Radiological features of diffuse mesothelioma

ENVIRONMENTAL

RESEAHCH

3, 330-338

Radiological

( 1970)

Features A.

Pne~rrnoconiosis

Research Johun~wdxrrg,

I7nit,

Sod

of

Mesothelioma

SOLOMON

So~lth Africm Africa unrl Receioccl

Diffuse

Council for Baraguxnath

April

Scientific Hospital,

und industrial Transvaal

Research,

13, 1970

Exposure to asbestos may cause small pleural cffusions, pulmonary fibrosis, pleural and peritoneal mesothelioma, or an increased tendency to carcinoma of the bronchus. In recent years there has been an increase in reports of mesothelioma (Stumphius and Meyer, 1968). By the end of 1961, a total of 87 pleural and 2 peritoneal mesotheliomas had been diagnosed in South Africa (Wagner, 1965). The South African Asbestos Tumour Registry has at present (1969) 179 cases diagnosed by the Asbestos Tumour Reference Panel as “definite” mcsothelioma. An association between asbestos and mcsothrlioma has been claimed, but in a number of cases there is no indication of exposure to asbestos according to Webster (1965). The inhalation of asbestos results in the formation of ferruginous bodies in the lungs, but these bodies have also been found in patients without known asbestos exposure. Nevertheless, evidence of exposure to asbestos is forthcoming in most cases of mesothelioma of the pleura. Previous radiological reports of this condition are usually scanty, and not correlative. The following is an analysis of a retrospective radiological study of 23 cases of pleural mesothelioma on which the pathology had been confirmed by the Asbestos Tumour Reference Panel of South Africa.

Sex of paGents

(23 cases)

age and sex distribution of the patients does not differ from other reported series. The high incidence of males may well reflect a selective factor as many of these particular patients were engaged in the mining of asbestos. The

HISTORY

OF

EXPOSURE

TO

ASBESTOS

Some of these patients had not actually handled the material but had lived in an area where mining and milling of asbestos took place. These regions are sub330

DIFFUSE

MESOTHELIOllA

TABLE EXPOSLIRE

331

II HISTORY

referred to as “calcific areas,” i.e., an endemic area where X-ray surveys havca revealed a large number of people with calcified pleural plaques. Contact with asbestos may bra trivial or massive. The kngth of exposure may be of long or short duration. The accepted latent period between csposurc and development of mrsothrlioma is SO40 years but this is probably cscrssivr. This scrics includc~s a patient aged 2 I vc’ars . Hadiographs wcrc’ available in the 23 casts and, thcreforc, this studv was made. The, casts prescntcd one or more of the following radiological featurtk:

scqwntly

PLEURAL

EFFI’SION

Fourteen cases presented with pleural effusions as the main X-ray feature. Of this group, six were right-sided and seven were left-sided pleural effusions. The effusions corresponded to the side of the pleural tumours as is to be expected. However, of this group, a patient with a mesothelioma of the right pleural serosa had bilateral e&ions on radiography. The reason for the left-sided pleural effusion remains unexplained.

332

A.

SOLOMON

The lobular edge of a pleural tumour in one instance, was seen above the level of the effusion. The silhouette of a large pleural tumour was obvious in a patient who presented with a hydropneumothorax. (Fig. 1.)

FIG. 1.. The silhouette of a large pleural tlunour is obvious in this case that presented a hydropnelunothoraa. Extensive nodular fibrosis is present in the opposite lung.

with

Perhaps the most interesting of the casts in patients with pleural effusions were the three with associated extrathoracic soft-tissue masses; two were noted in the left and the other on the right side. The masses were obvious on the X-rays and probably indicative of the primary occurred on the sidr of the cifusior~s and wtw pathology. In three patients with pleural &fusions, the contralatcral pleura showed extensive asillary lamellar thickening. Other accompanying pleural changes seen were extensive bilateral pleural sheets of calcification in one patient; in another patient a small calcified plaque was present on the side opposite to the effusion. Contralateral parenchymal lung changes were present in two other patients; in one the change was predominantly a nodular fibrosis and in the other a fine basal linear fibrosis. LOB~ILATION

OR

CRENATION OF THE PLEURAL DUE TO TUhlOUR ISVASION

SURFACE

In six cases a lobular pleural tumour was evident with no obvious radiographic change to suggest an associated pleural effusion. The tumour mass was extensive

DIFFUSE

333

MESOTHELlOhlA

in all but one case. In this instance the right minor fissure was the site of a small lobular tumour. The extent of the tumour mass in another patient was determined only in a lateral chest radiograph. Two patients with extensive pleural tumours had associated ipsilateral hilar masses, (Fig. 2.)

Additional featurrs in the opposite lung, suggestkre of asbestosis, were noted in thrcr C;~SCS.These consisted of fine basal fibrosis, a blunted costophrcnic s&us, and an asillary pleural lamellar reaction. Fiftecm patients in the series had lobular plcnral masses on X-ray. Aspiration of pkural fluid and an induced pneumothorax was nect’ssary to show the tumour in sis patic,nts. HILrZR

MASSE5

Hilar masse’s were present in six cases and were on the same side as the pleural tunK~rIr.

One casc~ showed

two rounded SOFT-TISSUE

lung lesions on the tmnour TUhIOITK

side. (Fig. 3.)

INVASIOK

In three casts there was evidence of extrathoracic soft-tissue masses. As mentioned, effusions were prcscnt in the corresponding pleural cavities in a11 c’ascs. (Fig. 4. )

334

FIG. present.

3.

A hilar

mass

with

a lobular

pleural

tumour

is invaded

by

and

associated

satellite

L. FIG.

4.

The

left

chest

a soft-tissue

tun~our.

lung

lesions

b

DIE‘WJSE

3:35

hIESOTMELIO~lA

HYDROPNEL”hlOTHORAS

One patient presented easily visible in this case.

with

a hydropncumothoras.

SIGNS

OF

The

pleural

tumour

was

ASRESTOSIS

Parenchymal hmg changes we’re noted in five CRSC’Salready mentioned. These vverc either nodular or fine fibrotic changes. Only modcrate changes were noted, and no evidence of progressive massive fibrosis was seen. Noncalcified pleural changes consisted of costophrenic obliteration, fissural thickening, and lamellar pleural changes. They occurred in one or other form in seven cases on the side opposite the lesion. Pleural calcification was present in two cases and has already been discussed. (Fig. 5.)

05

FIG. thelioma

5. Extensive pleural calcification is present is seen in the lower anterior mediastinum.

and

the

lobular

tumour

mass

of a meso-

The pathological behaviour of the tumour parallcls the radiological presentation of the tumour (Godwin, 1957). The mesothelioma is usually a large tumour located in pleural and peritoneal membranes. The tumour grows rapidly usually encasing the lungs and less commonly invading them. The tendency to cover the lung possibly indicates its mesothelial origin. The rarity of distant metastases is striking, particularly in view of the extensive primary mass. The tendency of certain mesotheliomas may be to invade and erode surrounding structures. This tend-

336

A. SOLOhfON

ency, however, cannot be anticipated. Penetration tinuity to the adjacent serosal cavity is common. THE

SIGNIFICANCE

OF

THE

of the diaphragm

PLEURAL

with

con-

EFFUSION

A small pleural effusion may accompany exposure to asbestos, (Sheers and Templeton, 1968) and is usually followed by resolution. Subsequent radiographs are likely to show evidence of pleural thickening. However, when radiological evidence of asbestosis is already prcscnt the appearance of a pleural effusion is not a simple expression of the asbestosis but indicates a significant complicating condition such as cancer or tuberculosis. Malignant pleural involvement products a large, often hacmorrhagic effusion. The fluid has a tendency to rapid rcaccumulation after aspiration. A mcsothelioma may also bc present with a hydropneumothorax. This may be of diagnostic aid, for, when this occurs, the tumour may be silhouetted through the pneumothorax. Indeed, it should be an csscntial prerequisite of the radiological examination to introduce a small amount of air into the pleural cavity when only a pleural effusion manifests. Routine chest radiography must then include dccubitus views to outline a possblc tumour mass. THE

SI(I:iXIFICASCE

OF

THE

HILAR

\IASS

Uncomplicated asbestosis is not associated with radiological evidence of hilar adenopathy. However, a hilar mass is not infrequently associated with mrsothelioma. The change may bc actual mcdiastinal pleural tumour, invasion of the mediastinal structures, or lymph gland involvement. The change was noted in six of the present cases, with associated pleural tumours being evident. Thus. with the knowledge of asbestos csposurt, if tuberculosis be cscludcd, a hilar mass must be considered ominous. THE

SICKIFICANCE

OF

THE

TUhIOUR

SILHOUETTE

The lobular tumour outline of a pleural mesothclioma is unlike the benign simple disc-like change of asbestosis. The lobular edge should be searched for and be detected only in profile. A lateral chest radiograph in one case was the means of detecting the subtle crenation of the mediastinal tumour mass. In another case retraction by the tumour showed the lobulated rdgc of the pleural tumour silhouetted above the diaphragm. (Fig. 6. ) THE

SIGNIFICANCE

OF

l’LEL’Ri\L

CALCIFICATIOK

The period for development of pleural calcification is 20 years. This is approximately the same period as that required for the development of mesothclioma. Only two cases in the present series showed evidence of pleural calcification. One was in a female patient born in an asbestos mining region. She had a small calcisheets of calcificafied plaque. The other patient, L‘1 male, had extensive bilateral tion. The detection of calcification will vary with X-ray technique such as penetration. No real inference can, therefore, be drawn as to the infrequency of pleural calcification in this series. However five patients older than 60 years who were born in “calcific areas” showed no calcification. It thus seems possible that the plaques that calcify are less liable to malignant degeneration. In fact, the Finnish

DIPFI’SC‘

Frc.

0.

A I~~tc~~~l chest

diow~ph

3:37

RIESOTHELIO~~A

dcmclnstrates

the eutent

of the 101~~~~~ trmumr.

C’ancc,r Hcgistvr sho\\,ccl th:lt the incidcncr of c~ncc~ of the lung and malignant pleural and peritoneal tumours is not higher in their calcification area (i.e., the endemic asbestos area of Finland ) than in other rural districts of cast Finland during the ~(WY 1953-1962; Kiviluoto came to the same conclusion ( Nero, 1968). This is in sharp contradiction to this South African series. In the present review nine patic’nts GYW ltorrl and lived for many years in “calcific areas” of South Atrica. Eighty-scvrn casrs wcrc collrcted by \I’agner. Shbggs,and hlarchand by 1961 and of these, 75 occurred in p.ltients from thr region of the Cape asbestos fklds. It may ~41 bc that among other factors, Finnish anthophyllitca seemsless harmful than South African crocidolite. TFIE

SI(:WIFIC-\NCE

OF

LUh’G

FIBROSIS

Progrrssivc fibrosis of lung tissut~ may occur as early as .3-6 years after esto :wbt~stos. Little or 110 detectable lung fibrosis need be associated with hcnign pleural changes or mesothelioma after asbestos dust csposure. In fact, there does not appe.~ to be a relationship between the severity of pulmonary asbestos& and the development of mcsothelioma. Eighteen of the cases reviewed had no significant radiological changes suggesting parenchymal fibrosis. Asbesevidcncc in the presence of sustotic fibrosis on S-ray is, however. supportiw pcctcd mcsothclinmw turnour formation. ~>OSWX~

338

A.

SOLOhlOS

Primary pleural tumours are uncommon whcrcas mctastatic cancers of this serosal surface are common, the underlying bronchopulmonary tissue most frequently being responsible. Breast neoplasms, carcinoma of the oesophogus. thoracic structure tumours, such as those of the thymus, stomach, adrenals, thyroid, and pmcrcas, are possible sources of pleural metastascs. Malignant tumours arising in the fascia of intercostal muscles, nerve sheaths, and other thoracic structures may be attributed to a pleural origin. It is imperative whenc\.er ;I pleural cancer is found, to scrutinise other sites of the body for a possible primary source. The most important and possibly the only primary malignant tumour of the pleura is the mesothelioma. Many reliable investigators have produced a large volume of literature on what they consider is an acceptable entity-primary pleural cancer. Understandable but erroneous interpretation of the histology of a notoriously pleomorphically potential tumour, has no doubt led to dissenting opinions. Many investigators do not admit the possible existence of primary turnours of the pleura. However, the radiological behaviour of diffuse pleural mcsothclioma is unlike the more commonly occurring secondary pleural neoplasms. The radiological progress of a mcsothelioma is relentless, despite treatment; lobular cncasement of the lung by the pleural tumour, associated hilar changes, or the presence of pleural evidence of asbestosis, noncalcificd or othcrwisc, should be sought. Fine, coarse, or nodular lung fibrosis. and soft-tissue> tumour masses may be the supportive evidence that could well aid the pathologist in reaching diagnostic finality. KEFEHENCES with cwnment on their relation to localized (:ollwIK. M. c. ( 1957). D’1f1 1~ nlesotheliomas: fibrous mesothe’iomas. Cancer 10, 298-319. ( 19% ). Occrlpational and “non-occupational” asbehtosis in Finland. Amer. Zndrlstr. Nono, L. Hyg. Avs. J. 29, 195-201. Effect of asbestos in dockyard workers. Brit. SHEERS, G., AND TEMPLETON, 4. H. (1968). Med. J. 3, 574-579. STUMPHIUS, J.. AND MEYER, P. B. ( 1968). Asbestos bodies and mesothelioma. Anrt. Occrcp. Hyg. 11, “83-293. WAGNER, 5. C. ( 1963). Epidemiology of diffuse mesothelial tumours: evidence of an useciation from studies in South Africa and the Vnited Kingdom. AWI. N. Y. Acad. Sci. 132, 575-578. Africa: Puthology and ExpcriWEBSTER, I. ( 1965 ) hlesothelir)~nato~~s tumors in South mental Pathology. Arln. TV. 1‘. Acad. Sci. 132, 623-646.