Gordon Stephen

L. Weisbrod,

J.

MD, FRCPC MD, FRCPC

Herman,

Thin-walled

Mark Frederick

#{149}

J. Towers,

MB, FRCR #{149} Dean W. Chamberlain, R. K. Matzinger, MD, FRCPC

#{149}

Cystic

cystic

lesions

study, were

Carcinoma’

thin-walled

identified

dation

should

include

B

(BAC)

of thin-walled with consoli-

ferent

terms:

Lung

neoplasms,

Radiology

Lung,

1992;

cysts,

60.3129,

60.3216

60.3216 185:401-405

many

are

those

lobar

atelectasis,

and

in preexisting

Cavitation,

although

cysts

uncom-

mon, may occur in single and multiple lesions (2). Isolated cases of multiple cavitary lesions in BAC have been reported (9-19). We describe four patients with proved BAC showing thinwalled cystic lesions.

CASE 1.-A

Patient

REPORTS

49-year-old

woman

with

chronic asthma developed a nonproductive cough, sore throat, and malaise over 4 weeks. Posteroanterior (PA) chest mild

radiography

showed

posterior

and

segment

in both

cystic

per

consolidation

lower

lesions

lobe

right

Multiple

present

(Fig la).

left upper size from

of the

were

(CT) showed

thick.

upper left

nodules

nodules and had cysts

in the

varied in walls only

had

thicker

walls, and some solid nodules also present (Fig ib). A chest radiograph

tamed

2 years

earlier

parenchyma

Open showed along

tent

with

BAC.

throughout was From the M.J.T., S.J.H.)

of Radiology (G.L.W., (D.W.C.), Toronto Hospital, 200 Elizabeth St. Toronto, Ont, Canada M5G 2C4, and the Department of Radiology, Ottawa Civic Hospital, Ottawa (F.R.K.M.). Received February 14, 1992; revision requested March 31; revision received April 29; accepted May 13. Address reprint requests to G.L.W. C RSNA, 1992 I

Departments and Pathology

cystic

Foci

the

evident.

walls,

copy

confirmation

allowed

A follow-up later showed

cystic

lower lesions

but

CT

seen

micros-

of the

diagno-

type). obtained of the

scans

of lung

piratory

infections

had

a known

cyst

in the right

woman

for many

thin-walled

congenital, radiography

admission, showed

PA a large,

levels tion around

cough. res-

years

and

mu!ti!ocu!ated

lung.

sumed at chest

pre-

unproductive for intermittent

The

cyst

was

pre-

having been identified 3 years previously. chest radiography thin-walled cyst

At

(Fig with

2a) air-

in the right lung. Consolidathe cyst was mainly in the

right lower lobe. Multiple, small ill-defined nodules were present in the middle and

upper

portions

some

contained

The

left lung

of the

right

central

was

lung,

areas

normal.

firmation

of a multilocular

rounding

consolidation

and

of blackness.

CT allowed cyst

with

in the

right

Multiple, small thin-walled cystic 5-15 mm in diameter were present right lung, especially in the upper (Fig 2b, 2c). Bronchoscopy biopsy of the

inflammatory with

CT repeated crease

the right ules

and

lung,

in the

was

later

and

increasing

the cyst. from the

mucus-producing cm in diameter

were

dIe lobe, and cavities measured largest genic

of these (Fig

right

upper

middle and multifo-

BAC. Cavities up to found in the mid-

in the lower

appeared 2d),

nodcon-

lobe

up to 9 cm in diameter. cyst

in

of small

lobe and resection of the right lower lobes showed widespread cal 2.5

in-

of nodules

development

around biopsy

only.

ineffective.

showed

number

left lung,

solidation A wedge

change

antibiotics

8 weeks

in size

lung. nodules in the lobe

and percutaneous needle lower lobe consolida-

right

revealed

tion

Treatment

consur-

while

to be most

The a bronchoof the

others

thought to have been due to postobstructive bronchiectasis. These were colonized to various degrees by secondary tumor

growth

appeared tumor

(Fig

to have necrosis

Follow-up months gression

(Fig

chest

after surgery of disease

2e).

formed

A few

smaller

secondary

cysts

to

20.

radiography

and

CT 7

showed marked proin both lungs. At CT,

1 year lesions.

through

demonstrated

in areas

not

Electron

CT scan progression

lobe

present

no necrosis

were

(mucus-secreting

High-resolution

right

were

lesions

material.

extend-

is consis-

of tumor

in the biopsy sis of BAC

cells

(Fig

were

lobe

which

specimen,

Cystic

lung

disease.

epithelial

alveolar

were ob-

normal

of the left upper

malignant

ing

showed

without

biopsy

up-

tomography

cystic

Some

lobe

small

in the

Computed

small

lobe; these 6 to 15 mm

1-2-mm

in the

lobes.

CT scan

28-year-old

sented with a severe She had been treated

fluid

tumor

lung

on the previous

2.-A

Patient

The

of a solitary

peripheral pulmonary nodule, multiple nodules, and lobar or diffuse conso!idation (1-6). Unusual radiographic appearances include diffuse disease with minima! or no radiographic signs, expansile pulmonary consolidation without air bronchograms,

normal

Ic, Id).

dif-

appearances.

common

developing

BAC.

produce

radiographic

most

(7,8). Index

can

been

carcinoma

RONCHIOALVEOLAR

in four

patients with proved bronchioalveolar carcinoma (BAC). The radiographic appearances are described, and possible mechanisms of formation of the lesions are discussed. Although such appearances due to BAC have rarely been described in the literature, the authors believe that the differential diagnosis cystic lesions associated

FRCPC

Lesions

in Bronchioalveolar In a retrospective

MD,

the

thin-walled that

had

Abbreviations: noma, PA

=

BAC = bronchioalveolar posteroanterior.

carci-

diAl

a.

b.

Figure

1. Patient

left upper

1.

(a) PA radiograph

lobe shows

multiple

C.

of the

small

cystic

lesions in an area of consolidation. (b) CT scans show thin-walled cystic nodules, solid nodules, and consolidation in the right lung. (c) CT scan obtained 1 year !ater and (d) high-resolution CT scans show further development of thin-walled cystic lesions in

the right

small,

lower

lobe.

thin-walled

cystic

lesions

found to have developed in areas of previous normal

Patient man had

3.-A 57-year-old a diffuse reticu!ar

ley B lines,

small

suspected

lung

asymptomatic

infiltrate,

scattered

thin-walled

were

in the right parenchyma.

Ker-

nodules,

cysts

on

and

PA

and

d.

lateral chest radiographs. Two years earher, he had undergone gastrectomy and abdominal irradiation for a small, welldifferentiated !ymphocytic lymphoma !o-

calized

to the stomach,

ment

of other Whole lung

with

no

sites. tomography

DISCUSSION

its

involve-

BAC

is defined

as a generally

well-

was confirmed from open biopsy specimens of the right upper lobe. Bone metas-

differentiated peripheral primary lung adenocarcinoma, arising beyond a grossly recognizable bronchus, with a tendency to spread on the walls of the distal air spaces, which serve as the stroma for the neoplastic cells but are not scarred as a result of the tu-

tases

mor

I-cm-diameter

showed

thin-walled

small,

cystic

nodu!es

bilaterally (Fig 3). Percutaneous fine-needle aspiration biopsy was positive for malignant

cells,

consistent

developed

therapy, was not

with

rapidly

and the patient performed.

Patient

4.-An

p!ained malaise

BAC.

despite

chemo-

died.

Autopsy

82-year-old

woman

consolidation

in the

lung.

No improvement

with

seen.

Sputum

right

com-

lower

antibiotics

cytology

was

suspicious

for adenocarcinoma, and transbronchia! biopsy revealed adenocarcinoma spreading along the alveolar walls, which is consistent graphs

with BAC. Follow-up obtained 7 months

progression

of disease,

chest radiolater showed

with

involvement

of the previously normal left lung. Multipie, small, thin-walled cystic lesions with intervening

consolidation

cysts

had

died

of respiratory

ter.

Autopsy

402

#{149}

developed was

Radiology

not

between (Fig

4). The

failure

shortly

performed.

(20).

The

presence

adenocarcinoma

of a nonproductive cough and for I month. PA chest radiography

showed was

BAC

the patient

thereaf-

incidence

is said

Smoking

of a primary

elsewhere

the

in the

cell of origin

has been resolved by the electron microscopic findings that BAC represents a heterogeneous group of tumors that may arise from type II pneumocytes, nonciliated bronchiolar

(Clara) cells, or mucus-producing bronchiolar cells, or perhaps bronchiolar

entiation BAC primary

stem

into any represents pulmonary

cell

capable

from

In

contrast

neoplasms,

the

women

with

commonly monary

a

of differ-

of these (2,4,15,21). 1.S%-6.S% of all neoplasms, and

primary of BAC

cancer

form

lung in

is high in those

of disease

commonly

of pul-

appears

as a single

with

(6). BAC

develops in areas fibrosis (4,21,22).

most

(6).

associated

particularly

the localized

BAC

be rising

to other incidence

lung

(30%-5O%),

diographically

body precludes the diagnosis, because metastatic spread can produce an identical histologic appearance. The issue of unifocal versus multifoca! ori-

gin is not settled. Controversy about

(21).

to

is not strongly

ra-

pulmonary

nodule, multiple nodules, or single or multiple areas of consolidation (1-6). The solitary nodule form is slow growing, and mediastina! adenopathy and recurrence following removal are unusual, resulting in an excellent prognosis. In contrast, the diffuse form of the disease is relentlessly progressive,

and

vivors,

there

are

regardless

Atypical

few

long-term

of intervention

radiographic

sur-

(6,23).

appearances

of BAC include lobar atelectasis, expansile consolidation without air bronchograms, elongated lobulated opacity

and graphs

resembling

apparent with

on CT scans

mucoid

normal diffuse

chest disease

or at surgery

impaction,

radioevident

(7). November

1992

a.

d. Figure around

2. Patient the cyst

2.

(a) PA chest

in the

right

lower

b.

C.

e.

f.

radiograph shows a large, thin-walled cyst with air-fluid levels in the right lung. Consolidation lobe. Multiple, small, ill-defined nodules are present in the middle and upper portions of the

some contain central areas of decreased opacity (arrowhead). (c) a thin-walled mu!ti!oculated cyst with surrounding nodules, eosin stain; original magnifications, by malignant epithelium (curved lined by malignant epithe!ium.

x63) arrow), (1) Necrosis

show mechanisms and residual benign in a tumor nodule

Cavitation

in BAC is unusual because of the relative lack of necrosis (22) and the tendency of the tumor to preserve normal lung architecture (1 5). Cavitation occurred in 7.4% of patients (10 of 136 and nine (2,15,21,24),

of 122

patients)

in two

large

series

(1,25). Of 100 cavitary bronchogenic carcinomas reported by Chaudhuri, three were alveolar carcinomas (26). Cavitation in BAC may occur in single or multiple lesions (2). The wall thickness of the cavitary lesion is usually thick but may be thin (24,27). Intracavitary

BAC

is rare

aspergilloma

A radiographic tation can occur in several

appearance in association ways.

Preexisting

(28).

of caviwith lung

cysts

such

2d) (7,8), bronchiectasis), interstitial

(b, c) At CT, (b) thin-walled one showing of cavity formation ciliated epithelial (arrow).

cystic and solid nodules in the right upper lobe and cavitation, are evident. (d-f) Photomicrographs (hematoxy!inassociated with BAC. (d) A bronchogenic cyst is partially lined lining is indicated (straight arrows). (e) A bronchiectatic airway

as bronchogenic postinflammatory

cysts

(Fig

ular

cysts

(ie,

(4,5).

“honeycombing” fibrosis and healed

in granu-

lomatous disease, postinfarction cysts, and emphysematous bullae may antedate the development of malignancy

(29) and

may

be secondarily

cob-

nized by tumor growth. Their role (if any) in tumor pathogenesis is controversial. A radiographic appearance in which small areas of blackness within the lesion suggest cavitation can occur. These represent areas of focal emphysema

is present right iung

secondary

tion (29) or areas rendered airless,

to scar

retrac-

of normal lung not because of the irreg-

lepidic growth of the neoplasm Kuhlman et al (30) described

findings

of pseudocavitation

of solitary small,

oval

mimicking

BAC

in which

multiple,

areas

of low

attenuation

tiny

cavities

CT

in cases

were

seen

within or surrounding the periphery of the mass. The CT appearance of pseudocavitation may reflect the same process that gives rise to the air bronchogram

on

plain

radiographs:

the propensity of the tumor to proliferate along the walls of the alveolus without disrupting the overall lung architecture and with preservation of bronchiolar patency (29). Zwirewich et al (31) described bubblelike areas of air attenuation in 25% of malignant

nodules, type,

most

commonly

of the

at high-resolution

CT.

BAC

At patho-

logic evaluation, these corresponded either to patent small bronchi within the nodule or cystic spaces within papillary regions of tumor growth. True cavitation may occur secondary to tumor growth through ischemic necrosis (Fig 20. Necrosis within larger tumor nodules is usually ascribed to outgrowth of the blood supply to the center of the lesion, but this is unusual because the unique nondestructive growth pattern of BAC usually preserves perfusion to the involved area of lung. Diffuse BAC with multiple bilateral cavities has rarely been described (919). Interestingly, reports of this disease The

have lesions

mostly can

both

tomography

scans

of right

and

left

upper

lobes

show

small

come from Japan. be small, and the

walls can be remarkably thin (2,12,15). Ohba et a! (12) reported a 47-year-old woman in whom chest radiography showed bilateral, diffuse reticulonodular infiltrates with multiple cysts 3-10 mm in diameter and numerous small nodules with central pinholes. At autopsy, there was bilateral cystic destruction of the pulmonary parenchyma. The cystic spaces had two patterns: (a) carcinomatous cavities and (b) emphysematous cysts with less carcinoma in the wall. The pathogenesis of cyst formation was considered to be due to two main mechanisms: central necrosis within the nodule and, more commonly, check-valve obstruction at the terminal bronchiobar level. Thickened fibrous terminal bronchioles were found in some sections, which could account for the check-valve obstruction and formation of emphysematous cysts. Imai et a! (ii) reported a 70-yearold man who died of diffuse BAC. At autopsy,

Figure 3. Patient 3. Conventional thin-walled cystic nodules.

lungs

were

filled

with

Figure 4. Patient ing consolidation.

4.

PA

chest

radiograph

shows

diffuse

bilateral

cystic

lesions

with

interven-

disseminated whitish tumors accompanied by multiple cysts. Microscopically,

the

cysts

resembled

centrilobu-

bar emphysema. Histologically, the cysts were due to distended alveoli filled with abundant mucus. The walls were composed of BAC. Bronchiectasis was found in some areas. The authors suggested that tumor cells

extending

along

the

alveolar

walls destroyed the alveoli centribobu!ar emphysematous No

radiographs

The patient sions opsy.

were

cause of the 1 is uncertain

to form cysts.

shown.

cystic lesions in because the be-

were not revealed at lung biWe can only speculate that the

thicker-walled cystic nodules and the cysts arising in consolidated lung were due to ischemic necrosis resulting from tumor growth. The thinAn.,

walled cysts in the left upper lobe and those that subsequently developed in the right bower lobe were not present on previous chest radiographs or CT scans

and

could

be

due

to check-valve

terminal bronchiolar obstruction as proposed by Ohba et a! (12) or possibly cystic spaces within papillary regions

of tumor

growth.

The

barge

multibocubar cyst in patient 2 predated the BAC by at beast 3 years and likely represented a congenital bronchogenic cyst secondarily colonized by tumor growth (Fig 2d). The smaller cystic lesions presumably arose secondary to tumor growth through ischemic necrosis (Fig 20 and postobstructive bronchiectasis (Fig 2e). It is possible that air-containing cystic

spaces within papillary regions of the tumor contributed to the appearance. The lung biopsy in patient 3 did not reveal cavitary lesions, so their pathogenesis can therefore only be presumed to be similar to that of the besions in patient 1. Similarly, the cause of the cavitary lesions in patient 4 remains unproved. The differential diagnosis of multiple thin-walled cystic lesions in the lung includes congenitab causes (cystic adenornatoid malformation, bronchogenic cysts), airway diseases (bronchiectasis, bulbous emphysema), infections (tubercubous, fungab, hydatid cysts, pneumatocebes), emboli (septic, nonseptic), neoplasms (metastases, lymphoma, baryngeal

papillomatosis),

autoimmune

November

1992

diseases

(Wegener

9.

granulomatosis,

uborna),

causes nia)

trauma,

(congenital (32).

With

and

gran-

miscellaneous

diaphragmatic thin-walled

10.

her-

cystic

le-

sions, particularly if associated with consolidation, BAC should be a diagnostic consideration. U

11.

12. Acknowledgment: for her assistance manuscript.

We thank Rose in the preparation

Baldwin of this

13.

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3.

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