5. Superficial Lipomas
Lipomas are by far the most common soft tissue tumor encountered
in orthopedic oncology. There is a large number of variants, the most
common being the superficial subcutaneous lipoma that occurs in
both males and females in an older age group, the 5th and 6th decade
of life. Typical lesions are seen in the back, shoulder and neck. On
palpation, these tumors have a soft non-tender characteristic. They
occur more commonly in obese patients, however, when patients
lose weight dramatically, the size of the lipoma will not vary. In
older patients they grow quite rapidly at first but then stop. They
never convert into a malignant tumor at some later date. Surgical
treatment usually consists of a cosmetic resection and the recurrence
rate is less than 5%.
6. Case #1183 Coronal T-1 MRI
51 year male with superficial lipoma arm
15. Intramuscular Lipoma
The intramuscular lipoma occurs in adults between the ages of
30 and 60 years, and is usually found in the larger muscle groups.
The tumor occurs quite gradually, without symptoms of pain, and
does not cause disability when left untreated. It is usually
recognizable on routine radiographic exam, showing a well-
marginated lesion with a radiodensity less than that of the
surrounding muscle. However, the best imaging study for a lipoma
of muscle is the MRI which shows a diagnostic high signal,
lobulated lesion on the T-1 weighted image that has the exact
same appearance as the subcutaneous fat. On the T-2 image, the
lesion will be an intermediate signal and again have the exact
appearance of subcutaneous fat. Histologically, the intramuscular
lipoma demonstrates large lipocytes with very small pyknotic
nuclei. The pathologist must be very careful to look for evidence of
atypical lipoblasts that would suggest the diagnosis of a well-
differentiated liposarcoma that can coexist with a benign lipoma.
16. On rare occasion, lipomas can have coexistent chondroid or osseous
hamartomatous elements that in the past had been classified as
mesenchymomas. Surgical treatment for the intramuscular lipoma is
a marginal resection, being careful to avoid damage to the neuro-
vascular structures that might pass through the lipoma. The
recurrence rate is higher than for subcutaneous lipomas and range
between 15 and 60%.
79. Spindle Cell Lipoma
The spindle cell lipoma is seen more commonly in men between
the ages of 45 and 65 years and is typically located in the posterior
neck or shoulder area. MRI imaging demonstrates the high signal
features of a lipoma on the T-1 weighted image but with areas of
lower signal streaking seen throughout the high signal areas where
the fibrous tissue is located. Histologically, the spindle cell lipoma
looks like any other lipoma except for the presence of benign-
appearing fibrous tissue with occasional areas of gelatinous break-
down in the fibrous tissue. The treatment for this variant is a
marginal resection and carries a minimal chance for local recurrence.
80. CLASSIC Case #275 CT scan
59 year male with spindle cell lipoma thigh
81. Case #276
64 year male with spindle cell lipoma proximal forearm
86. Angiolipoma
The angiolipoma is another variant of the lipoma occurring usually
in subcutaneous locations in young adult patients. It is seen most
commonly in the forearm. These lesions may be multiple and can be
painful because of their increased vascularity. These lesion can be
seen on routine radiographs when phleboliths are present in the
vascular component, but the most diagnostic imaging study is the
MRI that will show the high signal features of a lipoma on the T-1
weighted image with the additional serpinginous low signal pattern
of vascular tissue streaking throughout the high signal lipomatous
tissue. Treatment for this variant is a simple marginal resection
from which one can expect a relatively low recurrence rate.
87. CLASSIC Case #277
phleboliths
27 year female with angiolipoma forearm showing
phleboliths and hypertrophic subadjacent radius
88. Sagittal T-1 MRI showing low signal serpinginous
vessels running thru high signal lipoma tissue
116. Diffuse Lipomatosis
An extremely rare variant of the lipoma is the diffuse lipomatosis
form seen during the first two years of life. It may involve one
entire extremity or the trunk, demonstrating both superficial and
deep intramuscular, multifocal lesions. Histologically, these lesions
are identical to that of a benign lipoma and because of the massive
involvement of the extremity in some cases, amputation may be
indicated.
117. CLASSIC Case #280
20 year male with diffuse lipomatosis lower extremities
121. Lumbosacral Lipoma
The lumbosacral lipoma variant is frequently associated with a
spinabifida defect in the spine and can be seen in both the pediatric
and adult age group. These lesions can be associated with both intra-
dural and extradural lipomas and can result in neurological deficiency.
The MRI image will show the characteristic high signal response
on the T-1 weighed image, like all other forms of lipomas. Treatment
consists of a marginal surgical resection, including the lesions within
the vertebral canal. A low recurrence rate is anticipated.
133. Hibernoma
The hibernoma is a very rare lipoma variant seen usually in young
adults in the intrascapular area of the back. It is painless and slow
growing and ranges between 10 and 15 cm in diameter. Histolo-
logically, the hibernoma demonstrates fine granular or vaculated
cells consisting of brown fat and large amounts of glycogen. The
treatment for this lesion is simple marginal resection with a very
low potential for local recurrence.
151. Liposarcoma
Second to the MFH, the liposarcoma is the most common soft
tissue tumor seen in the musculoskeletal system. These tumors are
seen typically in an older population group (over the age of forty)
and are slightly more common in males than females. They are
typically located in large muscle groups, especially in the lower
extremity where 70% of these tumors will be found. There are four
subtypes of liposarcoma, including the well-differentiated form
and the myxoid form that are low grade, and the round cell and
pleomorphic forms that are high grade.
153. Well-differentiated Liposarcoma
The well-differentiated liposarcoma is a very low grade variant
of the liposarcoma that looks almost like a benign lipoma. It occurs
in people past the age of 45 years and is commonly seen in the
lower extremity, especially in the buttock and thigh area, but can
also be found in the retroperitoneal portions of the body. On gross
examination, the well-differentiated form looks like a routine intra-
muscular lipoma, but microscopically the pathologist must find a
few areas of low grade lipoblasts with a signet ring appearance
to make this diagnosis. This lesion is sometimes referred to as an
atypical lipoma because its gross appearance is similar to the benign
lipoma. The prognosis for this variant is extremely good but with a
fairly high potential for local recurrence in about 30-50% of cases.
There is essentially no chance of this lesion metastasizing to distant
parts. If located in the retroperitoneal area, it can be fatal because
of the difficulty in removing the tumor.
161. Case #1198.1 Dedifferentiated lipsosarcoma
Coronal T-1 MRI of
the thigh of a 41 year
male with prior history
of partially resected
atypical lipoma 3 yrs
before
165. Myxoid Liposarcoma
The myxoid variant is the most common variant of the lipo-
sarcoma and it is seen in a slightly younger age group between 40
and 50 years of age. It occurs in the lower extremities in 75% of
cases, especially in the popliteal area. These lesions are slow
growing and frequently asymptomatic in the early stages. On
imaging studies, the MRI is the best method for visualizing these
tumors that will have a mixed high and low signal on the T-1
weighted image because of the high percentage of fatty tissue in
the tumor. Histologically, there will be evidence of malignant
lipoblasts and it is common to find a plexiform network of small
capillary tubes running thru the fatty tumor, similar to the capillary
hemangioma. The prognosis for this variant is quite good after a
wide local surgical resection, followed in most cases by local
radiation therapy. The chance of pulmonary metastases runs as
high as 20% and occasionally there will be multifocal myxoid
166. liposarcomas occurring in the extremities as well as in the retro -
peritoneal locations. Occasionally, one will see a transitional
form of myxoid converting into a higher grade round cell lipo-
sarcoma which carries a more guarded prognosis.
167. CLASSIC Case #285 Sagittal T-1 MRI
67 year female with myxoid liposarcoma knee
220. Round cell and Pleomorphic Liposarcoma
The round cell and pleomorphic liposarcomas are high grade
liposarcomas seen in the same locations as other liposarcomas in
a slightly older age group. They account for about 10% of all
liposarcomas. Because these are high grade they act more like a
high grade MFH with increased pain and rapid growth. On imaging
studies, the higher grade lesions take on the appearance of a more
aggressive sarcoma without the high signal appearance of fat on
the T-1 weighted image. Histologically, there will be evidence of
severe atypicism and bizarre-appearing giant cells with only
occasional areas of lipoblastic signet ring cells that are necessary
to make the ultimate diagnosis. These high grade lesions are treated
by wide surgical resection, followed by postoperative radiation
therapy and occasionally chemotherapy will be indicated for
aggressive lesions in a younger age group. The chance of
pulmonary metastases runs as high as 80% in these high grade
variants.
238. Case #1203.1 Pleomorphic liposarcoma Axial CT scan
65 year male with recent onset buttock tumor mass in area of previous
resected large benign lipoma 6 years ago
244. Hemangioma
After the benign lipoma, the benign vascular tumor is the second
most common soft tissue lesion seen in the human body. Hemangiomas
are developmentally dysplastic neoplasms of the endothelial tube.
They occur most commonly during childhood, more commonly in
females than males, and account for 70% of all benign tumors. The
most common type of hemangioma is the solitary capillary hem-
angioma that appears as an elevated red to purple cutaneous lesion,
usually in the head and neck area. It is usually seen during the first
few weeks after birth. The lesion will grow rapidly for a period of
several months and then disappear spontaneously over a period of
seven years in about 80% of cases. These lesions are essentially
cosmetic and do not deserve any aggressive form of treatment.
However, in the past, attempts at injecting them with sclerosing
agents or liquid nitrogen, or using radiation therapy, made the
situation more disabling than the original lesion. A less common
245. form of hemangioma is the so-called cavernous hemangioma that
has a purplish-gray appearance and can look similar to varicosities
in the extremities but in a younger age group. They can involve
large muscle groups in the extremity and can even involve synovial
membranes in joints.
Radiographically, the hemangioma may present with small,
punctate, calcific deposits within the tumor that is almost diagnostic
of this condition. These are referred to as phleboliths. The use of
MRI technology is very helpful in making the diagnosis of a hem-
angioma and the characteristic sharp mixed signal serpinginous
pattern is seen clearly on the T-1 weighted images. As with the
cutaneous hemangioma, the larger intramuscular hemangiomas in
children are not very disabling but can create symptoms of pain
caused by spontaneous hemorrhage into the lesion with minimal
blunt trauma. The pain symptoms can usually be treated with icing
down for the first 24 hours, followed by compressive dressings for
a period of two weeks, after which the patient returns to normal
246. activity. There may be a recurrence of these clinical symptoms once
or twice a year. Sometimes repeated hemorrhage into an intra-
muscular hemangioma can result in fibrotic contracture with
deformity of the adjacent joint that might require a surgical release
to correct the deformity. An example of this is equinous deformity
of the foot caused by a hemangioma of the gastroc muscle. In the
past, attempts have been made to eradicate these larger tumors in
muscle with embolization technique, attempting to occlude the feeder
vessels. This can lead to compartment syndrome, severe contractures
and loss of muscle strength that can be more severe a disability than
the original lesion. Wide surgical resection is extremely difficult
because of the poorly defined margin to the hemangioma and, as a
result, local recurrence is common, followed by intramuscular
hemorrhage and associated pain. In some cases with very large
hemangiomas, amputation is indicated when severe loss of function
occurs. It is extremely rare for a malignant conversion to occur
within a benign vascular dysplasia.
332. Lymphangioma
The Lymphangioma, like the hemangioma, is a hamartomatous
dysplastic lesion of soft tissue that arises from the endothelial tube.
Instead of being filled with blood like in the hemangioma, the lymph-
angioma is filled with lymphatic fluid, but otherwise it has a very
similar histological appearance. 90% of these lesions will occur
before the age of two years. There is no sex predominance and the
most common locations are the head and neck, axilla, inguinal area
and, in some cases, the abdominal viscera including the liver and
spleen. Lymphangiomas can be classified as either the capillary type
or simplex type which are considered cutaneous lesions. Larger,
deeper lesions are usually cavernous or cystic in nature and referred
to as cystic hygromas.
353. Glomus Tumor
The glomus tumor and the hemangiopericytoma are vascular
tumors that arise from the hemangiopericyte which is a cell at the
periphery of the capillary vascular network whose normal function
is to regulate the flow of blood thru the capillary tube system. There-
fore, these are tumors that arise from cells outside the endothelial
tube where hemangiomas originate from endothelial cells. The
glomus tumor is a small and usually subcutaneous tumor measuring
less than 1 cm in diameter and represents 1.6% of all soft tissue
tumors. It occurs equally in men and women between the ages of
20 and 40 years. The most common location for the glomus tumor
is in the subungual area of a digit where it is readily visible,
exquisitely tender on palpation and has a reddish-purple color.
Subcutaneous glomus tumors that occur in the hand, wrist, forearm
and foot area are invisible to physical diagnosis and characteristically
present with localized lancinating pain that persists in the exact
location of origin until treated by minimal wide surgical resection.
354. CLASSIC Case #305
50 year male with glomus tumor thumb
361. Hemangiopericytoma
The hemangiopericytoma arises from the same hemangiopericytes
in the capillary system but is a larger tumor seen in more proximal
areas, usually a deep tumor in muscle bellies about the thigh or
retroperitoneal area of the pelvis. The smaller tumors are usually
benign but the larger, more aggressive pericytomas can be malignant
and therefore deserve more aggressive treatment with wide resection
followed by postoperative radiation therapy because of the chance of
local recurrence.
362. CLASSIC Case #308 Sagittal T-1 MRI
87 year female with hemangiopericytoma below groin
379. Kaposi’s Sarcoma
Kaposi’s sarcoma is considered to be the most common of all
soft tissue malignant vascular tumors and can be divided into the
chronic, lymphadenopathic, transplant associated type, and the
AIDS-related type. It is a cutaneous angiosarcoma seen just beneath
the skin, presenting with a characteristic purplish-blue appearance,
similar to a cutaneous hemangioma. It occurs most commonly in
men and is endemic in Central Africa where AIDS is very prevalent.
The most frequent location for the Kaposi’s sarcoma is in the foot
and ankle area. Microscopically, the tumor has an aggressive
vascular pattern but with rare mitoses. However, over a period of
years the tumor can develop into a high grade angiosarcoma or even
fibrosarcoma. The overall mortality runs between 10 and 20%. The
treatment usually consists of local radiation therapy or surgical
resection if the lesion is localized.
380. Case #312
75 year female with Kaposi’s sarcoma foot
387. Angiosarcoma
The soft tissue angiosarcoma is an extremely rare soft tissue
tumor, accounting for less than 1% of all sarcomas. It is usually
a cutaneous lesion that affects males more often than females. It
can be deeply located, seen typically in the upper extremities
of women who have had chronic lymphedema following radical
breast surgery and radiation therapy. The high grade angiosarcoma
is not a very bloody tumor and does not have the typical vascular
spaces seen in benign vascular tumors or low grade intermediate
angiosarcomas. The prognosis for the high grade angiosarcoma is
very poor, especially for older people, and the treatment usually
consists of wide local resection and postoperative radiation
therapy.
388. CLASSIC Case #314 Sagittal proton density MRI
30 year male with high grade angiosarcoma heel
