar-*nt, reeliols. ere by ldin ith ves or- Case no./age/sex Pleural Mesothelioma 1/62/M 2/80/M 3/65/M 4/66/M 5/86/M 6/59/M 7/53/M 8/62/M 9/6 I/M 10/84/F 11/69/M 12/70/M 13/46/M 14/34/M 15/62/M 16/47/M 17/44/M 18/80/F 19/39/M Peritoneal Mesothelioma 20/6 I/M 21/60/M 22/54/M 23/S6/F 24/59/M 25/6l/F Table I. Ginical. Occupational and Pathologic Data on 25 Cates of Mesothelioma Occupation Diagnosis Latency* Pipe Insulator Asbestos plant inspector Pipefitter Shipyard worker Shipyard worker Commercial fisherman Welder, oil refinery Supervisor, chera company Superintendent, engr corp FBI agent OfTc worker, oil refinery Chem engr Tugboat capt Proj engr Supervisor, paper fact Engr, chem co Accountant ~ Housewife Butcher Malig, sar type. Lt; asbestosis Malig, tubulopap & solid epithelial. Lt; asbestosis Malig, tubulopap, Rt Malig, tubulopap. Lt Malig, mixed sar & pap, Rt Malig. pleo solid epithelial type, Lt Malig, sar type. RT Malig, mixed sar & solid epithelial, Lt Malig. mixed pap-sar-pteo undifT, Lt Malig, pleo epithelial type. Lt Malig, tubulopap & pleo epithelial type. Lt Malig, sar type. Lt Malig. tubulopap. Lt Malig, pleo epithelial type. Rt Malig, sar type. Lt Malig, tubuloacinar. Lt Malig, mixed sar & pap, Lt Malig, mixed sar & pap, Rt Benign, solitary, fibrous, Rt 40 yr 29 yr 37 yr 35 yr 30 yr -- 18 yr 16 yr 38 yr -- 20-30 yr -- --- ' -- -- -- -- -- Insulator Estimator Janitor Housewife Mgr. produce co Housewife Mixed, sar & pap Tubular type Sartype Tubulopap Tubulopap Pap type 22+yr -- -- -- -- -- AB/gf 29.700 26.400 480 380 280 160 130 91 80 19 8.1 7.6 6.7 2.0 1.5 1.4 <1 <1 3.8 380 215 3.5 1.2 <1 <1 Other 26/76/M Guard, asbestos plant Asbestosis. sq ca lung 20 yr 30.900 27/73/M Insulation sprayer Asbestosis Many yr 10.100 28/69/M Insulator Asbestosis. sq ca lung 40+ yr 1500 g). 29/54/M Pipe insulator Asbestosis. adenoca lung 34 yr 1200 >a- .o- * Time from initial occupational asbestos exposure till diagnosis of disease. ery; capt: captain; proj: project; fact factory, mgr manager, Rt: right; Lt; left; sq ca: squamous cell carcinoma; adenoca: adenocarcinoma; :th t Asbestos bodies per gram lung tissue (wet weight). Pap: papillary; Tubulopap: tubulopapillary; Malig: malignant; Sar sar -0- Chem co: chemical company; engr engineer; oflc: office; ref: refin comatous; Pleo: pleomorphic, AB: asbestos bodies. OS iy ning transmission (STEM) electron microscopy, energy Asbestos bodies were not found by this technique in dispersive x-ray analysis (EDXA), and selected area elec cases with less than 19 asbestos bodies (AB)/g lung tissue n- tron diffraction (SAED). Samples of lung tissue were (Table 1), and there was insufficient tissue for electron es processed by digestion in 5.25% sodium hypochlorite, microscopic studies in those cases with counts higher to the residue extracted in an equal volume mixture of than 19 AB/g seen at our institution prior to 1975, (f.g.. e- chloroform and 50% ethyl alcohol, the centrifuged sed Cases 5, 6, 20, and 21). m iment suspended in 95% ethyl alcohol, and 5 til of the Fiber length and diameter measurements were ob le sediment transferred onto a nitrocellulose coated 300- tained for 50 standard fibers, and compared with the ol mesh nylon grid. UICC asbestos standards and a sample length and core diameter of 50 asbestos bodies (37 from le ofcommercial fibrous glass were suspended in 95% ethyl patients with pleural mesothelioma and 13 from patients >n alcohol, and 5 #d samples transferred to nylon grids as with asbestosis). EDXA was performed on 90 asbestos I- described above. All specimens were examined in a body cores (59 from patients with pleural mesothelioma JEOL-100C electron microscope equipped with a Kevex and 31 from patients with asbestosis) employing a tilt x-ray energy dispersive spectrometer (Kevex Corpora angle of 37, accelerating voltage of 60 KV, and collec tion, Burlingame, California) and a Tracor-Northern tion time of 100 seconds. This was compared with pulse analyzer (Tracor Northern, Inc., Middleton, Wis EDXA data from 20 fibers of each of the five UICC is consin) and computer interface. One to three grids were asbestos types (amosite, crocidolite, anthophyllite, and examined per case, and the entire grid scanned at 2000x. chrysotile A and B) as well as 20 fibers of tremolite 1000305' ft-'' NOTICE: THIS MATERIAL MAY BE PROTECTED BY COPYRIGHT LAV. .rrj (TJTIE 17 U.S. CODE' 2426 Cancer December 1 1982 Vol. 50 ^o. II Table 2. Distribution of Metastases in 24 Cases of Malignant Mesothelioma (Pleural and Peritoneal) Metastatic site No. of cases* Lymph nodes Lungs Liver Adrenal glands Pericardium A epicardium Kidneys Bone Peritoneum Pancreas Pleura,! omentum, mesentery, brain, stomach, gastrointestinal tract, gallbladder, trachea, thyroid, chest wall & skeletal muscle 16(4) 10 8(1) 7 3 4 3 2 2 1 ea * Represents total number of cases with metatases to given sites, with number of peritoneal mesothelioma cases indicated in parenthe ses. t Peritoneal mesothelioma with pleura metastases. (provided by the Geology Department of Rice Univer sity, Houston, Texas) and 20 fibers of commercial fi brous glass (provided by Owens-Coming Co.). SAED patterns were obtained from 12 asbestos body cores and 14 standard asbestos fibers. Analysis ofEDXA Data The relative peak heights for seven elements--mag nesium (Mg), silicon (Si), calcium (Ca), sodium (Na), manganese (Mn), iron (Fe), and aluminum (Al)--were measured for each standard fiber and each asbestos body core analyzed. Values for the relative peak-height per centage of these seven elements were plotted on a Gibbs triangular coordinate diagram.24 In addition, the asbes tos body cores were further classified using a discrimi nate function analysis technique based on the data from the 140 standard fibers. The method is similar to that described by Millette and McFarren25 for the classifi cation of amphiboles, but has been extended to include chrysotile and fiberglass as well. Results The age, sex, occupational data, diagnosis, time from initial exposure to asbestos to presentation with asbestos- Table 3. Distribution of Histologic Types of Malignant Mesothelioma in 24 Patients With and Without Occupational Asbestos Exposure* Histologic type With asbestos exposure Without asbestos exposure Tubulopapillary Pleomorphic (solid) epithelial Sarcomatous Mixed 3(1) I 2 5(1) 3(3) 2 3(1) 3 * No. represents total number of cases with given histologic type, with number of peritoneal mesothelioma cases indicated in pa rentheses. related disease (latency), and AB/g lung tissue (wet weight) for the mesothelioma and asbestosis cases are shown in Table 1. The mean age for the 23 mesothe lioma patients is 60.8 years, and the group includes 21 men and four women. Occupational Data Eleven of the 24 individuals with malignant meso thelioma had a history of occupational exposure to as bestos. Three were pipefitters or insulators (Cases 1, 3, and 20), three had been employed in shipyards (Cases 4-6), three had a history of asbestos exposure while working in oil or chemical refineries (Cases 7-9), and one was employed in a plant which manufactured as bestos products (Case 2). One individual (Case 12) was a chemical engineer who was exposed to asbestos while developing insulation for boilers. The duration of em ployment in an asbestos-related occupation for these 11 patients ranged from 2-40 years. The mean latent period from initial exposure until the detection of mesotheli oma was 29 years for ten of these workers (unknown for Case 6). The occupation for the four patients with as bestosis but without mesothelioma (Cases 26-29) in cluded insulation employing asbestos materials (three cases) and guard for an asbestos plant (one case); the duration of employment ranged from 7-18 years, and the mean latent period was over 30 years. None of the other 14 patients with mesothelioma (including the one individual (Case 19) with a localized fibrous tumor of the pleura) had an identifiable exposure to asbestos. Pathologic Findings Autopsies were performed in 23 cases of mesotheli oma, and in two cases material from surgical resection (Cases 8 and 19) was available for study. Metastases were present in 21 of 23 cases at autopsy, with a distribution as shown in Table 2. In addition, metastases to regional nodes were present in the lobectomy specimen of Case 8; this patient died approximately one year after surgery; an autopsy was not performed. The distribution of his tologic types of mesothelioma for individuals with and without asbestos exposure is shown in Table 3; there is no significant difference in distribution of tumor types between these two groups (P = 0.72). The patient with a localized fibrous tumor of the pleura (Case 19) had a IS cm ovoid well circumscribed mass attached poste riorly to the right lower lobe. There was no evidence of metastatic disease, and he is alive and well seven months postlobectomy. Quantitation ofAsbestos Bodies The distribution of asbestos body counts for the pa tients with asbestosis and mesothelioma as compared to Fig. i ruginous malin-fi) tosis ca* the co tients tos bo one oi with 1 infom tients <1-1* hadic body AB/g; Fig or iyp areas ofiroi and a ysis {' j 10003052 HOTICEr THIS MATERIAL MAY BE PROTECTED BY COPYRIGHT LAW. <T:VJ 17 V.S core) v0). so , (wet s are othees 21 No. 11 Asbestos and Mesotheliomas Roggli et al. 2427 lesoo as1.3, 'ases hile and : aswas hile .m- II "iod :elilor asinree ihe md he ne of li>n re m al se y; sd is s h a f s FiG. 1. Bar diagram showing distribution of fer ruginous (asbestos) body counts per gram of wet for malin-fixed lung tissue for mesothelioma and asbev tosis cases as compared to controls. FERRUGINOUS BODIES PER GRAM LUNG TISSUE (Wei Weight) the control population is shown in Figure 1. Eleven pa tients with mesothelioma had lung parenchymal asbes tos body counts ranging from 80-29,700 AB/g; all but one ofthese individuals was employed in an occupation with known exposure to asbestos (complete historical information not available for Case 21). Fourteen pa tients with mesothelioma had asbestos body counts of <1-19 AB/g; only one of these individuals (Case 12) had identifiable exposure to asbestos. The mean asbestos body counts for the three groups were: asbestosis, 10,900 AB/g; mesothelioma, 2330 AB/g; and control popula tion, 1.2 AB/g. Asbestos bodies were found in the lungs of 92% of individuals in the control population. Electron Microscopic Studies Electron microscopic studies of asbestos bodies show electron dense central libers, or "cores", with discontin uous coated areas, consisting of iron-protein-mucopolysaccharide material deposited by macrophages.26 Un coated areas, as shown in Figure 2, are suitable for EDXA and SAED studies. The results of EDXA analysis Fig. 2. Transmission electron micrograph of typical asbestos body from Patient 2. Bare areas (arrows) between the irregular masses ofiron-protein coating represent the core fiber and are suitable for EDXA and SAED anal ysis (X9800). !' > NOTICE: THIS MATERIAL MAY BE 2428 Cancer December 1 1982 Vol. so Al.Ca, Na Discussion Fig. 3. Gibbs triangular coordinate diagram showing relative ele mental composition for several types offibrous minerals (broken lines), based on analysis of 20 standard ftben of each type: Amos: amosite; Croc crocidolite: Anthoph: anthophyllitr, Tiem: tremolite; Chrys: chrysotile A and <6; FBG: fiberglass. Dots represent analyses of 90 individual asbestos body cores from patients with mesothelioma (59 cores) and asbestosis (31 cores). for elemental composition of90 asbestos body cores and 140 standard fibers are plotted on the Gibbs triangular coordinate diagram in Figure 3. The majority of the asbestos body cores (80/90) fall within the area occupied by amosite and crocidolite standard fibers. Two asbestos body cores are located in the area occupied by the trem olite standards, and one within the chrysotile area. The relative percentage of four major elements (Mg, Si, Ca, and Fe) based on peak height measurements for the 90 asbestos body cores as well as the standard fibers are shown in Table 4. Classification by discriminate func tion analysis showed that 80 of 90 cores were most prob ably amosite or crocidolite, four each were tremolite or anthophyllite, and two were chrysotile. SAED studies showed that the asbestos body core had a crystallinelattice structure compatible with that of amphibole as bestos for all 12 cores for which a diffraction pattern was obtained (figs. 4A and 4B). The core diameter for 37 asbestos bodies from pa tients with mesothelioma as measured from scanningtransmission electron micrographs was 0.41 0.21 ft, and for 13 bodies from patients with asbestosis was 0.27 0.13 m (mean 1 SD). The diameter for 39 UICC standard fibers was 0.60 0.32 ft, for three tremolite libers 1.24 0.46 ft, and for eight fiberglass fibers 1.38 1.15 The mean length for the asbestos bodies was 34.13 19.90 ft as compared to 18.03 11.44 ft for the 30 standard fibers. The clinical and pathologic features of the cases of mesothelioma in the current study are similar to those reported in other series:5-4-27 the majority of the patients are men (83% in our series) in the sixth or seventh decade of life; pleural mesotheliomas are seen more frequently than peritoneal (75 versus 23%); and epithelial types are more common than sarcomatous or mixed types (54, 21, and 25%, respectively). Histochemical studies (AJcian blue hyaluronidase and PAS diastase) gave variable results: stromal Alcian blue positive material was sensitive to hyaluronidase, whereas intraepithelial Alcian blue positive material was either partially sensi tive or resistant to hyaluronidase. However, none of our cases contained PAS-positive material which was dias tase resistant. Thus, we believe that while histochemical findings may supplement the gross and microscopic fea tures in the diagnosis of mesothelioma, they are not, in themselves, reliable independent diagnostic criteria. As bestos body counts in the pulmonary parenchyma of mesothelioma patients with a history of asbestos expo sure but without asbestosis, (Cases 3-9, 20, 21) gave a mean- count of 244 AB/g lung (wet formalin-fixed weight). The mean count for all malignant mesotheli oma cases without asbestosis (Cases 3-18, 20-25) was 90 AB/g lung. The relatively low count (3.8 AB/g) in the single case of localized fibrous tumor of the pleura is consistent with the failure to correlate the occurrence of this neoplasm with exposure to asbestos.53-5* The percentage of patients with malignant mesothe lioma of the pleura or peritoneum from whom a history of substantial asbestos exposure has been obtained has varied widely from one study to another.3,4-27 A history of asbestos exposure was obtained in 46% of our cases of malignant mesothelioma by direct telephone inter view with living relatives. This figure correlates well with that obtained in a previous large epidemiologic study of malignant mesothelioma in North America,29 in which just under one half of the men (but only 5% of women) with malignant mesothelioma had an identifiable oc cupational exposure to asbestos. Although Cochrane and Webster3 have emphasized the hazards inherent in obtaining histories from family members or fellow work ers, it seems likely that our cases with a negative history of asbestos exposure were correctly classified as such, since all but one (Case 21) of the 13 malignant meso thelioma patients from whom a history of asbestos ex posure was not obtained had asbestos body counts in the lung which overlapped with the counts obtained from the control population (Fig. I). Similarly, all but one (Case 12) of the 11 malignant mesothelioma cases 10003034 Ttl' ' -- NOTICE: THIS MATERIAL MAY BE PROTECTED BY COPYRIGHT LAV. (T'HE V H. VoL 30 ses Of those meats lecade Jently cs are s (54, s(Algave terial helial iensi>four diasnical : fea3t, in . As ia of xpoive a fixed heli-, was ;) in aura. :nce thetory has ory lses terith / of ich -n) octne in rkiry -h, >0- xin ed ut No. n ASBESTOS AND MESOTHELIOMAS Roggli et dl. 2429 Table 4. Relative Percentage Elemental Composition of Cores or 90 Asbestos Bodies from Patients with Pleural Mesothelioma* Cores Elements N* Amosite-crocidolite (40) Mg Si Cm Fe Anthophyllite (20) N Mg Si ca Fe Tremolite (20) N MS Si Ca Fe Chrysotile (40) N Mg Si Ca Fe Ref. SuLt- 4.26 0.77 45.98 3.17 4.01 1.98 45.75 5.83 20.51 2.17 62.72 3.25 4.49 2.32 12.28 2.43 16.29 2.84 57.97 5.59 21.94 7.50 3.80 2.21 32.52 4.97 36.18 5.53 4.80 2.78 6.51 2.98 Case 1 (10) Case 2 (20) 4.17 28.89 3.96 62.97 4.70 32.05 5.70 57.54 Case 4 (10) 5.40 36.17 8.10 50.32 Case 8 (2) 1.31 29.33 8.91 60.46 Case 9 (10) (6) 5.66 43.92 5.94 44.48 Case 10 (7) (1) 4.02 34.65 9.09 52.25 (1) 2.38 70.11 12.43 15.08 (3) 7.95 57.11 16.27 18.67 (1) 15.90 58.07 22.97 3.06 (3) 19.27 65.62 8.53 6.58 <2 29.94 2.26 30.96 91.43 8.92 2.75 10.19 3.34 Case 26 (10) 3.73 36.20 9.18 50.88 Case 27 (ID 5.10 32.78 6.10 56.02 Case 29 (10) 4.02 40.62 4.81 50.55 * Includes data from six patients with mesothelioma (Cases I, 2. 4, 8,9,10), 2 with asbestosis and lung cancer (Cases 26, 29) and one with asbestosis (Case 27). t Reference standards show mean I SD for number of fibers indicated in parenthesis. | N (numbers in parenthesis under case no.) indicate number of fibers analyzed per case. Data for these two fibers shown separately because one fiber showed considerable in Wro leaching of Mg. from whom a positive history of asbestos exposure was obtained had asbestos body counts far greater than those seen in the control population. Of the patients with mesothelioma, the two individuals (Cases 1 and 2) who also had pulmonary interstitial fibrosis (asbestosis) had the highest pulmonary asbestos body counts. There was no difference in the morphologic features of mesothe liomas from patients with occupational asbestos expo sure as compared to those without occupational expo sure (Table 3). Several possible alternatives should be considered in attempting to explain the occurrence of mesotheliomas in patients with no occupational exposure to asbestos and low asbestos body counts (<20 AB/gm) in the; lung. One hypothesis is that there is no threshold level of as bestos exposure below which mesotheliomas will not occur, hence a certain small percentage of susceptible individuals will develop mesothelioma in any industrial ized society in which there is ubiquitous (albeit low level) asbestos contamination of the environment.10 Evidence in support ofan inherited susceptibility for development of malignant mesothelioma has recently been presented in a report of familial clustering of five cases of malig nant mesothelioma (three peritoneal and two pleural mesotheliomas).3' A second possibility is that those individuals with low asbestos body counts were subjected to undetected oc cupational or environmental exposure to submicroscopic asbestos fibrils or to chrysotile asbestos, which does not readily form asbestos bodies.32 However, stud ies by Ashcroft and Heppleston33 have shown that the ratio of asbestos bodies to uncoated asbestos fibers (as determined by phase contrast microscopy) and to submicroscopic fibers (enumerated by electron microscopy) remains rather constant. Thus asbestos bodies are found in the presence of larger numbers of uncoated and submicroscopic fibers. In addition, various studies have cast doubt on the likelihood that short fiber (<5 /* in length) and submicroscopic asbestos particles per se are either fibrogenic or carcinogenic,34 although an isolated case of pulmonary interstitial fibrosis with large numbers of submicroscopic chrysotile fibers in the lungs has been ... . .. 1000303* ' NOTICE: THIS MATERIAL MAY BE PROTECTED BY COPYRIGHT LAV. (VJTIE 17 U.S, CODE) 2430 Cancer December l 1982 VoL JO Figs. 4A and 48. Selected area electron diffraction (SAED) patterns obtained from a U.I.C.C. amosite standard fiber (A, left) and an asbestos body core (B. right) from Patient 2 show identical layer line spacings as measured from photograph negatives. The pattern or each is typical oT amphibole asbestos. describe^35 The study by Morgan and Holmes16 dem onstrated that in patients with mesothelioma it is the long amphibole fibers which tend to accumulate in lung parenchyma, and it is these fibers which have the greatest likelihood of becoming coated, (i.e., asbestos bodies). Conversely, in individuals from the general population with low asbestos body counts and no evidence of as bestos-related disease, large numbers of short (<5 n) chrysotile fibers may be identified.36 These data are con sistent with the experimental findings of Stanton37 that long thin fibers are the most efficient in the induction of mesotheliomas. A third alternative is that factors other than asbestos may be involved in the pathogenesis of mesothelioma.2 Case 17 in our series was a patient who had been treated for tuberculosis by thoracic plumbage with instillation of leucite spheres 20 years prior to the diagnosis of me sothelioma of the ipsilateral pleural cavity; this patient had very low levels of asbestos bodies in the lung. In addition, an excessive number of our patients with me sothelioma (29%) were employed in the petrochemical or oil refinery industry, or in engineering jobs involving site visits at a refinery or chemical plant (the percentage of the population employed by these industries is 2% for Harris County and the Greater Houston area, and 618% for adjacent counties on the Gulf Coast31). How ever, Lilis et al.i9 have pointed out the risk of asbestos exposure among certain employees of chemical plants and oil refineries,40 and have described pleural thick ening and radiographic pulmonary opacities in a sub stantial percentage of these workers (33-40%), although cases of mesothelioma have not yet been identified. In our series, two of the oil refinery workers had occupa tions with probable asbestos exposure: one (Case 7) was a welder for 17 years, and the other (Case 11) was a former laborer and superintendent at a steel mill for six years. In addition, two of the chemical workers had his tories of occupational asbestos exposure: one (Case 8) as an insulation worker in the 1940s and 1950s, and one (Case 12) was exposed to asbestos while developing in- ' 10003054 NOTICE: THIS MATERIAL MAY BE PROTECTED BY' COPYRIGHT LAW. Of'TIE 17 U S v'i. sa, No. u ASBESTOS AND MESOTHELIOMAS Roggli el al. 2431 testos cal of iical 'ins lage for 6- ow- .tos nts ckabigh In oacas S3 SIX lis8) ne n- sulation for boilers. In one instance (Case 25), the pa tient's spouse was a chemical worker who did pipefitting and boiler work for 1 'A years. It is interesting to note that the seven workers em amosite and crocidolite regions on the Gibbs triangular coordinate diagram (Fig. 3), better separation of these two types was obtained by discriminate function anal ysis. However, three of the 40 known amosite and cra- ployed by an oil refinery or chemical company (Cases cidolite fibers were misclassified by this latter technique; , 7-9, 11, 12, 14, and 16) had relatively low pulmonary so we did not attempt to further separate the unkncwou asbestos body counts (<150 AB/g lung). This suggests fibers which were classified as amosite or crocidolite by a fourth alternative explanation for the development of computer analysis, since the increased iron content of mesothelioma in patients with low-dose asbestos expo coated fibers would likely magnify this error. The per sure, and that is a synergistic effect between asbestos and centage calcium peak height in the present study (Table some as yet unidentified environmental factor. The syn 4) was greater than that reported previously by other ergistic effect between asbestos and cigarette smoking in investigators45 because we did not correct for back the pathogenesis of bronchogenic carcinoma is well rec ground counts. ognized,41 although cigarette smoking has not been iden tified as a risk factor in the development of mesothe REFERENCES liomas.4 There is some experimental evidence that as bestos may act synergistically with radiation or chemical carcinogens in the induction ofmesothelioma.42 Further investigation is required to clarify the role of additional possible etiologic factors in the pathogenesis of meso thelioma. Electron microscopic and microanalytical studies on asbestos bodies from several of our cases confirmed the findings of previous investigators that practically all fer ruginous bodies isolated from the general popula tion41-*5 and the few previously isolated from patients with mesothelioma5''5,17 are nucleated on asbestos cores, the majority of which cores are amphiboles. We did not identify any type of fibrous dust other than asbestos in the small number of mesothelioma cases which we ex amined by EDXA and SAED. Interestingly, in Case 10, ( sjx of seven cores examined were anthophyllite or tremolite, which are known contaminants oftalc.44 However, we could not confirm a history of exposure to talc in this 84-year-old woman. Churg and Wamock previously noted that asbestos bodies with anthophyllite or trem- olite cores were isolated from women much more fre quently than from men,45 and suggested contamination of talc by these fiber types as a possible source. The asbestos body length and core diameter data reported by these investigators45 are in close agreement with sim ilar measurements of the 50 asbestos bodies described in the present study. Langer and associates47 have described leaching of Mg from chrysotile fibers in vivo, which was also noted in the two chrysotile cores identified in our study, and in I the four anthophyllite fibers as well (Table 4). In addi tion, the iron content of the asbestos body cores was in general greater than that of the corresponding standard fibers. The effects of these ionic shifts and their role in the pathogenesis of asbestos related diseases are cur rently poorly understood and require further investi gation.45 Although there was considerable overlap in the 1. Wagner JC, Sleggs CA. Marehand P. Diffuse pleural mesothe lioma and asbestosis exposure in North Western Cape Province. Br JlndMed I960; 17:260-271. 2. Borow M. Conston A. Livomese L, Schalet N. 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