AJR 2002; 178:93-96
© American Roentgen Ray Society
Symptomatic Dysrhythmia Caused By a Posterior Mediastinal Angiomyolipoma
Drew A. Torigian1,
Larry R. Kaiser2,
Lorinda A. Soma3,
John E. Tomaszewski3,
Robert Kotloff4 and
Evan S. Siegelman1
1
Department of Radiology, University of Pennsylvania Medical Center, 1st Fl.,
Founders Bldg., 3400 Spruce St., Philadelphia, PA 19104-4283.
2
Department of Surgery, University of Pennsylvania Medical Center,
Philadelphia, PA 19104.
3
Department of Pathology and Laboratory Medicine, University of Pennsylvania
Medical Center, Philadelphia, PA 19104.
4
Department of Medicine, University of Pennsylvania Medical Center,
Philadelphia, PA 19104.
Received April 16, 2001;
accepted after revision July 16, 2001.
Address correspondence to E. S. Siegelman.
Introduction
We report the clinical and imaging findings of a patient with
lymphangioleiomyomatosis who presented with intermittent palpitations and
dysrhythmias caused by cardiac and pulmonary venous compression by a posterior
mediastinal angiomyolipoma.
Case Report
A 35-year-old woman with lymphangioleiomyomatosis presented with signs and
symptoms of intermittent palpitations and tachycardia. The patient's medical
history included recurrent bilateral pneumothoraces 9 years ago that were
treated with pleurodeses and acute abdominal pain and anemia 8 years ago that
were treated with surgery. At the time of the surgery, a hemorrhagic right
renal angiomyolipoma was removed, and resected regional retroaortic and
retrocaval lymph nodes were also involved by angiomyolipoma.
MR imaging of the chest and upper abdomen at this time showed a large (6.8
x 10.0 x 14.5 cm) smoothly marginated posterior mediastinal mass
of predominantly fat signal intensity with internal septations (Fig.
1A,1B,1C,1D).
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Fig. 1A. —35-year-old woman with history of lymphangioleiomyomatosis
and prior resection of right renal—retroperitoneal angiomyolipoma
presented with intermittent palpitations and tachycardia. Axial proton
density—weighted fast spin-echo image (TR/effective TE, 3529/18) at
level of left atrium shows posterior mediastinal mass (M) that mildly
compresses left atrium (A) and pulmonary veins (arrow), mildly
displaces heart anteriorly, and partially encases descending thoracic aorta
(asterisk).
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Fig. 1B. —35-year-old woman with history of lymphangioleiomyomatosis
and prior resection of right renal—retroperitoneal angiomyolipoma
presented with intermittent palpitations and tachycardia. Axial T1-weighted
conventional spin-echo image (TR/TE, 577/14) at level of aortic hiatus shows
that mass (M) extends from periceliac location in retroperitoneum posteriorly
through diaphragmatic crura (large arrow) into retrocrural space and
posterior mediastinum (small arrow). Mass is predominantly high in
signal intensity but is hypointense relative to subcutaneous fat and
retroperitoneal fat (F) with scattered low-signal-intensity internal
septations.
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Fig. 1C. —35-year-old woman with history of lymphangioleiomyomatosis
and prior resection of right renal—retroperitoneal angiomyolipoma
presented with intermittent palpitations and tachycardia. Coronal T1-weighted
conventional spin-echo images (577/15) show retroperitoneal (R) and posterior
mediastinal (M) components of mass separated by diaphragmatic crus (black
arrow). Mass extends superiorly to level of carina (C). Susceptibility
artifact (white arrow) is seen from prior right nephrectomy.
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Fig. 1D. —35-year-old woman with history of lymphangioleiomyomatosis
and prior resection of right renal—retroperitoneal angiomyolipoma
presented with intermittent palpitations and tachycardia. Coronal T1-weighted
conventional spin-echo images (577/15) show retroperitoneal (R) and posterior
mediastinal (M) components of mass separated by diaphragmatic crus (black
arrow). Mass extends superiorly to level of carina (C). Susceptibility
artifact (white arrow) is seen from prior right nephrectomy.
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It was decided to surgically remove the posterior mediastinal mass to
potentially alleviate the patient's palpitations and to prevent potentially
life-threatening sequelae of progressive cardiovascular compression. At
thoracotomy, a noninvasive fatty tumor was removed from the posterior
mediastinum. The mass was continuous with, but did not invade, the heart or
pulmonary veins. The patient's palpitations and dysrhythmias have not recurred
in the 10 months since surgery.
On pathologic examination, the gross specimen had an appearance consistent
with an angiomyolipoma (Fig.
2A). Histologic examination showed a predominance of mature
adipocytes with some spindle cells and vessels
(Fig. 2B), all of which
exhibited minimal pleomorphism. Immunohistochemical staining showed positivity
in the spindle cell population for HHF-35 (a smooth-muscle actin marker;
Fig. 2C), SMA (a smooth-muscle
actin marker), and HMB-45 (a marker for melanocytic lesions and for the
smooth-muscle component of lymphangioleiomyomatosis and angiomyolipoma;
Fig. 2D [1,
2]). In addition, the spindle
cells were negative for CD31 (an endothelial marker) and antibodies to
pancytokeratin. These findings confirmed the morphologic impression of muscle
differentiation of the spindle cells. Although the vasculature did not display
marked thickening of the media, the combined morphologic features in
association with the immunohistochemical phenotype were diagnostic of a
posterior mediastinal angiomyolipoma.
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Fig. 2A. —Gross and histopathologic findings of excised fatty posterior
mediastinal mass in 35-year-old woman. Photograph of sectioned gross specimen
appears as oval well-circumscribed fatty mass (M) with homogenous shiny
golden-yellow interior.
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Fig. 2B. —Gross and histopathologic findings of excised fatty posterior
mediastinal mass in 35-year-old woman. Photomicrograph of histologic specimen
shows mature adipocytes (A), plump spindle cells (arrow), and vessels
(V). (H and E, x10)
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Fig. 2C. —Gross and histopathologic findings of excised fatty posterior
mediastinal mass in 35-year-old woman. Photomicrographs of histologic
specimens with immunohistochemical staining show positivity of spindle cells
for smooth-muscle markers (arrows), confirming muscle
differentiation. These findings are diagnostic of posterior mediastinal
angiomyolipoma. (HHF-35 stain, [muscle common actin] x40 [C] and
HMB-45, [human melanoma, black-45] x40 [D])
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Fig. 2D. —Gross and histopathologic findings of excised fatty posterior
mediastinal mass in 35-year-old woman. Photomicrographs of histologic
specimens with immunohistochemical staining show positivity of spindle cells
for smooth-muscle markers (arrows), confirming muscle
differentiation. These findings are diagnostic of posterior mediastinal
angiomyolipoma. (HHF-35 stain, [muscle common actin] x40 [C] and
HMB-45, [human melanoma, black-45] x40 [D])
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Discussion
Angiomyolipoma is a choristoma (a lesion composed of ectopic rests of
normal tissue in abnormal arrangement) composed of fat, abnormal blood
vessels, and smooth muscle in varying relative proportions found most commonly
in the kidneys. It is the most common benign renal tumor, accounting for 0.3%
of renal masses. Approximately 90% of renal angiomyolipomas occur
sporadically, are typically solitary and unilateral, and occur more often in
middle-age women [1,
3]. The remainder of renal
angiomyolipomas occurs in tuberous sclerosis and less frequently in
lymphangioleiomyomatosis [3].
In tuberous sclerosis, renal angiomyolipomas occur in about 80% of patients,
are typically multiple and bilateral, and are found in young adults with an
equal sex distribution. In lymphangioleiomyomatosis, a forme fruste of
tuberous sclerosis, renal angiomyolipomas occur in 57% of patients and tend to
be solitary and unilateral, as in the presented patient
[1,
2].
Although renal angiomyolipomas are considered to be benign, some tumors
exhibit malignant features, including invasion of the renal vasculature and
perirenal structures, regional nodal involvement, local recurrence after
resection, and multicentric involvement of retroperitoneal lymph nodes or
organs not contiguous with the kidney. Multicentricity of the angiomyolipoma
is thought to be caused by either the congenital presence of cell precursors
in multiple sites or a form of benign metastases similar to that in benign
metastasizing leiomyoma [4].
Extrarenal angiomyolipomas are rare and are considered a reflection of
multicentricity rather than of true metastasis
[1,
4].
To our knowledge, this is the first report of an angiomyolipoma of the
posterior mediastinum that most likely grew by direct extension from the
retroperitoneum. We hypothesize that the posterior mediastinal angiomyolipoma
in this case was due to recurrence of an incompletely resected renal and
retroperitoneal angiomyolipoma with posterior and superior extension into the
posterior mediastinum through the diaphragm.
In the presented case, the posterior mediastinal mass predominantly
followed the imaging characteristics of fat on MR imaging, and the
differential diagnosis included an atypical lipoma, a well-differentiated
liposarcoma, a mature teratoma, and an angiomyolipoma. Well-differentiated
liposarcomas tend to have a more heterogeneous appearance than a lipoma and
may be indistinguishable from an atypical lipoma. A mature teratoma may appear
as a multilocular cystic mass with calcific, fluid, soft-tissue, or fat
components. The angiomyolipoma may not appear considerably different from the
other fatty masses, but the key to this diagnosis, as in the presented case,
is having an awareness of the patient's history of a prior renal or
retroperitoneal angiomyolipoma.
To our knowledge, the case presented is also the first of an angiomyolipoma
that caused cardiac dysrhythmias
[5]. There have been other
reports of mediastinal masses, such as pancreatic pseudocyst, bronchogenic
cyst, and lipoma, causing mass effect on the heart and great vessels and
leading to palpitations and dysrhythmias
[5,6,7].
The cause of the patient's dysrhythmia may also be due to external compression
of neural structures in the mediastinum or to mechanical stretching or
compression of the pulmonary veins that are known to be potential sources of
dysrhythmogenic foci [6,
8].
In summary, we present the MR imaging and pathologic findings of a patient
with lymphangioleiomyomatosis and a history of renal angiomyolipoma who
presented with intermittent palpitations and dysrhythmias caused by cardiac
compression by a posterior mediastinal angiomyolipoma.
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Introduction
Case Report
