Superficial Soft-Tissue Masses

Superficial Soft-Tissue
Masses: Analysis, Diagnosis,
and Differential
Considerations1
Francesca D. Beaman, MD2 ● Mark J. Kransdorf, MD ● Tricia R.
Andrews, MD ● Mark D. Murphey, MD ● Lynn K. Arcara, MD ● James
H. Keeling, MD
A wide variety of superficial soft-tissue masses may be seen in clinical
practice, but a systematic approach can help achieve a definitive diagnosis
or limit a differential diagnosis. Superficial soft-tissue masses can
generally be categorized as mesenchymal tumors, skin appendage lesions,
metastatic tumors, other tumors and tumorlike lesions, or inflammatory
lesions. With regard to their imaging features, these masses
may be further divided into lesions that arise in association with the
epidermis or dermis (cutaneous lesions), lesions that arise within the
substance of the subcutaneous adipose tissue, or lesions that arise in
intimate association with the fascia overlying the muscle. The differential
diagnosis may be limited further by considering the age of the patient,
anatomic location of the lesion, salient imaging features, and
clinical manifestations.
Introduction
Superficial soft-tissue masses are common in clinical practice, and the expanding
availability of radiologic imaging has increased radiologists’ familiarity with these entities.
In the case of some masses, such as superficial lipomas, the imaging characteristics
usually enable a definitive diagnosis. However, the imaging features of many
other superficial soft-tissue lesions may be disappointingly nonspecific, and the possible
diagnostic considerations initially may seem extensive. In such cases, the use of
a systematic approach can help narrow the differential diagnosis.
Superficial soft-tissue masses may be classified in one of the following general diagnostic
categories: mesenchymal tumors, skin appendage lesions, metastatic tumors,
Abbreviation: SE _ spin echo
RadioGraphics 2007; 27:509–523 ● Published online 10.1148/rg.272065082 ● Content Codes:
1From the Departments of Radiology (F.D.B., M.J.K.) and Dermatology (T.R.A., J.H.K.), Mayo Clinic, 4500 San Pablo Road, Jacksonville, FL
32224-3899; and Department of Radiologic Pathology, Armed Forces Institute of Pathology, Walter Reed Army Medical Center, Washington, DC
(M.J.K., M.D.M., L.K.A.). Recipient of a Certificate of Merit award for an education exhibit at the 2005 RSNA Annual Meeting. Received April 26,
2006; revision requested June 12 and received July 26; accepted July 31. All authors have no financial relationships to disclose. Address correspondence
to M.J.K. (e-mail: kransdorf.mark@mayo.edu).
2Current address: Department of Radiology, Washington Hospital Center, Washington, DC.
The opinions or assertions contained herein are the private views of the authors and are not to be construed as official nor as reflecting the views of the
Department of the Army or the Department of Defense.
See last page
TEACHING
POINTS
other tumors and tumorlike lesions, and inflammatory
lesions. Although these categories comprise
a plethora of possible diagnoses, an orderly
list of differential considerations may be constructed
by considering the patient’s age, the anatomic
site of the mass, and the specific location of
the mass within the superficial tissue.
For purposes of analysis, it is most useful to
consider two patient age groups: (a) adults and
(b) children and adolescents. The dividing line
between these groups is not rigidly defined, but
we have arbitrarily designated those in the first 2
decades of life as children and adolescents. Anatomic
location is also best considered in general
categories such as the extremity, trunk, or head
and neck. However, certain lesions show a striking
predilection for a more specific anatomic location,
as is true of epithelioid sarcoma, which usually
occurs in the hand and wrist. Epithelioid sarcoma
is rare, accounting for just over 1% of all
sarcomas, but more than 40% of epithelioid sarcomas
occur in the hand and wrist. Finally, the
location of a lesion within the superficial tissue is
best described as cutaneous (epidermis and dermis);
subcutaneous (eg, adipose tissue); or fascial,
overlying the muscle or deep tissue (Fig 1). After
a differential diagnosis is established on the basis
of the patient’s age and the location of the lesion
(anatomic site and specific location within the
superficial tissue), it may be further limited and
ordered, or a specific diagnosis may be made, by
considering that information in combination with
the imaging characteristics.
The article is based on our experience with
superficial soft-tissue masses. It is not intended as
a comprehensive review but, rather, as an overview,
with emphases on lesions that are more
common or relatively more common and on diagnoses
that may be suggested by MR imaging features.
Mesenchymal Tumors
The category of mesenchymal tumors is described
in Table 1. The most common mesenchymal superficial
malignancy is dermatofibrosarcoma protuberans,
which arises from the dermis and therefore
is considered a cutaneous lesion. Dermatofibrosarcoma
protuberans accounts for about 6%
of all soft-tissue sarcomas. The lesions usually
are manifested at MR imaging as unmineralized
nodular masses with nonspecific signal intensity
and moderate enhancement (Fig 2) (1). Other
benign and malignant mesenchymal tumors may
arise in association with the cutaneous tissue, but
Figure 1. Diagram shows the superficial soft-tissue layers.
510 March-April 2007 RG f Volume 27 ● Number 2
Figure 2. Exophytic dermatofibrosarcoma protuberans in the lower thigh of a 45-year-old man.
(a) Axial unenhanced CT image shows a large mass with ulceration at the skin surface (arrowheads).
(b) Axial short inversion time inversion recovery (4000/20/150) MR image shows extension
of the protuberant mass along the skin layers and into the cutaneous and subcutaneous fat.
(c) Photograph of a gross specimen cross section shows the mass with linear extension along the
skin layers (arrows), features identical to those seen at imaging. Scale is in centimeters.
Table 1
Mesenchymal Tumors
Diagnosis Classification Patient Age Comments
Dermatofibrosarcoma
protuberans
Cutaneous Adults (peak,
20–40 years)
Protuberant mass with skin involvement; a fascial
tail may be seen at imaging
Lipoma Subcutaneous Adults Signal intensity mirrors that of fat
Angiomas (hemangioma,
lymphangioma,
mixed)
Subcutaneous All ages Signal intensity is intermediate to high on images
obtained with fluid-sensitive MR pulse sequences
Peripheral nerve sheath
tumor (schwannoma,
neurofibroma)
Cutaneous,
subcutaneous
Adults Neurofibroma is usually associated with NF1;
malignant peripheral nerve sheath tumor is
rare
Malignant fibrous histiocytoma
Subcutaneous Adults Most common soft-tissue sarcoma, usually deep;
7%–10% of lesions are subcutaneous
Liposarcoma Cutaneous
(rare), subcutaneous
Adults Extremities, retroperitoneum; most lesions contain
some amount of fat
Leiomyosarcoma Subcutaneous Adults Nonspecific vascular mass; may be associated
with superficial veins
Epithelioid sarcoma Subcutaneous Adults (peak,
20–40 years)
Occurs on fingers, hands, forearms; imaging features
are nonspecific
Nodular fasciitis Fascial Adults (peak,
20–40 years)
Fascial tail may be seen at imaging
Fibromatosis Fascial Adults Signal intensity is low to intermediate
RG f Volume 27 ● Number 2 Beaman et al 511
their occurrence is unusual. Although the MR
imaging signal intensity of dermatofibrosarcoma
protuberans typically is nonspecific, areas of hemorrhage
may be seen within the tumor. In our experience,
linear extension along the skin surface
also may be seen and is suggestive of the diagnosis
(Fig 2b).
Most mesenchymal masses arise within the
subcutaneous adipose tissue. Lipomas are by far
the most frequently encountered subcutaneous
masses. Eighty percent of lipomas occur in adults,
and they are easily diagnosed on the basis of MR
imaging findings, including a signal intensity that
is characteristic of fat on MR images acquired
with any pulse sequence, as well as a lack of enhancement
after the administration of intravenous
contrast material (Fig 3).
Angiomatous lesions also are common. Hemangiomas
are the most common type of angiomatous
lesions, but mixed hemangiolymphangiomas
and pure lymphangiomas also may be seen. These
lesions produce a wide spectrum of clinical manifestations
and may occur in patients of all ages.
Classic large-vessel (cavernous) hemangiomas
have the generally characteristic imaging appearance
of infiltrative lesions in which serpentine vessels
interdigitate with fibroadipose tissue. Smallvessel
hemangiomas may have a more nonspecific
appearance, and the diagnosis may be suggested
more by their clinical manifestations (Fig 4).
Peripheral nerve sheath tumors are another
common type of mesenchymal tumor. Typically,
an entering and exiting nerve cannot be identified
in superficial lesions; however, the typical fusiform
shape, signal intensity, and enhancement
pattern often are present. Classic peripheral nerve
sheath tumors have a signal that is isointense to
that of skeletal muscle on T1-weighted MR images
and hyperintense to that of skeletal muscle
on T2-weighted images, with variable degrees of
inhomogeneity and enhancement (Fig 5) (2).
The most common subcutaneous malignant
soft-tissue tumor is the superficial variant of malignant
fibrous histiocytoma. Malignant fibrous
histiocytoma is the most common mesenchymal
malignancy and accounts for approximately 24%
of all soft-tissue sarcomas (3), with about 7%–
10% of occurrences being confined to the subcutis,
and there is typically no fascial involvement
(4,5). The superficial form of malignant fibrous
histiocytoma is histologically identical to the pleomorphic
form; however, as a result of its superficial
location, it has a benign clinical course.
Therefore, to distinguish it more clearly from the
deep, more biologically aggressive forms, superficial
malignant fibrous histiocytoma has been
termed atypical fibroxanthoma (6). Hemorrhage
is not uncommon in such lesions and is usually
well depicted on MR images.
Other superficial sarcomatous lesions include
liposarcoma, leiomyosarcoma, and epithelioid
sarcoma. Liposarcoma is the second most common
soft-tissue sarcoma, accounting for 16%–
18% of all malignant soft-tissue tumors. The lesions
usually are located in the extremities, particularly
the thigh, and in the retroperitoneum in
adults 40–59 years old. Superficial liposarcoma is
relatively uncommon, but when a superficial fatty
lesion does not meet the imaging criteria for the
diagnosis of lipoma, a lipoma variant should be
considered as a diagnostic possibility, as should
liposarcoma. The appearance of liposarcoma at
CT and MR imaging typically correlates with the
degree of tumor differentiation; tumors that are
more differentiated contain more fat and less soft
tissue (3).
Leiomyosarcoma accounts for about 5%–10%
of soft-tissue sarcomas (6). The lesions are highly
vascular, occur most often in mature adults, and
have a propensity to recur and metastasize. They
are often intimately associated with vessels. At
ultrasonography (US), they appear as circumscribed
echogenic masses, with marked internal
vascularity seen on Doppler US images. MR imaging
features usually are not specific (Fig 6).
Figure 3. Superficial (subcutaneous) lipoma
in a 51-year-old man with a large posterior
neck mass. Sagittal T1-weighted (620/17)
spin-echo (SE) MR image shows a well-marginated
lipomatous mass (*) in the subcutaneous
fat. The signal intensity of the lesion on all
MR images was identical to that of fat.
512 March-April 2007 RG f Volume 27 ● Number 2
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Point
Figure 4. Juvenile capillary hemangioma (strawberry nevus) in a 2-month-old girl.
(a) Axial unenhanced CT image shows infiltration of the skin and orbit (arrow). (b) Axial
T2-weighted (2000/80) SE MR image depicts a mass (*) that has infiltrated the subcutaneous
and deeper soft tissues. The signal intensity of the lesion at T2-weighted imaging was
nonspecific.
Figure 5. Multifocal
cutaneous neurofibromas
in a 78-
year-old man with
type 1 neurofibromatosis.
(a) Axial CT
image of the abdomen,
obtained with
oral and intravenous
contrast material,
shows multifocal
isoattenuating softtissue
masses (arrowheads)
indicative
of neurofibromas.
(b, c) Sagittal T2-
weighted turbo SE
(4000/102) MR image
(b) and sagittal
gadolinium-enhanced
fat-suppressed
T1-weighted
SE (650/16) MR image
(c) show hyperintense
signal in the
enhanced cutaneous
masses (arrows).
RG f Volume 27 ● Number 2 Beaman et al 513
Figure 6. Leiomyosarcoma arising from the
saphenous vein in a 53-year-old man. (a) Doppler
US image shows a circumscribed echogenic
mass with marked hypervascularity.
(b, c) Axial T1-weighted (802/17) (a) and
axial T2-weighted (2350/80) (b) SE MR images
show a circumscribed soft-tissue mass
(arrow) in the subcutaneous adipose tissue.
The signal intensity of the mass is indicative
of a solid lesion. (d) Axial gadolinium-enhanced
T1-weighted (675/17) fat-suppressed
SE MR image shows homogeneous moderate
enhancement of the mass (arrow). (e) Photograph
of the gross specimen shows a lobulated
mass that surrounds the saphenous vein (arrow).
Scale is in centimeters.
514 March-April 2007 RG f Volume 27 ● Number 2
Epithelioid sarcoma, conversely, is a rare sarcoma
that is seen predominantly in male adolescents
and young adults (ages 10–35 years). It is
manifested as a firm, solid single nodule or multiple
nodules that most commonly are located on
the forearms, hands, or fingers (6). Although epithelioid
sarcoma comprises only approximately
1%–2% of all soft-tissue sarcomas, it represents
21%–29% of all malignant lesions of the hand
and wrist in patients between the ages of 16 and
35 years. At radiography, epithelioid sarcoma
may appear as a soft-tissue mass with occasional
speckled calcification, cortical thinning, and osseous
erosion (6).
It is especially noteworthy that a superficial
lesion that extends through the fascia is more
likely to be a malignancy (Fig 7) (7).
Nodular fasciitis and fibromatosis are two entities
that may arise in the fascial layer. Nodular
fasciitis is a pseudosarcomatous benign fibrous
tumor that is thought to be reactive in etiology
and, therefore, to be self-limiting. It is primarily
located in the upper extremities in young adults
(ages 20–40 years) (6). At MR imaging, nodular
fasciitis demonstrates a nonspecific signal intensity.
After the administration of contrast material,
there is usually diffuse enhancement. An important
diagnostic feature at MR imaging is the linear
extension of the lesion along the fascia (fascial tail
sign), which also may appear enhanced (Fig 8).
Fibromatosis is a locally aggressive benign tumor
Figure 7. Superficial malignant fibrous histiocytoma in the upper thigh of a 78-year-old man. (a) Coronal
T1-weighted (700/13) SE MR image shows a large hypointense mass (arrows) that has arisen in the
subcutaneous tissue and has invaded and penetrated the tensor fascia lata. (b) Axial T2-weighted (2540/
80) SE MR image shows heterogeneously hypointense signal in the mass, as well as abnormal thickening
of the tensor fascia lata (arrow).
Figure 8. Nodular
fasciitis in the upper arm
of a 16-year-old boy.
Coronal T1-weighted
(600/20) (a) and coronal
T2-weighted (2000/
80) (b) SE MR images
of the shoulder show a
well-defined mass superficial
to the deltoid
muscle with a small linear
area of extension in
the proximal fascia (arrow
in b).
RG f Volume 27 ● Number 2 Beaman et al 515
Teaching
Point
that typically is seen in adults and that has low to
intermediate signal intensity on MR images
(Fig 9).
Skin Appendage Lesions
Skin appendage lesions originate in the epidermis
and dermis (Table 2). They are typically subcategorized
as proliferations of follicular lineage or
eccrine-apocrine differentiation. The lesions are
typically small and, consequently, are diagnosed
clinically. Imaging features are not usually specific,
and imaging is reserved for unusually large
or atypical lesions; however, such lesions often are
incidental findings at imaging.
The most common of these is probably the
infundibular cyst, or epidermal cyst. This simple
epithelial cyst is lined with infundibular or epidermal-
like cells that keratinize (8). The term sebaceous
cyst is a misnomer and should be avoided,
because these cysts are not of sebaceous differentiation
and their imaging characteristics vary according
to their internal contents. Large lesions
may contain dependent debris. Most frequently,
lesions are small and unilocular; however, large
multiloculated lesions may be manifested with a
rim of peripheral enhancement (9). At US, the
cyst appears as a circumscribed circular or oval
hypoechoic mass, often in association with a hair
follicle. The lesion has attenuation that is similar
to that of skeletal muscle on CT images and MR
signal that is isointense or slightly hypointense
compared with the signal in skeletal muscle on
T1-weighted MR images and hyperintense compared
with that on T2-weighted MR images (Fig
Figure 9. Musculoskeletal fibromatosis in the paraspinal region in a 20-year-old man. (a) Axial T1-weighted (800/
20) SE MR image shows markedly decreased signal intensity within a well-defined mass (arrows), a finding indicative
of a densely collagenous hypocellular lesion. The mass extends across the midline (arrowheads). T2-weighted images
(not shown) also showed decreased signal intensity in the mass. (b) Corresponding contrast-enhanced CT image
shows enhancement of the lesion and small fascial “tails” (arrowheads).
Table 2
Skin Appendage Lesions
Diagnosis Classification Patient Age Comments
Epidermal inclusion
cyst
Cutaneous (dermal) Adults Most common dermal cyst, often an
incidental finding at imaging
Pilomatricoma Cutaneous (dermal) Bimodal: children and
adults
Benign calcifying tumor
Cystadenoma Cutaneous (dermal) Adults Cystic ectasia of the dermal portion
of the eccrine duct
Cylindroma Cutaneous (dermal) Adults, mostly women Occurs on head, neck, and scalp
Syringoma Cutaneous (dermal) Adults Occurs on eyelids and upper cheeks
516 March-April 2007 RG f Volume 27 ● Number 2
Teaching
Point
10). No appreciable enhancement of the lesion
should be seen.
Pilomatricoma is a benign calcifying tumor
that is thought to arise from skin appendages
(10). The lesion arises in the dermis from primitive
cells that normally differentiate into hair matrix
cells (11,12). Although pilomatricoma accounts
for less than 1% of skin tumors, it is the
most common solid cutaneous tumor in patients
20 years of age and younger (13), with a secondary
peak occurrence among mature adults (ages
50–65 years). Tumors are small (usually less than
3 cm in diameter), grow slowly, are confined to
the subcutaneous tissue (10,11), and are seen
most commonly on the face, neck, and arms. Calcification,
which is more typically central, is seen
in about 85% of lesions (Fig 11).
Large lesions that arise in association with eccrine
(sweat) glands also may be manifested as
soft-tissue masses. Eccrine cystadenoma (eccrine
hidrocystoma) arises because of cystic ectasia of
the dermal portion of the eccrine duct, which results
in retention of secretions within simple cysts.
A large lesion of this type may be manifested as a
lobulated cystic mass. Contrast-enhanced MR
imaging has been reported to show enhancement
of the cyst wall with occasional small enhancing
papillary areas that projected into the lumen (14).
Cylindroma and syringoma are dermal tumors
of apocrine differentiation. They are characterized
by their clinical appearance and are not likely
to be encountered by a musculoskeletal specialist.
Cylindromas are seen primarily on the head,
neck, and scalp in women (Fig 12). Syringomas
are also predominantly found on the head in
adults, specifically on the eyelids and upper
cheeks.
Figure 10. Infundibular cysts at MR imaging and US. (a, b) Axial T1-weighted (600/20) (a)
and axial T2-weighted (2500/80) (b) SE MR images of the knee of a 45-year-old man with a history
of a mass for approximately 30 years show a well-defined but nonspecific mass (*) in the subcutaneous
adipose tissue. The lesion contents appear heterogeneous on the T2-weighted image,
with debris in the dependent aspect. (c) US image in a different patient shows an infundibular cyst
located in the skin (arrow) and two hairs (arrowheads) emerging from the cyst.
Figure 11. Pilomatricoma in the neck of a 7-year-old
boy. Axial contrast-enhanced CT image obtained with
bone window settings shows a mineralized mass (arrow)
with delicate ossification that is more prominent
peripherally.
RG f Volume 27 ● Number 2 Beaman et al 517
Metastatic Tumors
Soft tissue is relatively resistant to metastasis; although
soft tissue accounts for about 40% of total
body weight, soft-tissue metastases are very rare.
However, any malignancy may disseminate to the
skin, and 5%–10% of all cancer patients develop
skin metastases (Table 3). At clinical examination,
numerous small, hard or rubbery nodules
are found, typically on the chest, abdomen, or
scalp of an adult older than 40 years. Skin involvement
typically occurs near the site of the primary
tumor. Because of overall disease prevalence,
breast cancer is the most common primary
lesion that metastasizes to the skin in women
(15). In men, skin metastases from malignant
melanoma are most common, followed by those
from lung cancer (15). Cutaneous metastases are
frequently identified in clinical practice, but they
are uncommonly subjected to radiologic imaging.
Metastatic melanoma may be manifested with
a similar pattern of multiple subcutaneous nodu-
Figure 12. Multiple facial cylindromas in a 79-year-old woman. (a) Clinical photograph
of the patient’s ear shows numerous soft-tissue masses. (b) Axial unenhanced CT image
shows multiple isoattenuating cutaneous masses that involve both ears.
Table 3
Metastatic Tumors
Diagnosis Classification Patient Age Comments
Carcinoma Cutaneous Adults 5%–10% of all cancers; most common on the
chest, abdomen, and scalp
Melanoma Subcutaneous Adults Seen in 30% of patients with metastatic melanoma;
internal hemorrhage not uncommon
Myeloma Cutaneous, subcutaneous Adults Soft tissue is a frequent site of extraosseous
involvement
Table 4
Other Tumors and Tumorlike Lesions
Diagnosis Classification Patient Age Comments
Myxoma Cutaneous, subcutaneous Adults Characterized by fluidlike signal intensity,
variable enhancement
Lymphoma Cutaneous, subcutaneous Adults Primary soft-tissue lymphoma is rare
Granuloma
annulare
Cutaneous, subcutaneous Adults (cutaneous);
children, adolescents
(subcutaneous)
Subcutaneous form may be manifested
as a soft-tissue mass; decreased signal
intensity at MR imaging
518 March-April 2007 RG f Volume 27 ● Number 2
lar lesions, and its presence must be considered in
a patient who presents with multiple subcutaneous
nodules (16).
Teaching
Point
Such nodules are seen in more
than 30% of patients with metastatic melanoma,
usually in those with Clark level IV or V disease
(tumor invasion of the deep dermis or subcutaneous
fat), and they may be the only radiologic
manifestation of metastatic disease (Fig 13) (16).
Extraosseous manifestations of multiple myeloma
are found in less than 5% of patients and
are associated with more aggressive disease (17).
In patients with extraosseous disease, the typical
manifestation is a cutaneous or subcutaneous
nodule or nodules (17).
Other Tumors
and Tumorlike Lesions
Myxoma is a benign lesion characterized by an
abundant myxoid matrix and a paucity of spindleshaped
stromal cells. Perceived as rare, these lesions
are more common in surgical series and represent
approximately 3% of all benign tumors
subjected to biopsy. According to a report from
the Armed Forces Institute of Pathology about
approximately 200 myxomas of various anatomic
sites, 15% of the lesions arose in the cutaneous
tissue and 22% in the subcutaneous and aponeurotic
tissues (3,18,19). Myxoma typically shows a
homogeneous fluidlike signal intensity (Fig 14,
Table 4). At contrast-enhanced imaging, lesions
show variable enhancement. Occasionally, extensive
heterogeneous enhancement is seen.
Figure 13. Subcutaneous metastatic melanoma in a 68-year-old woman. (a, b) Sagittal
T1-weighted (406/17) (a) and axial gadolinium-enhanced T1-weighted (433/17) fat-suppressed
(b) SE MR images show a well-defined subcutaneous solid mass (arrow) in the posterior
aspect of the right thigh. Intense homogeneous enhancement of the mass is seen in b.
(c) Axial positron emission tomographic image of the thighs shows two hypermetabolic foci
(arrowheads) that correspond to melanoma metastases. The lesion in the right thigh correlates
with that in a and b.
Figure 14. Subcutaneous myxoma in the lower
leg of a 32-year-old man. Axial T2-weighted
(2500/90) SE MR image shows a well-defined
subcutaneous mass (*) anterior to the tibia. The
large size of the lesion makes it difficult to determine
whether its origin is in subcutaneous tissue
or the aponeurosis.
RG f Volume 27 ● Number 2 Beaman et al 519
Cutaneous lymphomas may be broadly classified
as primary (with no evidence of extracutaneous
involvement) or secondary (with evidence of
simultaneous or previous extracutaneous involvement).
They may be further subclassified according
to cell type: B cell, T cell, histiocytic, and
other (rare) (15). Primary lymphoma of soft tissue
is exceedingly rare, and patients often present
with a palpable mass that simulates a soft-tissue
sarcoma. At imaging, associated abnormalities in
adjacent osseous structures or lymph nodes often
are identified, and such findings allow the inclusion
of lymphoma in the differential diagnosis.
When lymphoma is manifested as an isolated softtissue
or subcutaneous mass, the imaging features
are nonspecific (Fig 15) (3).
Granuloma annulare is a benign inflammatory
dermatosis, with a common cutaneous form
found in adults and an uncommon subcutaneous
form found in children and adolescents. The cutaneous
form is diagnosed clinically and therefore
is rarely encountered by the radiologist, whereas
the subcutaneous form may be manifested as a
superficial mass. Radiographs show a circumscribed
nodular mass that is localized to the subcutaneous
tissues, with an absence of both bone
involvement and mineralization. The mass shows
decreased signal intensity at MR imaging and
variable enhancement after the administration of
contrast material (Fig 16).
Figure 15. Superficial B cell lymphoma in the forearm of a 53-year-old man. Axial T1-weighted
(716/9) (a) and axial T2-weighted (2350/80) fat-suppressed (b) SE MR images show a large homogeneous
mass (*) with nonspecific features in the cutaneous and subcutaneous compartments.
The mass demonstrated signal intensity slightly higher than that in skeletal muscle at T1-weighted
imaging, high signal intensity at T2-weighted imaging, and intense homogeneous enhancement at
gadolinium-enhanced MR imaging.
Table 5
Inflammatory Lesions
Diagnosis Classification Patient Age Comments
Cellulitis Cutaneous,
subcutaneous
All ages Skin thickening with reticulated fluidlike signal intensity in
the subcutaneous tissues
Fasciitis Fascial All ages Fascial thickening and enhancement
Adenitis Subcutaneous Children,
adolescents
Signal intensity is typically intermediate on T2-weighted,
non–fat-suppressed images
Abscess Subcutaneous All ages Fluidlike signal intensity, rim of enhancement
520 March-April 2007 RG f Volume 27 ● Number 2
Inflammatory Lesions
In general, the term cellulitis is used to describe an
inflammation or infection of the cutaneous and
subcutaneous tissues, without gross suppuration
(Table 5). Fasciitis is inflammation or infection of
the fascia, and adenitis is inflammation or infection
of one or more lymph nodes. Cat-scratch
disease is a common and benign form of regional
lymphadenitis that is associated with exposure to
cats. The condition is caused by infection with
Bartonella henselae, a Gram-negative bacillus.
Most of those affected are young; two-thirds of
cases occur in patients between the ages of 5
and 21 years (20). MR imaging shows regional
lymphadenopathy with surrounding edema (Fig
17) (20). Involvement of a single node is seen in
Figure 16. Granuloma annulare
in the lower leg of a
5-year-old girl. Axial T1-
weighted (500/20) (a) and
axial T2-weighted (2000/
80) (b) SE MR images show a
mass in the subcutaneous tissue
of the anterior part of the
leg (arrow). The lesion had
decreased signal intensity and
a somewhat indistinct margin
on all MR images.
Figure 17. Cat-scratch disease in a 26-year-old man with a rapidly growing, painful mass in the groin. (a) Coronal
T2-weighted (5950/68) SE MR image shows a nodal mass (arrow) in the right side of the groin, with prominent associated
edema (arrowhead). (b) Axial T1-weighted (600/15) SE MR image shows a large right inguinal node with surrounding
edema (arrow). On MR images obtained after contrast material was administered, the node demonstrated
mild heterogeneous enhancement. The findings were indicative of lymphadenopathy.
RG f Volume 27 ● Number 2 Beaman et al 521
44%–85% of patients. At MR imaging or CT,
fasciitis is characterized by fascial enhancement,
which may have various causes. Necrotizing fasciitis
is diagnosed in the presence of one or more
regions of nonenhanced fascia, a finding indicative
of nonvascularized tissue, within an otherwise
markedly enhanced fascial layer (Fig 18).
An abscess, in contradistinction, is defined as a
focal collection of pus (or necrotic tissue, white
blood cells, and bacteria) that is confined to a
specific space, tissue, or organ (21,22). An abscess
may, with time, become walled off by highly
vascularized connective tissue (23) and may be
associated with diffuse inflammation.
At MR imaging, the appearance of a soft-tissue
abscess varies with the virulence of the organism
and the host’s reaction to the organism. In general,
areas of suppuration demonstrate signal
intensity similar to that of fluid, and the internal
contents of the lesion appear relatively homogeneous.
However, the degree of homogeneity
and the signal intensity vary, depending on the
amount of internal proteinaceous debris, necrosis,
foreign matter, and gas (24). MR images depict
a lesion with a peripheral rim of variable signal
intensity that is markedly enhanced after the administration
of intravenous gadolinium (24). A
Figure 18. Necrotizing fasciitis in a 51-year-old diabetic man with rapidly progressing pain and
swelling in the thigh. (a, b) Axial T1-weighted (716/15) (a) and axial fat-suppressed T2-weighted
(6566/105) (b) SE MR images show a reticulated pattern of abnormal signal intensity within the subcutaneous
tissues, a pattern suggestive of cellulitis; an extensive region of abnormal signal intensity (*) centered
on the fascia, a finding indicative of fasciitis; and areas of abnormal signal intensity in the adjacent
muscle (arrows in b), features indicative of associated myositis. (c) Axial T1-weighted (650/15) SE MR
image obtained after the administration of intravenous gadolinium shows nonenhanced fascial tissue laterally
(*) and anteriorly. Necrosis of the fascia (necrotizing fasciitis) was identified at surgery.
522 March-April 2007 RG f Volume 27 ● Number 2
Teaching
Point
discrete abscess may be differentiated from a diffuse
inflammatory process (phlegmon) in that the
latter appears as a poorly defined region with increased
signal intensity on T2-weighted images
and with an indistinct margin (an edema-like pattern),
but without the internal high signal intensity
typically seen in a focal fluid collection.
Conclusions
Soft-tissue malignancies are relatively uncommon,
in comparison with the large number of benign
lesions that may be seen in the superficial
tissue. The imaging appearance of a superficial
mass often yields limited information to help narrow
the differential diagnosis. Therefore, not only
the imaging appearance but also the lesion location
and the patient’s age should be considered
when evaluating a superficial mass.
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RG Volume 27 • Volume 2 • March-April 2007 Beaman et al
Superficial Soft-Tissue Masses: Analysis, Diagnosis, and
Differential Considerations
Francesca D. Beaman, MD et al
Page 512
Lipomas are by far the most frequently encountered subcutaneous masses.
Page 515
It is especially noteworthy that a superficial lesion that extends through the fascia is more likely to be
a malignancy.
Page 516
The most common of these [skin appendage lesions] is probably the infundibular cyst, or epidermal
cyst. This simple epithelial cyst is lined with infundibular or epidermal-like cells that keratinize (8).
The term sebaceous cyst is a misnomer and should be avoided, because these cysts are not of
sebaceous differentiation and their imaging characteristics vary according to their internal contents.
Page 518
Metastatic melanoma may be manifested with a similar pattern of multiple subcutaneous nodular
lesions, and its presence must be considered in a patient who presents with multiple subcutaneous
nodules.
Page 522
At MR imaging, the appearance of a soft-tissue abscess varies with the virulence of the organism and
the host’s reaction to the organism.