Superficial Lipomas Lipomas are by far the most common soft tissue tumor encounteredin orthopedic oncology. There is a large number of variants, the mostcommon being the superficial subcutaneous lipoma that occurs inboth males and females in an older age group, the 5th and 6th decadeof life. Typical lesions are seen in the back, shoulder and neck. Onpalpation, these tumors have a soft non-tender characteristic. Theyoccur more commonly in obese patients, however, when patientslose weight dramatically, the size of the lipoma will not vary. Inolder patients they grow quite rapidly at first but then stop. Theynever convert into a malignant tumor at some later date. Surgicaltreatment usually consists of a cosmetic resection and the recurrencerate is less than 5%.
Case #1183 Coronal T-1 MRI 51 year male with superficial lipoma arm
Intramuscular Lipoma The intramuscular lipoma occurs in adults between the ages of30 and 60 years, and is usually found in the larger muscle groups.The tumor occurs quite gradually, without symptoms of pain, anddoes not cause disability when left untreated. It is usuallyrecognizable on routine radiographic exam, showing a well-marginated lesion with a radiodensity less than that of thesurrounding muscle. However, the best imaging study for a lipomaof muscle is the MRI which shows a diagnostic high signal,lobulated lesion on the T-1 weighted image that has the exactsame appearance as the subcutaneous fat. On the T-2 image, thelesion will be an intermediate signal and again have the exactappearance of subcutaneous fat. Histologically, the intramuscularlipoma demonstrates large lipocytes with very small pyknoticnuclei. The pathologist must be very careful to look for evidence ofatypical lipoblasts that would suggest the diagnosis of a well-differentiated liposarcoma that can coexist with a benign lipoma.
On rare occasion, lipomas can have coexistent chondroid or osseoushamartomatous elements that in the past had been classified asmesenchymomas. Surgical treatment for the intramuscular lipoma isa marginal resection, being careful to avoid damage to the neuro-vascular structures that might pass through the lipoma. Therecurrence rate is higher than for subcutaneous lipomas and rangebetween 15 and 60%.
CLASSICCase #27072 year male with anintramuscular lipomaquadriceps muscle
Spindle Cell Lipoma The spindle cell lipoma is seen more commonly in men betweenthe ages of 45 and 65 years and is typically located in the posteriorneck or shoulder area. MRI imaging demonstrates the high signalfeatures of a lipoma on the T-1 weighted image but with areas oflower signal streaking seen throughout the high signal areas wherethe fibrous tissue is located. Histologically, the spindle cell lipomalooks 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 amarginal resection and carries a minimal chance for local recurrence.
CLASSIC Case #275 CT scan 59 year male with spindle cell lipoma thigh
Case #276 64 year male with spindle cell lipoma proximal forearm
Angiolipoma The angiolipoma is another variant of the lipoma occurring usuallyin subcutaneous locations in young adult patients. It is seen mostcommonly in the forearm. These lesions may be multiple and can bepainful because of their increased vascularity. These lesion can beseen on routine radiographs when phleboliths are present in thevascular component, but the most diagnostic imaging study is theMRI that will show the high signal features of a lipoma on the T-1weighted image with the additional serpinginous low signal patternof vascular tissue streaking throughout the high signal lipomatoustissue. Treatment for this variant is a simple marginal resectionfrom which one can expect a relatively low recurrence rate.
CLASSIC Case #277 phleboliths 27 year female with angiolipoma forearm showing phleboliths and hypertrophic subadjacent radius
Sagittal T-1 MRI showing low signal serpinginous vessels running thru high signal lipoma tissue
Resection specimen showing serpinginous vessels in fat
Case #278 Coronal T-1 MRI 16 year female with angiolipoma quadriceps muscle
Diffuse Lipomatosis An extremely rare variant of the lipoma is the diffuse lipomatosisform seen during the first two years of life. It may involve oneentire extremity or the trunk, demonstrating both superficial anddeep intramuscular, multifocal lesions. Histologically, these lesionsare identical to that of a benign lipoma and because of the massiveinvolvement of the extremity in some cases, amputation may beindicated.
CLASSIC Case #280 20 year male with diffuse lipomatosis lower extremities
Lumbosacral Lipoma The lumbosacral lipoma variant is frequently associated with aspinabifida defect in the spine and can be seen in both the pediatricand 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 responseon the T-1 weighed image, like all other forms of lipomas. Treatmentconsists of a marginal surgical resection, including the lesions withinthe vertebral canal. A low recurrence rate is anticipated.
CLASSICCase #281Sagittal T-1 MRIlumbosacral lipoma61 year male
Hibernoma The hibernoma is a very rare lipoma variant seen usually in youngadults in the intrascapular area of the back. It is painless and slowgrowing and ranges between 10 and 15 cm in diameter. Histolo-logically, the hibernoma demonstrates fine granular or vaculatedcells consisting of brown fat and large amounts of glycogen. Thetreatment for this lesion is simple marginal resection with a verylow potential for local recurrence.
Case #1197CLASSIC37 year female withhibernoma triceps mSagittal T-1 MRI
Liposarcoma Second to the MFH, the liposarcoma is the most common softtissue tumor seen in the musculoskeletal system. These tumors areseen typically in an older population group (over the age of forty)and are slightly more common in males than females. They aretypically located in large muscle groups, especially in the lowerextremity where 70% of these tumors will be found. There are foursubtypes of liposarcoma, including the well-differentiated formand the myxoid form that are low grade, and the round cell andpleomorphic forms that are high grade.
Well-differentiated Liposarcoma The well-differentiated liposarcoma is a very low grade variantof the liposarcoma that looks almost like a benign lipoma. It occursin people past the age of 45 years and is commonly seen in thelower extremity, especially in the buttock and thigh area, but canalso be found in the retroperitoneal portions of the body. On grossexamination, the well-differentiated form looks like a routine intra-muscular lipoma, but microscopically the pathologist must find afew areas of low grade lipoblasts with a signet ring appearanceto make this diagnosis. This lesion is sometimes referred to as anatypical lipoma because its gross appearance is similar to the benignlipoma. The prognosis for this variant is extremely good but with afairly high potential for local recurrence in about 30-50% of cases.There is essentially no chance of this lesion metastasizing to distantparts. If located in the retroperitoneal area, it can be fatal becauseof the difficulty in removing the tumor.
CLASSICCase #283Coronal T-1 MRI63 year femaleWell-differentiatedliposarcoma thigh
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 40and 50 years of age. It occurs in the lower extremities in 75% ofcases, especially in the popliteal area. These lesions are slowgrowing and frequently asymptomatic in the early stages. Onimaging studies, the MRI is the best method for visualizing thesetumors that will have a mixed high and low signal on the T-1weighted image because of the high percentage of fatty tissue inthe tumor. Histologically, there will be evidence of malignantlipoblasts and it is common to find a plexiform network of smallcapillary tubes running thru the fatty tumor, similar to the capillaryhemangioma. The prognosis for this variant is quite good after awide local surgical resection, followed in most cases by localradiation therapy. The chance of pulmonary metastases runs ashigh as 20% and occasionally there will be multifocal myxoid
liposarcomas occurring in the extremities as well as in the retro -peritoneal locations. Occasionally, one will see a transitionalform of myxoid converting into a higher grade round cell lipo-sarcoma which carries a more guarded prognosis.
CLASSIC Case #285 Sagittal T-1 MRI 67 year female with myxoid liposarcoma knee
Round cell and Pleomorphic Liposarcoma The round cell and pleomorphic liposarcomas are high gradeliposarcomas seen in the same locations as other liposarcomas ina slightly older age group. They account for about 10% of allliposarcomas. Because these are high grade they act more like ahigh grade MFH with increased pain and rapid growth. On imagingstudies, the higher grade lesions take on the appearance of a moreaggressive sarcoma without the high signal appearance of fat onthe T-1 weighted image. Histologically, there will be evidence ofsevere atypicism and bizarre-appearing giant cells with onlyoccasional areas of lipoblastic signet ring cells that are necessaryto make the ultimate diagnosis. These high grade lesions are treatedby wide surgical resection, followed by postoperative radiationtherapy and occasionally chemotherapy will be indicated foraggressive lesions in a younger age group. The chance ofpulmonary metastases runs as high as 80% in these high gradevariants.
CLASSICCase #29038 year male withhigh grade round cellliposarcoma thigh
Hemangioma After the benign lipoma, the benign vascular tumor is the secondmost common soft tissue lesion seen in the human body. Hemangiomasare developmentally dysplastic neoplasms of the endothelial tube.They occur most commonly during childhood, more commonly infemales than males, and account for 70% of all benign tumors. Themost 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 firstfew weeks after birth. The lesion will grow rapidly for a period ofseveral months and then disappear spontaneously over a period ofseven years in about 80% of cases. These lesions are essentiallycosmetic and do not deserve any aggressive form of treatment.However, in the past, attempts at injecting them with sclerosingagents or liquid nitrogen, or using radiation therapy, made thesituation more disabling than the original lesion. A less common
form of hemangioma is the so-called cavernous hemangioma thathas a purplish-gray appearance and can look similar to varicositiesin the extremities but in a younger age group. They can involvelarge muscle groups in the extremity and can even involve synovialmembranes in joints. Radiographically, the hemangioma may present with small,punctate, calcific deposits within the tumor that is almost diagnosticof this condition. These are referred to as phleboliths. The use ofMRI technology is very helpful in making the diagnosis of a hem-angioma and the characteristic sharp mixed signal serpinginouspattern is seen clearly on the T-1 weighted images. As with thecutaneous hemangioma, the larger intramuscular hemangiomas inchildren are not very disabling but can create symptoms of paincaused by spontaneous hemorrhage into the lesion with minimalblunt trauma. The pain symptoms can usually be treated with icingdown for the first 24 hours, followed by compressive dressings fora period of two weeks, after which the patient returns to normal
activity. There may be a recurrence of these clinical symptoms onceor twice a year. Sometimes repeated hemorrhage into an intra-muscular hemangioma can result in fibrotic contracture withdeformity of the adjacent joint that might require a surgical releaseto correct the deformity. An example of this is equinous deformityof the foot caused by a hemangioma of the gastroc muscle. In thepast, attempts have been made to eradicate these larger tumors inmuscle with embolization technique, attempting to occlude the feedervessels. This can lead to compartment syndrome, severe contracturesand loss of muscle strength that can be more severe a disability thanthe original lesion. Wide surgical resection is extremely difficultbecause of the poorly defined margin to the hemangioma and, as aresult, local recurrence is common, followed by intramuscularhemorrhage and associated pain. In some cases with very largehemangiomas, amputation is indicated when severe loss of functionoccurs. It is extremely rare for a malignant conversion to occurwithin a benign vascular dysplasia.
CLASSICCase #292 14 year female hemangioma foot
Lymphangioma The Lymphangioma, like the hemangioma, is a hamartomatousdysplastic 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 verysimilar histological appearance. 90% of these lesions will occurbefore the age of two years. There is no sex predominance and themost common locations are the head and neck, axilla, inguinal areaand, in some cases, the abdominal viscera including the liver andspleen. Lymphangiomas can be classified as either the capillary typeor simplex type which are considered cutaneous lesions. Larger,deeper lesions are usually cavernous or cystic in nature and referredto as cystic hygromas.
CLASSICCase #30123 year femalelymphangioma forearmand hand withthumb gigantism
Glomus Tumor The glomus tumor and the hemangiopericytoma are vasculartumors that arise from the hemangiopericyte which is a cell at theperiphery of the capillary vascular network whose normal functionis to regulate the flow of blood thru the capillary tube system. There-fore, these are tumors that arise from cells outside the endothelialtube where hemangiomas originate from endothelial cells. Theglomus tumor is a small and usually subcutaneous tumor measuringless than 1 cm in diameter and represents 1.6% of all soft tissuetumors. It occurs equally in men and women between the ages of20 and 40 years. The most common location for the glomus tumoris 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, forearmand foot area are invisible to physical diagnosis and characteristicallypresent with localized lancinating pain that persists in the exactlocation of origin until treated by minimal wide surgical resection.
CLASSIC Case #305 50 year male with glomus tumor thumb
Hemangiopericytoma The hemangiopericytoma arises from the same hemangiopericytesin the capillary system but is a larger tumor seen in more proximalareas, usually a deep tumor in muscle bellies about the thigh orretroperitoneal area of the pelvis. The smaller tumors are usuallybenign but the larger, more aggressive pericytomas can be malignantand therefore deserve more aggressive treatment with wide resectionfollowed by postoperative radiation therapy because of the chance oflocal recurrence.
CLASSIC Case #308 Sagittal T-1 MRI 87 year female with hemangiopericytoma below groin
Kaposi’s Sarcoma Kaposi’s sarcoma is considered to be the most common of allsoft tissue malignant vascular tumors and can be divided into thechronic, lymphadenopathic, transplant associated type, and theAIDS-related type. It is a cutaneous angiosarcoma seen just beneaththe skin, presenting with a characteristic purplish-blue appearance,similar to a cutaneous hemangioma. It occurs most commonly inmen and is endemic in Central Africa where AIDS is very prevalent.The most frequent location for the Kaposi’s sarcoma is in the footand ankle area. Microscopically, the tumor has an aggressivevascular pattern but with rare mitoses. However, over a period ofyears the tumor can develop into a high grade angiosarcoma or evenfibrosarcoma. The overall mortality runs between 10 and 20%. Thetreatment usually consists of local radiation therapy or surgicalresection if the lesion is localized.
Case #312 75 year female with Kaposi’s sarcoma foot
Angiosarcoma The soft tissue angiosarcoma is an extremely rare soft tissuetumor, accounting for less than 1% of all sarcomas. It is usuallya cutaneous lesion that affects males more often than females. Itcan be deeply located, seen typically in the upper extremitiesof women who have had chronic lymphedema following radicalbreast surgery and radiation therapy. The high grade angiosarcomais not a very bloody tumor and does not have the typical vascularspaces seen in benign vascular tumors or low grade intermediateangiosarcomas. The prognosis for the high grade angiosarcoma isvery poor, especially for older people, and the treatment usuallyconsists of wide local resection and postoperative radiationtherapy.
CLASSIC Case #314 Sagittal proton density MRI 30 year male with high grade angiosarcoma heel