AJR 2004; 183:39-47
© American Roentgen Ray Society
MRI of Cystic and Soft-Tissue Masses of the Shoulder Joint
Erin E. O'Connor1,
Larry B. Dixon,
Terrance Peabody and
Gregory Scott Stacy
1 All authors: Department of Radiology, University of Chicago Hospitals, 5841 S
Maryland Ave., MC2026, Chicago, IL 60637.
Received October 15, 2003;
accepted after revision December 1, 2003.
Address correspondence to E. E. O'Connor
(eeoconnor{at}yahoo.com).
Introduction
The shoulder is commonly evaluated on MRI to confirm or exclude internal
derangement. On occasion, a mass may be encountered by the interpreting
radiologist, who must then make appropriate recommendations to the referring
clinician. In certain cases, referral to an orthopedic surgeon specializing in
neoplasms is appropriate. This pictorial essay reviews cystic and soft-tissue
lesions around the shoulder joint, focusing on those entities with relatively
specific MRI features.
Cysts
Paralabral cysts (Figs. 1
and 2A,
2B,
2C) typically arise adjacent to
a torn glenoid labrum. On MRI, they appear as well-defined, uni- or
multiloculated, nonenhancing, fluid-filled masses. The cysts may extend into
the suprascapular or spinoglenoid notches and compress the suprascapular
nerve. This compression can result in atrophy of the supraspinatus or
infraspinatus muscle or both. These cysts should be considered causes of
unexplained rotator cuff weakness in young patients, although they may also be
discovered incidentally on MRI.
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Fig. 2A. —37-year-old woman with paralabral cyst and associated labral
tear. T1-weighted coronal oblique image with fat saturation obtained after
intraarticular injection of gadolinium shows paralabral cyst (arrow)
in association with labral tear (arrowhead).
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Fig. 2B. —37-year-old woman with paralabral cyst and associated labral
tear. T2-weighted coronal oblique image with fat saturation obtained after
intraarticular injection of gadolinium shows location of paralabral cyst
(arrow) in suprascapular notch.
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Fig. 2C. —37-year-old woman with paralabral cyst and associated labral
tear. Proton density–weighted coronal oblique image shows how cyst
located in suprascapular notch can cause fatty atrophy of infraspinatus muscle
(INF) as shown by fat signal intensity in fibers of muscle. DEL = deltoid.
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Cysts may also arise in the rotator cuff musculature. At least one study
suggests an association between such cysts and rotator cuff tears
[1]
(Fig. 3).
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Fig. 3. —57-year-old woman with rotator cuff tear. T2-weighted coronal
oblique image shows how cysts can be associated with tears of rotator cuffs.
Bilobed fluid-signal-intensity mass (arrow) is present in
supraspinatus muscle (SUP). Note retraction of supraspinatus tendon with
full-thickness tear (arrowhead) at tendon insertion site.
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Acromioclavicular (AC) joint cysts (Fig.
4A,
4B) are fluid-filled masses
arising in the setting of a long-standing full-thickness rotator cuff tear.
Chronic friction from the high-riding humeral head leads to mechanical wear of
the articular capsule of the AC joint, allowing passage of fluid from the
glenohumeral joint into and often beyond the AC joint (referred to as the
geyser sign on arthrograms). The fluid can distend the AC joint capsule and
form a cystic mass above the joint, which can be uni- or multiloculated.
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Fig. 4A. —62-year-old man with chronic rotator cuff tear. Proton
density–weighted coronal oblique image shows unilocular mass of fluid
signal intensity (white arrowheads) between acromion process (A) and
distal clavicle (C) compared with acromioclavicular (AC) joint cyst (white
arrow), which has occurred in setting of long-standing full-thickness
rotator cuff tear. Black arrow indicates retracted supraspinatus tendon, and
black arrowheads show atrophic supraspinatus muscle.
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Fig. 4B. —62-year-old man with chronic rotator cuff tear. T2-weighted
sagittal oblique image with fat saturation shows multilocular AC joint cyst
(arrows). Weakened AC joint capsule allows passage of fluid (linear
high signal intensity [arrowheads] between acromion [A] and clavicle
[C]) with resultant distention of joint capsule and cyst formation (referred
to as geyser sign on MR arthrograms).
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Tumors of Fluid or Near Fluid Signal Intensity
Myxomas (Fig. 5A,
5B) are benign neoplasms that
are thought to arise from mucopolysaccharide-producing fibroblasts. The MRI
findings of an intramuscular mass with relatively low signal intensity on
T1-weighted images and markedly high signal intensity on T2-weighted images
reflect high water and mucin content and low collagen content. A recently
described characteristic feature on T1-weighted images is that of a rim of fat
signal intensity between the lesion and the surrounding muscle
[2].
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Fig. 5A. —51-year-old man with myxoma. T1-weighted axial image shows
well-circumscribed mass of low signal intensity in deltoid muscle that was
histologically proven to be myxoma. Recently described characteristic feature
[2] is presence of small rim of
fat signal intensity (arrowheads) between lesion and surrounding
muscle, very likely due to focal muscular atrophy resulting from extension of
mucoid material.
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Fig. 5B. —51-year-old man with myxoma. T2-weighted image shows that
myxoma has markedly high signal intensity (arrow), reflecting
histologic composition of high water and mucin content and low collagen
content.
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Nerve sheath tumors (Fig.
6A,
6B) consist of schwannomas and
neurofibromas, which in many cases cannot be distinguished on imaging. MRI
reveals low signal intensity on T1-weighted images, high signal intensity on
T2-weighted images, and avid contrast enhancement, features that are similar
to those of other neoplasms. However, a characteristic fusiform shape oriented
longitudinally along the nerve with tapered ends and the target sign, which
consists of high peripheral signal intensity surrounding central low signal
intensity on T2-weighted images, can suggest the diagnosis
[3].
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Fig. 6A. —35-year-old woman with neuroma. T1-weighted coronal image
shows that nerve sheath tumor is of low signal intensity (arrow) and
has characteristic fusiform shape with tapered ends contiguous with parent
nerve (arrowheads).
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Fig. 6B. —35-year-old woman with neuroma. T2-weighted axial image with
fat saturation shows MRI target sign, consisting of high peripheral signal
intensity (arrow) in conjunction with central region of low signal
intensity specific for nerve sheath tumor.
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Fat-Containing Masses
Lipoma (Fig. 7A,
7B) represents the most common
soft-tissue tumor of adulthood and the most common benign tumor affecting the
shoulder girdle, usually arising in the subcutaneous tissues but often in
muscle. On MR images, lipomas are generally nonenhancing homogeneous masses
with the same signal intensity as subcutaneous fat on all pulse sequences.
Thin septa may be present.
Although most liposarcomas are indistinguishable from other malignant
sarcomas on MRI, low-grade liposarcomas and atypical lipomas may possess
enough fat visible on MRI to suggest the diagnosis (Fig.
8A,
8B,
8C). Imaging features that
indicate such a lesion include large lesion size, thick septa or nodular
nonadipose areas, and enhancement after IV gadolinium administration
[4].
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Fig. 8A. —68-year-old man with liposarcoma. T1-weighted axial image
reveals mass (arrowheads) of predominantly fat signal intensity;
presence of area in mass that does not completely follow fat signal intensity
(arrow) suggests that this may be atypical lipoma or low-grade
liposarcoma.
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Fig. 8B. —68-year-old man with liposarcoma. On fat-suppressed
T2-weighted image, part of mass does not lose its signal intensity
(arrow) in contrast to homogeneous saturation seen in remainder of
lesion (arrowheads). This characteristic is consistent with atypical
lipoma or low-grade liposarcoma.
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Fig. 8C. —68-year-old man with liposarcoma. T1-weighted axial image
with fat saturation obtained after administration of gadolinium shows that
this same region (arrow) in fatty mass (arrowheads)
enhances; this feature is suggestive of malignancy.
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Elastofibroma dorsi (Fig.
9) is a benign soft-tissue lesion of the periscapular area with
fibrous and fatty components, most commonly seen in older women. The
pathogenesis is related to mechanical friction between the chest wall and the
scapula, and many patients have an occupational history of heavy manual labor.
The size varies from a few centimeters to as large as 20 cm. On MRI, the mass
is nonencapsulated and lenticular-shaped, with its long axis oriented
craniocaudally beneath the scapula. Areas of intermediate signal intensity on
T1-weighted images and low signal intensity on T2-weighted images are due to
dense fibrous tissue. Interspersed linear strands with signal intensity
similar to that of subcutaneous fat reflect the adipose tissue in the lesion
[5]. Variable enhancement has
been reported.
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Fig. 9. —73-year-old woman with elastofibroma. T1-weighted sagittal
image reveals nonencapsulated mass (arrow) with lenticular shape and
its long axis in craniocaudal orientation beneath scapula
(arrowheads). Areas of intermediate signal intensity are due to dense
fibrous tissue, whereas interspersed linear strands of fat signal intensity
reflect adipose tissue in lesion.
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Masses with Low Signal Intensity on T2-Weighted Images
Dense ossification or calcification can result in masses of low signal
intensity on T2-weighted images. Tumoral calcinosis
(Fig. 10) refers to masslike
soft-tissue deposition of calcium, typically around large joints. Primary
tumoral calcinosis is an uncommon disorder usually manifesting in the second
and third decades of life in black patients, with a family history noted in
30–40% of these patients. Secondary tumoral calcinosis is most commonly
seen in patients with chronic renal failure but is also seen in patients with
scleroderma and other systemic disorders.
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Fig. 10. —29-year-old woman with chronic renal failure who developed
tumoral calcinosis. T2-weighted axial image shows predominantly
low-signal-intensity calcified mass (arrowheads) in subdeltoid bursa
consistent with tumoral calcinosis.
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Areas of low signal intensity in a mass on all pulse sequences may
correspond to dense collagen, characteristic of fibrous tumors (Fig.
11A,
11B,
11C). Enhancement of such
tumors is seen after administration of gadolinium, particularly in regions
that are more cellular and contain less collagen
[6]. MRI can show the extent of
these aggressive lesions that tend to invade muscle, encase neurovascular
structures, and extend along fascial planes.
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Fig. 11B. —50-year-old woman with desmoid tumor. T2-weighted image shows
that most of mass (arrowheads) remains low in signal intensity,
characteristic of fibrous tumor (in this patient, desmoid tumor). Bands of low
signal intensity on both T1-weighted (A) and T2-weighted (B)
images correspond to areas of dense collagen; areas of high signal intensity
on T2-weighted image (B) correspond to hypercellular areas, and thus
high water content, in tumor.
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Hemosiderin deposition occurs after breakdown of extracellular
methemoglobin, weeks to months after the initial appearance of blood products
in soft tissue. Hemosiderin characteristically is of decreased signal on both
T1- and T2-weighted sequences. Hypervascular tumors that bleed repeatedly may
appear unusually dark on T2-weighted images because of their hemosiderin
content (Fig. 12A,
12B).
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Fig. 12B. —64-year-old man with renal cell carcinoma and metastasis to
trapezius muscle. T2-weighted image shows that mass (arrowheads)
remains low in signal intensity because of hemosiderin content from repeated
episodes of bleeding.
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Other Masses
Soft-tissue sarcomas (Fig.
13A,
13B,
13C) generally show low signal
intensity on T1-weighted images and high signal intensity on T2-weighted
images and enhance vividly after IV gadolinium administration. These tumors
are typically large and arise in the deep tissues (e.g., in muscle). Malignant
fibrous histiocytoma and liposarcoma are the most common malignant soft-tissue
tumors of the shoulder.
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Fig. 13B. —49-year-old woman with biopsy-proven malignant fibrous
histiocytoma. T2-weighted image shows that mass (arrowheads) has very
high signal intensity, largely due to tumor-associated edema.
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Fig. 13C. —49-year-old woman with biopsy-proven malignant fibrous
histiocytoma. T1-weighted fat-suppressed axial image obtained after
administration of gadolinium shows marked enhancement in mass
(arrowheads). These features are all typical of sarcoma, but no
specific features suggest its histology.
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The MRI appearance of hematoma depends on the age of the lesion. On
T1-weighted images, a subacute hematoma (Fig.
14A,
14B) shows increased signal
intensity because of extracellular methemoglobin. Fat-suppressed sequences are
useful for distinguishing blood from fat because the signal intensity of a
subacute hematoma remains bright whereas that of a fatty lesion decreases. A
hypointense rim may develop on T1- and T2-weighted images because of
hemosiderin deposition. If there is no trauma history or the mass does not
decrease in size over time, the possibility of a hemorrhagic neoplasm should
be considered [7].
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Fig. 14A. —58-year-old woman with subacute hematoma adjacent to lipoma.
T1-weighted axial image shows subacute hematoma (white arrow) with
relatively increased signal intensity due to extracellular hemoglobin. Compare
hematoma with higher signal intensity mass (black arrow), which is
lipoma.
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Fig. 14B. —58-year-old woman with subacute hematoma adjacent to lipoma.
T1-weighted fat-suppressed MR image shows that signal intensity of subacute
hematoma (white arrow) remains bright, whereas that of lipoma
(black arrow) "drops out."
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Vascular malformations (Fig.
15A,
15B) on MRI are typically
poorly marginated, heterogeneous masses that may consist of multiple
serpentine structures. Foci of signal void (representing high-flowing vascular
channels, phleboliths, or thrombi) may be interspersed with areas of increased
signal intensity (representing fatty septa). Avid enhancement is consistent
with their vascular nature [8].
The MRI appearance of hemangiomas and lymphangiomas can be similar, with the
former being much more common than the latter.
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Fig. 15A. —36-year-old man with hemangioma. On T1-weighted axial image,
black arrow indicates lesion with some low signal intensity peripherally and
interspersed areas of high signal intensity due to presence of fat.
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Fig. 15B. —36-year-old man with hemangioma. T1-weighted fat-suppressed
MR image shows that mass (arrow) markedly enhances after
administration of gadolinium. This characteristic is typical of
hemangioma.
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Introduction
Cysts
