AJR 2002; 178:1208-1210
© American Roentgen Ray Society
Intimal Sarcoma of the Pulmonary Arteries Seen as a Mosaic Pattern of Lung Attenuation on High-Resolution CT
Carole J. Dennie1,
John P. Veinot2,
David G. McCormack3 and
Frasen D. Rubens4
1 Department of Diagnostic Imaging, The Ottawa Hospital, University of Ottawa,
1053 Carling Ave., Ottawa, Ontario K1Y 4E9, Canada.
2 Department of Laboratory Medicine, The Ottawa Hospital, University of Ottawa,
Ottawa, Ontario K1Y 4E9, Canada.
3 Division of Respirology, London Health Sciences Centre-Victoria Campus, 375
South St., London, Ontario N6A 4G5, Canada.
4 Division of Cardiac Surgery, University of Ottawa Heart Institute, 40 Ruskin
St., Ottawa, Ontario K1Y 4W7, Canada.
Received November 27, 2000;
accepted after revision November 21, 2001.
Address correspondence to C. J. Dennie.
Introduction
The mosaic pattern of lung attenuation on high-resolution CT is
characterized by areas of increased and decreased attenuation. It is
nonspecific and can be caused by infiltrative lung disease, airway disease, or
vascular disease. When the pattern is due to vascular disease, the areas of
inhomogeneous lung density are sharply demarcated by the edges of secondary
pulmonary lobules. The areas of increased attenuation are attributed to blood
flow redistribution. In these areas, the vessels are increased in size and
number. The areas of decreased lung attenuation are attributed to vascular
occlusion, and in these areas, the vessels are smaller and less numerous
[1]. In most cases of vascular
disease leading to mosaic perfusion on high-resolution CT, the cause is
chronic thromboembolic pulmonary artery hypertension. This pattern has rarely
been seen in patients with primary pulmonary artery hypertension, pulmonary
capillary hemangiomatosis [1],
pulmonary venoocclusive disease
[1], polyarteritis nodosa
[2], and scleroderma
[3]. It has also been reported
in one case of valvular heart disease, in a left-to-right shunt, and in
fibrosing mediastinitis
[3].
We present two cases of intimal sarcoma of the pulmonary arteries with
clinical and CT findings identical to those of chronic thromboembolic
pulmonary hypertension, including a mosaic pattern of lung attenuation.
Case Reports
A 34-year-old woman presented with a 2-year history of progressive
shortness of breath. She had no history of deep venous thrombosis, pulmonary
embolism, or other medical problems. Her dyspnea worsened significantly 3
weeks before admission, and she also developed cough syncope and
hemoptysis.
A chest radiograph showed enlargement of the right ventricle and left
pulmonary artery. A transthoracic echocardiogram showed severe pulmonary
artery hypertension. Contrast-enhanced helical CT of the chest revealed
filling defects in the right and left pulmonary arteries
(Fig. 1A) as well as in several
segmental and subsegmental arteries (Fig.
1B) and rapid tapering of the right interlobar artery.
High-resolution CT of the thorax depicted a mosaic pattern of lung attenuation
consistent with chronic thromboembolic pulmonary hypertension
(Fig. 1C). No pulmonary nodules
were seen.
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Fig. 1A. —34-year-old woman with increasing shortness of breath due to
pulmonary artery sarcoma. Contrast-enhanced helical CT scan obtained at level
of right pulmonary artery shows triangular mural filling defect
(arrows) at bifurcation of main pulmonary artery. Defect extends
along posterior wall of right pulmonary artery, and left interlobar artery is
enlarged.
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Fig. 1B. —34-year-old woman with increasing shortness of breath due to
pulmonary artery sarcoma. Contrast-enhanced helical CT scan obtained at level
of aortic arch shows filling defects (arrows) in segmental and
subsegmental arteries to left upper lobe.
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Fig. 1C. —34-year-old woman with increasing shortness of breath due to
pulmonary artery sarcoma. High-resolution CT scan obtained at level of aortic
arch shows regions of decreased attenuation (arrows) in which vessels
are smaller.
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On admission, the patient could not lie supine, and obtaining a pulmonary
angiogram was not possible. She was taken to the operating room for pulmonary
thromboendarterectomy because she was developing hemodynamic compromise.
Endarterectomy was performed under deep hypothermic circulatory arrest, using
standard techniques [4]. Both
pulmonary arteries were explored, and extensive specimens were removed.
Several attempts were made to discontinue cardiopulmonary bypass, but right
heart failure developed due to severe pulmonary hypertension. Extracorporeal
membrane oxygenation was initiated, and a pulmonary angiogram was obtained
revealing persistent obstruction of the right upper and middle lobe arteries.
The patient was returned to the operating room, where the right pulmonary
artery was reexplored, but no further material could be removed.
When the final pathologic results revealed intimal sarcoma of the pulmonary
artery as the cause of this patient's pulmonary artery hypertension,
extracorporeal membrane oxygenation was discontinued and the patient died.
The second patient was a 64-year-old woman with a history of breast
carcinoma and chest wall radiation, who presented with a 4-month history of
progressive dyspnea and atrial fibrillation. Contrast-enhanced helical CT of
the chest showed filling defects in the pulmonary artery circulation (Figs.
2A and
2B). High-resolution CT
revealed a subtle mosaic pattern of perfusion that was most evident in the
right upper lobe, suggesting the diagnosis of chronic thromboembolic pulmonary
hypertension (Fig. 2C).
Although the radiologic findings were similar to those of the first patient
with intimal sarcoma, this diagnosis was not considered preoperatively.
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Fig. 2A. —64-year-old woman with intimal sarcoma of pulmonary artery.
Contrast-enhanced helical CT scan obtained at level of left pulmonary artery
depicts large filling defect (arrows) in left pulmonary artery
extending into left upper lobe and interlobar arteries.
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Fig. 2C. —64-year-old woman with intimal sarcoma of pulmonary artery.
High-resolution CT scan obtained through right upper lobe shows regions of
decreased attenuation (arrows) in which vessels are smaller.
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The patient was taken to the operating theater for pulmonary
thromboendarterectomy. However, the gross nature of the resected specimen was
suggestive of a malignant tumor rather than of an endothelial blood clot.
Despite this complication, the patient was successfully weaned from
cardiopulmonary bypass and recovered uneventfully.
The surgical specimens consisted of soft tan branching masses that
resembled casts of pulmonary arteries. Specimens from both patients were
similar to other pulmonary artery thromboendarterectomy specimens but had
mucoid regions, and in the second case, firm cartilaginous areas. Microscopic
examination revealed the specimens to be poorly differentiated intimal sarcoma
of the pulmonary artery. The entire cast of specimens was composed of tumor
with extensive arborization. The tumors were mixed with small amounts of
organizing thrombus, but the thrombotic component was not prominent. In the
second patient, the firm areas were chondrosarcomatous differentiation of
malignant cartilage tissues.
Discussion
Primary intimal sarcomas of the pulmonary artery are rare tumors that are
most commonly diagnosed at surgery or autopsy. Most patients present between
the ages of 45 and 55 years with a 2:1 female—male ratio. Dyspnea, chest
pain, and cough as well as hemoptysis are common presenting symptoms. The most
common antemortem diagnosis is acute pulmonary thromboembolism, but other
entities such as pulmonary arteritis, pulmonary hypertension, and lung
carcinoma are often considered
[5]. The prognosis is poor,
with a mean survival rate of 12 months after the onset of symptoms
[6].
Pulmonary artery sarcomas generally arise from the intimal layer of the
right, left, and main pulmonary arteries and extend as polypoid masses into
the small pulmonary arteries
[5,
6]. Less commonly, they grow in
a retrograde fashion to involve the pulmonary valve and right ventricle
[5,
6]. In approximately 50% of
patients, the tumors spread transmurally into adjacent lung, bronchial wall,
or lymph nodes, and extension to myocardium and mediastinum has also been
described. The most common site of distant metastases is the lung
[5].
The radiologic findings of pulmonary artery sarcoma depend on the size of
the tumor. If the tumor is large enough to distend an artery but remains
intraluminal, it will present as a unilateral hilar mass that may project into
pulmonary parenchyma in an arterial distribution. There may be associated
distal oligemia. If the mass extends transmurally into adjacent lung, it
mimics bronchogenic carcinoma. If the mass is intraluminal and does not
distend the artery, findings on the chest radiograph may be normal
[7].
On pulmonary angiography, the distinction between tumor and thrombus may be
possible when the polypoid intraluminal filling defects move with the cardiac
cycle [5]. Otherwise, the
findings are nonspecific and mimic pulmonary thromboemboli.
Contrast-enhanced CT shows filling defects in the pulmonary arteries that
are indistinguishable from acute or chronic pulmonary emboli. On
high-resolution CT, our patient presented with a mosaic pattern of lung
attenuation that was indistinguishable from chronic thromboembolic pulmonary
artery hypertension. We postulate that this was due to direct tumor growth
into small pulmonary arteries or tumor emboli occluding small peripheral
vessels. This pattern is a newly described vascular cause of inhomogeneous
lung density.
Gadolinium-enhanced MR imaging of the pulmonary arteries is diagnostic of
tumor rather than of blood clot if the diagnosis is considered preoperatively,
because vascularized tumor enhances, whereas nonvascularized intraluminal
blood clot does not [8].
In summary, intimal sarcoma of the pulmonary artery should be considered in
the differential diagnosis of chronic thromboembolic hypertension.
Contrast-enhanced helical CT findings of filling defects in pulmonary arteries
and high-resolution CT findings of a mosaic pattern of lung attenuation can
resemble chronic thromboembolic hypertension. Distention of pulmonary arteries
by filling defects should alert the radiologist to the possibility of tumor
rather than blood clot and should prompt gadolinium-enhanced MR imaging.
Furthermore, if the diagnosis of intimal sarcoma is not made before
surgery, it should be considered in patients who have undergone pulmonary
thromboendarterectomy in whom pulmonary hypertension persists, particularly
when the surgeon believes that clot removal has been successful.
References
-
Primack SL, Muller NL, Mayo JR, Remy-Jardin M, Remy J. Pulmonary
parenchymal abnormalities of vascular origin: high-resolution CT findings.
RadioGraphics
1994;14:739
-746[Abstract]
-
Worthy SA, Muller NL, Hartman TE, Swensen SJ, Padley SPG, Hansell
DM. Mosaic attenuation pattern on thin-section CT scans of the lung:
differentiation among infiltrative lung, airway and vascular diseases as a
cause. Radiology
1997;205:465
-470[Abstract/Free Full Text]
-
Sherrick AD, Swensen SJ, Hartman TE. Mosaic pattern of lung
attenuation on CT scans: frequency among patients with pulmonary artery
hypertension of different causes. AJR
1997;169:79
-82[Abstract/Free Full Text]
-
Rubens FD, Wells P, Bencze S, Bourke M. Surgical treatment of
chronic thromboembolic pulmonary hypertension. Can Respir
J 2000;7:49
-57[Medline]
-
Baker PB, Goodwin RA. Pulmonary artery sarcomas: a review and
report of a case. Arch Pathol Lab Med
1985;109:35
-39[Medline]
-
Smith WS, Lesar MS, Travis WD, et al. Case report: MR and CT
findings in pulmonary artery sarcoma. J Comput Assist
Tomogr 1989;13:906
-909[Medline]
-
Bressler EL, Nelson JM. Primary pulmonary artery sarcoma: diagnosis
with CT, MR imaging, and transthoracic needle biopsy.
AJR
1992;159:702
-704[Free Full Text]
-
Weinreb JC, Davis SD, Berkmen YM, et al. Pulmonary artery sarcoma:
evaluation using Gd-DTPA. J Comput Assist Tomogr
1990;14:647
-649[Medline]
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Introduction
Case Reports
