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705

Case

Thoracic

Periaortic

Ella A. Kazerooni,1

Tumors unusual,

adjacent

David

Lymphoma

M. Williams,1

to the descending

and can mimic

aortic

disease,

and G. Michael

thoracic specifically

aorta

Mimicking

Aortic

Report

Dissection

Deeb2

are

aneurysm

or dissection, both clinically and radiologically. Isolated tumors have been reported to mimic aortic dissection or aneurysm on chest radiographs and angiograms, and a single case of oat cell carcinoma has been reported to mimic aortic dissection on CT scans. We present a case of limited periaortic thoracic non-Hodgkin’s lymphoma surrounding the lumen of the aorta and mimicking aortic dissection on CT, MR, angiography, and intravascular sonography.

there was no aortic wall thickening, irregularity, or tear to suggest intramural hematoma and aortic dissection. The diagnosis of neoplastic encasement was suggested; however, in view of the possibility

of aortic dissection

without

intimal tear [1], aortic dissection

could

not be excluded.

Dynamic axial CT was then repeated. Ten-millimeter-thick uous sections were imaged with a CT/T 9800 Advantage

contigscanner

(GE Medical Systems) after IV administration of 100 ml of 60% contrast medium (Hypaque 60, Winthrop Pharmaceuticals, New York, NY) at 2 mI/sec for 20 sec, then at 1 mI/sec with a power injector. CT revealed a rind of tissue, measuring 2-3 cm, encasing the mid

and distal portion of the descending thoracic aorta for a length of 10 cm and a small left-sided pleural effusion (Fig. 1 B). The soft-tissue mass

Case Report The patient is a 79-year-old asymptomatic man with a history of hypertension and mild peripheral vascular occlusive disease. At the time of routine physical examination, posteroanterior and lateral chest radiographs revealed a large left-sided pleural effusion and widening of the mediastinal contour on the left, initially thought to represent abnormal enlargement of the mid-distal portion of the descending thoracic aorta (Fig. 1A). A preliminary diagnosis of chronic aortic dissection or aortic aneurysm was made. A contrast-enhanced CT

scan of the chest obtained at the referring institution tissue surrounding the descending thoracic aorta.

revealed

soft

The patient was referred to our institution for angiography to further explore the diagnosis of aortic dissection. Thoracic aortography showed mild narrowing of the aortic lumen at the level of the abnormal penaortic tissue. The aortic wall was normal from the level of the left

subclavian artery origin to the diaphragmatic hiatus on intravascular sonography performed with a 6.2-French, 12.5-MHz transducer (Boston Scientific, Received 1

Watertown,

MA; Diasonics,

March 23, 1992; accepted

Department of Radiology,

Kazerooni. 2

AJR 159:705-707,

had not changed in size since the CT examination 4 weeks The soft tissue was external to faint aortic wall calcification and measured 47 H in attenuation. CT-guided aspiration of the periaortic tissue was done with the patient prone. Two passes were made with a 22-gauge needle yielding 5 ml of serosanguineous fluid and 5 ml of dark red blood. No neoplastic cells were found. earlier.

University

Milpitas,

CA). In particular,

after revision April 16, 1992.

of

Michigan

Hospitals,

Box

To further characterize the nature of the periaortic tissue, we did an MR examination with a 1 .5-T unit (Signa, GE Medical Systems, Milwaukee, WI). Coronal Ti -weighted (400/20 [TR/TE]), axial Ti weighted (750/30), axial spin-density and T2-weighted (2000/40, 80) spin-echo images were obtained. An axial gradient-echo sequence (33/15/30#{176})also was obtained. After IV administration of 10 ml gadopentetate dimeglumine (Magnevist, Berlex Imaging, Wayne, NJ) an additional axial Ti-weighted (750/30) sequence was obtained. -

The tissue was of intermediate signal intensity on both Ti - and T2weighted images and enhanced minimally with contrast administration (Figs. 1C and 10). The signal characteristics were not consistent with recent hematoma and suggested the possibility of fibrosis or an unusual neoplasm, such as malignant fibrous histiocytoma or lymphoma. Although the signal characteristics of the mass were con-

0030, 1500 E.

Medical

of Surgery, Section of Thoracic Surgery, University of Michigan Hospitals, October

1992 0361 -803X/92/1

594-0705

Center

Dr., Ann Arbor, MI 48109.

Address

reprint requests to E. A.

1500 E. Medical Center Dr., Ann Arbor, MI 48109.

© American Roentgen Ray Society

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706

KAZEROONI

ET

AL.

AJR:159,

October

1992

Fig. l.-79-year-old asymptomatic man with a history of hypertension and mild peripheral vascular occlusive disease. A, Chest radiograph shows widening of descending thoracic aortlc shadow (arrows) and left-sided pleural effusion. B, Contrast-enhanced CT scan shows circumferential periaortic soft tissue, with faint aortic wall calcification and a leftslded pleural effusion. C and D, Coronal TI.welghted (C) and axial Tl-weighted contrast-enhanced (D) MR Images show periaortic soft tissue of intermediate signal intensity and a left-sided pleural effusIon.

sistent with chronic hematoma, the stable size and attenuation of the mass during the 4-week period suggested that this was less likely. A second CT-guided aspiration was performed 4 days later. Six passes were made, including two passes each with 22-, 20-, and 18gauge needles. The specimens contained collagen and lymphoid cells. No tissue diagnosis could be made. A cytopathologist was present during both CT-guided procedures for preparation of the specimens

and consultation. At exploratory thoracotomy, gelatinous, dark, serous fluid was present in the left pleural space. The left lung was adherent to the aorta and firm, white-tan soft tissue encased the descending thoracic aorta. Two biopsy specimens were obtained. The fluid from the left lung contained 147,000 RBCs/mm3 (0.15 x 1012/I) and 1320 WBCs/ mm3 (1320 x 106/I). The leukocytes were 96% lymphocytes, which were mature at cytologic evaluation. Gram stain, aerobic and anaerobic cultures, fungal smear, and culture were all negative for infection. The biopsy specimens measured i .5 x 1.0 x 0.5 cm and 1.5 x 0.8 x 0.3 cm and yielded the diagnosis of diffuse, mixed, small cleavedcell and large-cell lymphoma with sclerosis. Staging evaluation, in-

cluding abdominal and pelvic CT, and bone marrow no other evidence of lymphoma. After chemotherapy

biopsy revealed the soft-tissue

mass completely

resolved.

Ten months

later, ro evidence

of recurrent

disease was present.

Discussion The diagnosis often

difficult.

diverse,

of both aortic The clinical

and radiographically

dissection

from

tumor.

dissection

appearance

Aortic

and lymphoma

of aortic

it may be difficult dissection

dissection

is is

to differentiate

can masquerade

as

another disease, including tumor; and other diseases may look like aortic dissection. Patients with aortic dissection may have signs and symptoms that mimic myocardial infarction, aortic

regurgitation,

hypertensive

crisis,

pericarditis,

cholecys-

titis, cerebrovascular accident, spinal cord ischemia, mesenteric infarction, superior vena cava syndrome, acute pulmonary disorders, or mediastinal neoplasm [2]. Conversely, in a series

of 176 patients

undergoing

angiography

for suspected

aortic dissection during a period of 20 years, 55 patients had normal angiographic findings. Although four of these angiographic findings were later proved to be false-negative, 51

LIMITED

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AJR:159, October1992

THORACIC

PERIAORTIC

patients (29%) had a different disease [2]. Several mediastinal tumors have been reported to masquerade as aortic dissection on radiographs [2-5]. Conversely, aortic dissection has been reported to mimic tumor [6]. This includes patients with signs and symptoms of acute aortic dissection, as well as asymptomatic patients with abnormal findings on chest radiographs. Most of these reports describe findings on plain films and/or thoracic aortograms. In the case in which aortic dissection

mimicked

a lung tumor

at aortography,

a large

mass

was seen displacing the aortic arch inferiorly without opacification of a false lumen [6]. At surgery, the dissection had leaked into the lung, which contained an 8 x 1 0 cm hematoma. Many vascular abnormalities, including aneurysms, tortuosity, and pseudocoarctation may radiographically simulate neoplasm.

Eight cases of tumor mimicking aortic dissection or aneurysm have been reported. Eagle et al. [2] describe three patients with chest pain and normal thoracic aortograms in whom lymphoma, hemorrhagic rupture of a mediastinal cyst, and metastatic undifferentiated carcinoma mimicked aortic dissection.

Cyst

rupture

or hemorrhage

into the tumor

was

thought to be the cause of sudden severe pain. Other tumors, including two cases of oat cell carcinoma [3, 5] and a single case of a parathyroid adenoma with hemorrhage [4], have been reported to mimic aortic dissection; single cases of malignant schwannoma and extramedullary plasmacytoma have been reported to mimic aortic aneurysm [2]. CT was performed in both cases of oat cell carcinoma. Shin et al. [5] describe a case of metastatic oat cell carcinoma mimicking aortic dissection and imaged with contrast-enhanced CT. The abnormal soft tissue abutted a portion of the aortic wall and did not surround the aortic lumen. Additionally, the extent of the abnormality was not contiguous, with a skip area of several centimeters between two regions of abnormal periaortic

tissue.

In the

second

case

of oat

cell

carcinoma,

abnormal paraaortic soft tissue was believed to represent a thrombosed lumen of aortic dissection, as no contrast material was seen adjacent to the aortic lumen [3]. Retroperitoneal lymphoma is not rare. Circumferential encasement

of the abdominal

aorta

is less common,

and often

nodular. Chnsholm et al. [7] report that 59 patients among 1 0,000 patients undergoing a body CT examination during a 4-year period at one hospital had circumferential paraaortic abdominal

masses.

Thirty-two

(54%)

of these

patients

had

lymphoma. The paraaortic mass had smooth margins in 22 cases (69%) and nodular in 10 cases (31 %) of lymphoma. Lymphoma may have many appearances, but in the chest it typically involves mediastinal and, to a lesser extent, hilar lymph nodes. Pulmonary parenchymal, pleural, pericardial, chest wall, and endobronchial forms are less common, seen more frequently with non-Hodgkin’s lymphoma than with Hodgkin’s lymphoma, and can mimic many benign and malignant diseases [8]. Although lymphoma encasing the abdominal aorta is common, and encasement of other structures such as the ureter has been reported, thoracic periaortic disease has not been described. The workup of this patient was lengthy and expensive, applying some of the most sophisticated imaging techniques. In reviewing the alternatives in the evaluation of this patient, intravascular sonography provided the most pivotal informa-

DISSECTION

707

tion in the evaluation of the periaortic mass, showing an intact aortic wall, without intimal defect or intramural hematoma. Although intravascular sonography is a promising new technique for the evaluation of vascular and perivascular disease, its sensitivity

vascular

is not yet known.

sonograms

verse intimal

The axial

raises the possibility

tear may be missed.

orientation

of intra-

that a small trans-

Consequently,

the diagnosis

of aortic dissection was not completely excluded. The diagnosis of aortic dissection may be difficult, both clinically and radiographically. CT and angiography may be unable to differentiate mural from extramural disease. The attenuation on CT scans and signal characteristics on MR images of the mass in this case could not be used to distinguish chronic intramural hematoma from a malignant tumor. Although aortic dissection has been reported in the absence of an intimal tear [1 ], the circumferential nature of the abnormal periaortic soft tissue on CT scans and MR images, together with the lack of change in size or attenuation of the mass on CT scans in a 4-week period suggested that this was not an aortic dissection. Although our pathologists can diagnose malignant lymphoma with an 18- or 20-gauge needle aspirate, this is not always possible. A core biopsy is preferred both for diagnosis and immunohistochemical classification. Given the proximity of the mass to the aorta, and the inability to distinguish mass from aortic lumen without immediate contrast enhancement of the aorta, the physicians who did the CT-guided aspiration did not feel comfortable performing a core biopsy. When considering the differential diagnosis of abnormal enlargement of the descending thoracic aorta on chest radiographs, either in a patient with acute/chronic pain or in an asymptomatic patient, the diagnosis of aortic aneurysm or dissection

must

be raised.

Unusual

morphology

on CT scans

and MR images, such as a skip area, as previously reported, or unusual circumferential encasement of the aorta, as in this case of lymphoma, should suggest a neoplasm. Additionally, the use of intravascular sonography as an adjunct to thoracic aortography should be considered in the evaluation of suspected aortic dissection when the CT or MR appearance is atypical. REFERENCES 1 . Yamada

T, Shimpei T, Junta H. AOrtiC dissection without intimal rupture: with MR imaging and CT. Radiology 1988;168:347-352 2. Eagle KA, Quertermous T, Kritzer GA, et al. Spectrum of conditions initially suggesting acute aortic dissection but with negative aortograms. Am J Cardiol 1986;57:322-326 diagnosis

3. Margolis

JA, Cohn

cell carcinoma

1087-1 088 4. Berry BE, Carpenter rhage

from

RA, Griffin JP, Flanagan WH, Person BY. Oat as a pseudoaneurysm. South Med J 1980;73:

presenting

parathyroid

PC, Fulton RE, Danielson GK. Mediastinal hemoradenoma simulating aortic dissection. Arch Surg

1974;108:740-741 5. Shin MS, Ho KJ, Kirklin JW, Sears masquerading as aortic dissection: for their distinction. J Comput Assist 6. Tandon AP, Lukacs LI, Cooke NJ,

NJ. Metastatic mediastinal neoplasm a skip sign on computed tomography Tomogr

I983;9:299-303

lonescu MI. Dissection of the aorta mimicking lung tumour. J Cardiovasc Surg 1980;21 :251 -252 7. Chrisholm RA, Coltart RS, Cooper P, Dixon AK. Circumferential para-aortic masses: computed tomographic observations. C/in Radiol 1986;37: 531 -535 8. Bragg DG, Colby TV, Ward JH. New concepts in the non-Hodgkin lymphomas: radiologic implications. Radiology 1986;159:289-304