Imaging of Pleural

Manifestations Tumors1

Mary C. Dynes, MD E. Maureen White, MD WillardA. Fry, MD Gaty G. Ghahremani, MD

radiologic assessment of pleural tumors may be accomplished with several imaging modalities, the standard noninvasive techniques include chest radiography and computed tomography (CT) These examinations may be supplemented with magnetic resonance imaging and occasionally with ultrasound. Depending on the location, size, and underlying histologic features, pleural tumors may produce a spectrum offindings. CT is particularly useful in defining the location and extent of these masses. The authors present a review of basic pleural anatomy and imaging features of both benign and malignant pleural neoplasms. The pleura may be involved by one of severa! primary or metastatic tumors. Specific cell types are diffuse malignant mesothelioma (the most common plain radiographic findings are unilateral pleural effusion and pleura! thickening), localized fibrous tumor (circumscribed, spherical or ovoid, noncalcified lesions arising in the pleural surface), metastatic disease (radiographic findings may mimic those of malignant mesothelioma), and uncommon neoplasms including thymoma and lymphoma. Among these various pleural liimors, metastatic disease represents the most common neoplasm.

Although

.

U

INTRODUCTION

Radiologic

assessment

of pleural

tumors

may

be

achieved

with

several

imaging

tech-

niques. The standard noninvasive evaluation includes chest radiography and computed tomography (CT) and may be supplemented with magnetic resonance (MR) imaging and occasionally with ultrasound (US) (1). The radiographic features of pleural abnormalities, including calcification, are usually well demonstrated on CT scans. CT is particularly useful in distinguishing pleural from peripheral pulmonary lesions

Index 66.317,

and

in defining

terms:

Lymphoma,

66.32,

I

From

McGaw assembly. requests C RSNA,

1992;

the

66.34

#{149} Pleura,

66.33

RadloGraphics

and

#{149} Mesothelioma,

radiography,

of Diagnostic

Center

Received

location

extent

#{149} Pleura,

66.3254

ofpleural

masses.

CT,

#{149} Pleura,

66.1211

neoplasms,

66.31,

66.3

15,

66.11

12:1191-1201

Departments

Medical

the

March

of Northwestern 19,

1992;

Radiology

(MCD.,

University, revision

requested

2650

E.M.W., Ridge April

G.G.G.) Aye,

28 and

and

Evanston, receivedjuly

Surgery IL 60201.

(W.A.F.), From

7; acceptedJuly

Evanston the

1991

HospitalRSNA

8. Address

scientific reprint

to E.M.W. 1992

1191

Figure 1. and solitary

D,ffuse

pleural

tumor

infiltration

Pleural

effusion

Diffuse

pleural

tumors. (a) Coronal diagram shows diffuse pleural disease

a.

on the left side of the chest and a solitany pleural

mass

in

the right

hemithoi-ax. (b) Transverse diagram demonstrates disseminated nodular pleural iiimon with effusion in the left hemithorax and a focal right pleural mass. b.

Pleural tumors typically appear as well-defined soft-tissue masses, with angles obtuse to the chest wall (2). These neoplasms may be focal or diffuse and may be associated with pleural effusion. Although there is overlap in the radiologic manifestations of benign and malignant tumors, certain features assist in

this

distinction.

lesions,

appears ulated

1192

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RadioGraphics

U

Dynes

et a!

For

example,

in diffuse

malig-

nant pleural disease, findings suggestive of a neoplastic process include circumferential pleural thickening, disseminated pleural nodularity, a panietal pleural thickness exceeding 1 cm, and mediastinal pleural involvement (3). In contrast to diffuse malignant pleural the

localized

fibrous

tumor

as a solitary, well-circumscribed, soft-tissue mass arising from

Volume

12

usually

the

lobpleu-

Number

6

ral surface (Fig 1). Despite these features that typify benign and malignant pleural neoplasms, definitive diagnosis almost invariably requires biopsy. Among the various pleural tumors, metastatic disease represents the most common neoplasm. Primary tumors account for less than 5% of pleural neoplasms. Specific histopathologic types of tumors originating in the pleura include diffuse malignant mesothelioma, localized fibrous tumor, and uncommon neoplasms such as primary pleural lymphoma. This article presents a review of basic pleural anatomy and imaging features of both benign and malignant pleural neoplasms.

peripherally into internal mammary and intercostal lymph nodes, as well as into mediastinal lymph nodes. Lymph from the visceral pleura flows centripetally toward the hila (4). U

PLEURAL

.

Diffuse

Diffuse

NEOPLASMS

Malignant

Mesothelioma

malignant

is a rare

mesothelioma

tumor,

with

of the

a prevalence

pleura

of approxi-

mately 2,000-3,000 cases per year in the United States (7). There is a strong association between the development of this neoplasm and asbestos exposure; approximately 5%-7%

of asbestos

malignant

workers

mesothelioma.

develop

The

latent

diffuse

period

NORMAL PLEURAL ANATOMY The visceral and parietal pleurae are serosal membranes of mesodermal origin that line the pleural space. The visceral pleura invests the lungs and intenlobar fissures, whereas the parietal pleura covers the ribs, diaphragm, and mediastinum. These two layers of pleurae are continuous at the pulmonary hila and are

disease usually ranges between 30 and 45 years. Approximately two-thirds of patients with the diagnosis of diffuse malignant mesothelioma are 50-70 years of age, with a two to six times higher prevalence in men cornpared with that in women (8). The most common plain radiographic find-

reflected

ings

U

mnferiorly

double fold to ligament. The lines represent faces from the The pleural

toward

the diaphragm

as a

form the inferior pulmonary anterior and posterior junction apposition of the pleural surright and left hemithoraces (4). membrane includes both the

mesothelium and a thin layer of mesenchymal connective tissue. Mesothelial cells are generally flat or cuboidal. Below the thin cellular layer, there is a thicker zone of connective tissue

containing

blood

vessels

lymphatic (5).

The

blood

channels

supply

and

to the

panietal pleura is provided by systemic yessels, whereas the visceral pleura is perfused predominantly by the pulmonary circulation, with some bronchial contribution (6). Lymphatic drainage of the parietal pleura flows

November

1992

between

initial

in diffuse

exposure

malignant

and

onset

mesothelioma

of clinical

are

unilateral pleural effusion (30%-95%) and pleural thickening (8). Solid pleural lesions vary from focal masses to diffuse thickening surrounding and encasing the entire lung surface. Extension into the intenlobar fissures is common, occurring in 40%-86% of patients (9). Distinct pleural masses without effusion are identified in less than 25% of patients on their initial chest radiograph (8). Benign calcifled or noncalcified plaques may be present. Rib destruction is a complication of advanced bulky

disease.

Dyneseta!

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RadioGraphics

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1193

a. Figure

b. 2.

Diffuse

malignant

pleural

mesothelioma.

(a) Posteroanterior

chest

radiograph

shows

diffuse

cm-

cumferential nodular pleural thickening (arrows), with extension to the mediastinal pleura and fissures, encasing the right lung. (b) CT scan demonstrates the irregular pleural thickening (solid arrows) along the costal and mediastinal pleural surfaces, with extension into the major fissure (open arrow).

CT is superior in evaluating

pleural pears

to conventional the

extent

mesothelioma. with widespread

(Fig

2).

radiography

of diffuse

This tumor often nodular thickening

Characteristically,

both

the

and parietal pleurae are involved zen’ mediastinum of the involved has been thought to be a diagnostic malignant

mesothelioma.

either ipsilateral cur, the latter sion

or bulky

or contralateral as a result of large mass

(Fig

3).

ap-

high

visceral

(5).

A “fro-

hemithorax

‘

diffuse

described the tumor

malignant

feature of However, shift may ocpleural effu-

Approximately

20%

of cases demonstrate pleural calcification (Fig 4). CT is helpful in demonstrating unsuspected abdominal extension of tumor and in identifying

metastatic

disease.

particularly in the useful in assessing as well

infiltration. features

1194

U

RadioGrapbics

as chest

wall

Previous of malignant

U

MR

imaging,

coronal plane, may also mediastinal involvement, and

abdominal

reports regarding mesotheliomas

Dynes

et a!

tumor

MR have

be

intermediate on Ti-weighted

signal

intensity

(10). Once malignant nosed, the typical to death, usually survival

time

after

signal intensity images and

on

within slightly

T2-weighted

images

mesothelioma course is rapid oflocal disease.

is diagprogression The mean

diagnosis

is approximately

1 1 months (8). Two surgical approaches are currently employed. Extrapleural pneumonectomy is performed in patients with tumor confined to the affected hemithorax, with resection

of ipsilateral

pleura,

lung,

pericar-

dium, and diaphragm. This is a technically difficult operation with considerable morbidity and mortality and is reserved for patients with

adequate

pulmonary

reserve

and

no

con-

traindication to surgery (1 1). A parietal pleurectomy may be performed as a palliative procedure in patients with more advanced disease (7). External beam irradiation and chemotherapy have also been used with minimal success. Despite several therapeutic options,

it remains

ment (8).

substantially

unclear

whether

alters

any

the

dismal

Volume

12

treat-

prognosis

Number

6

Figures 3, 4. the right lower

Diffuse malignant hemithorax. (3b)

mass occupying

the

(4a)

of a different

CT section

soft-tissue

right

thickening

tamed

through

fissure,

with

. Localized Previously

side

small

patient

(arrows)

the lower

Fibrous known

mesothelioma.

oven

demonstrates

calcified

pleural

of the thorax

costal

mediastinal

pleural plaques

mesotheliomas,

tumors of the pleura are found in all age groups, over 50% of cases are encountered in patients during the 6th and 7th decades oflife (12). There gender

predilection.

quently asymptomatic, discovered incidentally About 80% oflocalized

nate in the visceral

November

1992

Patients

are

radiograph

the middle

rare. Although

is no

chest

fre-

right

effusion

shows

opacification

of

chest CT scan shows a lange mnhomogeneous contralateral shift of mediastinal structures.

through

fibrous

localized

Frontal

the

Tumors

localized

as

(3a)

material-enhanced chest, with a slight

obtained

extending

chest

bilateral

pleural

Contrast of the lower

and

in the right

shows pleura.

lower

irregular (4b)

hemithorax,

lobulated

CT section

extending

ob-

into

a

(arrows).

20% in the parietal pleura (13). An increased prevalence of hypoglycemia (4%) and pulmonary osteoarthropathy (35%) has been reported There asbestos mors.

in patients with is no recognized exposure

and

these tumors (14). association between localized

fibrous

iii-

with the tumor being on chest radiographs. fibrous tumors origipleura and the remaining

Dynes

et a!

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RadioGrapbics

U

1195

a.

b.

.,.-

. r.i’ d.

C.

Figure

:

5.

Localized

fibrous

tumor.

(a) Postenoantenion

chest

radiograph

shows

a soft-tissue

mass

(arrow)

superior to the aortic arch simulating a mediastinal mass. (b) Coronal Ti-weighted MR image (spin echo 600/20 [repetition time msec/echo time msec]) of the posterior chest shows the mntermediate-signal-mntensity mass (arrow) arising from the pleura. (c) Tnansaxial T2.weighted MR image (spin echo 2,000/80), obtamed 2 cm above the aortic arch, demonstrates high signal intensity within the pleural mass (arrow). (d) dunculated tumor (arrow) arising from the visceral pleural surface is seen intraoperatively.

Localized fibrous tumors are circumscribed, spherical or ovoid, noncalcified lesions that arise in the pleural surface. The size may range from less than 2 cm to 30 cm. Localized fibrous tumors are usually solitary masses and are often pedunculated (Fig 5). As a consequence, these lesions may demonstrate changes in position and shape during fluoroscopy (15). The classic radiographic findings of pleural or extrapleural masses may be identifled. These include incomplete visualization of the tumor margins and sharp delineation of

the mass

1 196

U

RadioGraphics

on

tangential

U

Dynes

images

et a!

(Fig

6a,

6b).

Another sions,

that

finding the

obtuse

is typical

angle

of the

Pe-

of pleural

le-

mass

the

with

chest wall, is not always observed in localized fibrous tumors. A more common feature of these neoplasms is smooth tapered margins between the mass and pleura (15). On CT scans, localized fibrous tumors usually appear as a well-defined, is particularly

lobulated

useful

ing

in the

intenlobar

late

a parenchymal

pleural

in identifying fissures,

lesion

which

(Fig

mass.

CT

masses 6c)

may

(16).

arissimu-

MR

features of localized fibrous tumors include low signal intensity on Ti-weighted images and high signal intensity on T2-weighted images, likely reflecting the high cellularity of these tumors (Fig 5c).

Volume

12

Number

6

Figure 6. Localized fibrous tumor. (a) Posteroanterior chest radiograph demonstrates an abnormal, ill-defined soft-tissue opacity (arrow) at the right cardiophrenic angle. (b) Lateral chest diograph shows the soft-tissue opacity

(arrow)

in the major

sharply defined trast to its poor

anterior pleural

view. mass.

fissure.

border

Note

of the

mass

ra-

the in con-

definition in the postenoThis is characteristic of a (c) CT scan

obtained

with

lung window setting demonstrates the elongated ovoid mass (solid arrow), with beaking at both ends, oriented within the major

Localized

fibrous

tumors

of the

pleura

are

believed to originate from submesothelial mesenchymal cells rather than from the mesothelial lining cells. Thirty-seven percent of all localized fibrous tumors are histologically malignant. However, approximately half of the histologically malignant tumors and all of the benign lesions may be successfully managed with surgical excision. Operative resectability

is the

cal outcome

November

most

important

predictor

. Pleura! Metastatic ity

of pleural

fissure

(open

Metastases disease accounts neoplasms.

arrows).

for the Approximately

vast

major40%

of pleural metastases arise from lung carcinoma, 20% from breast carcinoma, 10% from lymphoma, and the remaining 30% from other primary sites (4).

of clini-

(12).

1992

Dynes

et a!

U

RadioGraphics

U

1197

d.

C.

Figure diograph extensive

ulated lower defect tension

7.

Treated invasive thymoma with recurrence in both pleural spaces. (a) Posteroanterior chest rashows bilateral diffuse pleural thickening (arrows). In the night hemithonax, the thickening is more and lobulated, encasing the night lung. (b) Contrast-enhanced CT scan demonstrates bilateral lob-

pleural masses (arrows) with both solid and fluid components. (c) CT section obtained through the chest shows a large complex mass along the diaphragmatic pleura on the right side. A low-attenuation (arrow) in the right atrium represents a tumor thrombus. (d) CT scan shows a subdiaphragmatic exof malignant

thymoma,

with

tumor

thrombus

Invasive thymoma is an uncommon thoracic primary neoplasm with a propensity for pleural extension. This pleural implantation results in either widespread pleural thickening or multiple discrete masses. Invasive thymoma may be radiographically indistinguishable from mesothelioma, particularly when the anterior mediastinal tumor component of the thymoma is relatively small. Extrathoracic metastases from invasive thymoma occur in-

(arrow)

in the

inferior

vena

cava.

frequently. However, infradiaphragmatic tension may lead to invasion of the dominal cavity, and retroperitoneum

exliver, ab(Fig 7)

(17).

tumors

Several

may metastasize ovarian, uterine, atic

carcinoma,

extrathoracic

primary

to the pleura. gastrointestinal,

as occasional

sarco-

mas. When there is no recognized tumor, metastatic adenocarcinoma pleura may be difficult to diagnose

primary to the because

its histologic

as well

These include and pancre-

similarity

to malignant

of

mesothe-

lioma.

Histochemistry, immunohistochemisand electron microscopy may be necessary for differentiation (5). Radiographic try,

1 198

U

RadioGraphics

U

Dynes

et a!

Volume

12

Number

6

8.

9b

9a. Figures tially

8, 9. loculated

to the major radiograph

(8) Pleural

metastases

left pleural

effusion

fissure

on the left side

demonstrates

from and

several

from

a soft-tissue

9c bronchogenic

primary

a primary

mass

carcinoma.

pleural-based

with

tumor

lower-extremity an ill-defined

of pleural metastases may mesothelioma. Malignant

is the

most

static

pleural

frequent disease

manifestation and

is often

also mimic effusion of metaaccompa-

nied by solid tumor deposits ofvariable size (Fig 8) (4). Metastatic pleural lesions may also appear as a solitary implant on the costal, diaphragmatic, or mediastinal pleura or within the

interlobar

November

fissures

1992

(Fig

.

(arrows).

fibrosarcoma. superolatenal

Pleura!

demonstrates (9)

Pleural

a parmetastasis

(a) Posteroanterior

bonder

hemithonax. (b) Lateral chest radiograph demonstrates a well-defined ovoid ented along the major fissure. (c) CT scan obtained at the level of the aortic arrow) along the superior major fissure (open arrow) on the left side.

findings malignant

CT scan

nodules

in the

middle

mass with tapered arch demonstrates

chest of the

left

margins ona mass (solid

Lymphoma

Involvement of the pleura by lymphoma occurs in both Hodgkin and non-Hodgkin disease. The lymphomatous deposits arise from lymphatic channels and lymphoid aggregates in the

subpleural

connective

tissue

below

the

9).

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et a!

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RadioGraphics

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1199

a. Figure 10. Pleural lymphoma. chest radiograph shows irregular

b. (a) Frontal left pleural

thickening (arrows). (b) Concurrent CT scan demonstrates diffuse pleural thickening (arrows) greater than 1 cm in thickness, involving

the left mediastinal and costal pleura. (c) Follow-up CT scan obtained after chemotherapy shows almost complete resolution of the pleural tumor.

C.

visceral sion

pleura

(18).

is uncommon.

True

visceral

Radiographically,

pleural

inva-

solid

pleural lymphoma appears either as a solitary nodule or as diffuse tumor infiltration (Fig iO) (18). Associated pleural effusion is attributed to obstruction of lymphatic channels by mediastinal lymphadenopathy (19). Although primary pleural lymphoma as the only initial site of malignancy is rare, lymphomatous involvement of the pleura not uncommonly occurs secondarily.

In this

circumstance,

it appears

associated with mediastinal or pulmonary parenchymal velops as a manifestation (18). U

SUMMARY

Noninvasive

ing

histopathologic in the

mesothelioma,

uncommon ral lymphoma.

U

RadioGrapbics

U

Dynes

et a!

evaluation

of pleural

tumors

is

generally accomplished with chest radiography and CT and may be supplemented with MR imaging and occasionally with US. Among the various pleural tumors, metastatic disease represents the most common neoplasm. Specific

1200

lymphadenopathy lymphoma or deof recurrent disease

pleura

types include localized

neoplasms

of tumors

originat-

diffuse

malignant

fibrous

tumor,

such

as primary

Volume

12

and

pleu-

Number

6

U

1.

12.

REFERENCES

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et a!

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