Liposarcoma |
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Large fungating, ulcerated liposarcoma of the
tongue is lobulated and has a yellowish color. This was a rapidly enlarging lesion. |
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Quick Review for Patients
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The liposarcoma is a malignancy of fat cells. In adults it is the most common soft tissue sarcoma but it is rare in and around the mouth. It normally appears in a middle-aged person as a slowly enlarging, painless and nonulcerated submucosal mass but some lesions grow rapidly and become ulcerated early in their growth. Treatment is radical surgical removal and survival after treatment is largely dependent on the size of the tumor and the exact microscopic type of the tumor. Overall 5-year survival is less than 50%. |
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Liposarcoma, the malignancy of adipocytes, was
first described by Virchow in the 1860s. It is the most common soft
tissue sarcoma, comprising approximately 17% of all sarcomas, and 3% of all
liposarcomas occur in the head and neck region, usually in the neck and cheek
areas. Oral involvement is decidedly rare and the trunk and lower extremities
are the most likely sites of tumor development. No well-established causative
factor has been identified, although trauma has been implicated. Development
from a preexisting benign lipoma is very rare and most cases arise de
novo. It most frequently arises from the deep-seated stroma rather than
from submucosal or subcutaneous fat. As of the year 2000, fewer than 50
oral examples had been reported.
Clinical Features
Oral liposarcoma can develop at any age but most cases occur in middle-aged individuals, with an average age of 45 years. This is approximately a decade earlier than liposarcoma development in other anatomic sites. The tumor has a slight male predilection, but the number of reported cases is small and this may reflect a case-selection bias. The typical example is a slowly enlarging, painless, deep, moderately soft mass without surface ulceration or hemorrhage. Occasional cases grow with alarming rapidity and ulcerate early, however, and these tend to metastasize very early as well (Figure 2). Any oral site may be affected, but the most commonly involved sites are the cheek, floor of mouth, lips and soft palate.
Transillumination may show an area of decreased density, but MRI is the best imaging method for identifying and outlining the lesion. The fatty tissue of liposarcoma gives a bright signal on T1-weighted MRI images, with progressively decreasing signal on T2-weighted images. Fat-suppression images show signal dropout within the neoplastic mass.
Pathology and Differential Diagnosis
The liposarcoma demonstrates considerable microscopic variability and the biological behavior of the tumor is greatly dependent on the exact histopathologic appearance. In fact, Enzinger and Weiss have stated that, "Diagnosis of liposarcoma without further qualification as to the exact histological type is meaningless." Well-differentiated liposarcoma (Figure 3) represents 5-15% of all liposarcomas and is often so mature in appearance and so innocuous in its clinical behavior that some authorities advocate using the term atypical lipoma for those located in superficial dermal or mucosal regions. The lesion is composed of broad sheets and streaks of adipocytes admixed with occasional lipoblasts, separated by fibrous septa containing spindle cells with hyperchromatic and mildly pleomorphic nuclei. Signet-ring cells are usually present and are important to the diagnosis; multivacuolar lipoblasts may be seen as well.
The size of available fat cells is variable and some lesions are infiltrated by a small to moderate number of chronic inflammatory cells (well differentiated inflammatory liposarcoma). Some tumors show lesional cells within a matrix of loose or moderately dense collagenic fibers (well-differentiated sclerosing liposarcoma). In the absence of inflammatory and sclerosing features, the term well-differentiated "lipoma-like" liposarcoma has been applied.
The less well-differentiated lesions are typically subclassified into one of 4 categories: myxoid, round cell, pleomorphic, or dedifferentiated liposarcoma. The myxoid liposarcoma (Figure 4) represents half of all liposarcomas and is composed of variably mature multivacuolar and univacuolar lipoblasts, often with numerous signet-ring types scattered throughout a myxomucinous stroma with a sparse or sometimes abundant fibrillar network (Figure 4). A delicate network of intertwining small capillaries is also seen. The stroma is rich in nonsulfated glycosaminoglycans and there is a lobular pattern to the tissue. Lesional cells may be rounded or spindled, and in the less differentiated tumors the spindle forms may proliferate so extensively that the appearance of the tissue closely resembles the primitive mesenchymal proliferation of the malignant mesenchymoma. Most cases, however, are relatively well differentiated and the usual diagnostic dilemma is between well-differentiated liposarcoma, myxoid liposarcoma and myxoid lipoma. Multinucleated lipoblasts may be present in small numbers, as may mitotic figures. Focal chondroid and osseous metaplasia may be seen.
Round cell liposarcoma (Figure 5), also known as poorly differentiated myxoid liposarcoma represents 10-20% of all liposarcomas. This very aggressive variant is probably a poorly differentiated myxoid liposarcoma, with many more cells, with a loss of the vascular network and lobular pattern, and with very little lipid within lesional cells . Transition toward myxoid liposarcoma and the occasional signet ring cell may be the key identifying feature. The round cells have a small to moderate amount of finely vacuolated or granular cytoplasm and may appear epithelioid or pericytoid.
Pleomorphic liposarcoma (Figure 6) represents 25-35% of all liposarcomas and is characterized by a disorderly growth pattern, extreme cellularity and extreme cellular pleomorphism, including bizarre giant cells. Lesional cells are polygonal or stellate with pale eosinophilic cytoplasm and poorly-demarcated cell boundaries. These are interspersed with giant lipoblasts containing greatly enlarged, very hyperchromatic, angular or globular nuclei. The latter cells are reminiscent of the giant cells of pleomorphic rhabdomyosarcoma and malignant fibrous histiocytoma. Uncoalesced lipid droplets may be seen in the giant cells, but this is not common.
Dedifferentiated liposarcoma is characterized by an admixture of well-differentiated and poorly-differentiated lipoblastic components. This is extremely rare in the oral region and is more common in the retroperitoneum and the extremities. The undifferentiated component can resemble a round cell or pleomorphic liposarcoma, and two-thirds of cases bear a strong resemblance to malignant fibrous histiocytoma.
Stains for lipids are often useful in the diagnosis of liposarcoma, but this material may be scarce and is sometimes produced by unrelated mesenchymal and epithelial neoplasms. The mucinous matrix, when present, will stain with alcian blue and is metachromatic with toluidine blue and cresyl violet stains; it is weakly positive with Meyer’s mucicarmine stain. Intracellular glycogen (diastase-sensitive, PAS positive) may be seen in some lesional cells. Adipocytes and lipoblasts react positively for vimentin and S-100 protein immunostains, but these vary in intensity and may not be expressed in poorly differentiated lesions. Smooth muscle actin may also be immunoreactive in some lesional cells and is present in all liposarcomas showing smooth muscle differentiation.
Treatment and Prognosis
Liposarcoma of the oral region is typically treated by wide local excision. Radiotherapy may be used to control local recurrence and lessen the risk of metastasis. Five-year survival rates are similar to those of other anatomic sites and are very much dependent on lesional size and the histopathologic grade or subtype. Patients with well differentiated lesions seldom experience metastasis and have an excellent 85-100% 5-year survival, while those with myxoid liposarcoma have a somewhat lesser survival rate (75-95%) and those with round cell and pleomorphic liposarcoma show an even worse survival rate (20-50%), with frequent metastasis and local recurrence. Those with dedifferentiated liposarcoma have a 30% 5-year survival rate.
References (Chronologic Order)
Note: General references can be found by clicking on that topic to the left.
Sauk JJ Jr. Liposarcoma of the head and neck. J Oral Surg 1971; 29:38-40.
Sadeghi EM, Sauk JJ. Liposarcoma of the oral cavity: clinical, tissue culture, and ultrastructure study of a case. J Oral Pathol 1982; 11:263-275.
Garavaglia J, Gnepp DR. Intramuscular (infiltrating) lipoma of the tongue. Oral Surg Oral Med Oral Pathol 1987; 63:348-350.
Eidinger G, Katsikeris N, Gullane PI. Liposarcoma: report of a case and review of the literature. J Oral Maxillofac Surg 1990; 48:984-988.
Guest PG. Liposarcoma of the tongue: a case report and review of the literature. Br j Oral Maxillofac Surg 1992; 30:268-269.
McCulloch TM, Makielski KH, McNutt MA. Head & neck liposarcoma: a histopathologic reevaluation of reported cases. Arch Otolaryngol Head Neck Surg 1992; 118:1045-1049.
Stewart M, Schwartz M, Alford B. Atypical and malignant lipomatous lesions of the head and neck. Arch Otolaryngol Head Neck Surg 1994; 120:1151-1155.
Zheng J, Wang Y. Liposarcoma in the oral and maxillofacial region: an analysis of 10 consecutive patients. J Oral Maxillofac Surg 1994; 52:595-598.
Kacker A, Taskin M. Atypical intramuscular lipoma of the tongue. Oral Surg Oral Med Oral Pathol 1996; 110:189-191.
Allen PW, Strungs I, MacCormac LB. Atypical subcutaneous fatty tumors: a review of 37 referred cases. Pathol 1998; 30:123-135.
Kamikaidou N, Kirita T, Kenji M, Masahito S. Liposarcoma of the check: report of a case. J Oral Maxillofac Surg 1998; 662-665.
Gagari E, Kabani S, Gallagher G. Intraoral liposarcoma: case report and review of the literature. Oral Surg Oral Med Oral Pathol 2000; 89:66-72.
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Figure 4: Myxoid liposarcoma. [return to text] |
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Figure 5: Round cell liposarcoma. [return to text] | |
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Figure 6: Pleomorphic liposarcoma. [return to text] | |
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