Liposarcoma is one of the most common soft tissue sarcomas in adults, accounting for the second most common of all, with the vast majority occurring in the extremities and retroperitoneal sites, rare in children, and only 2-3.76% of all cases occurring in the head and neck. The most important etiologies include trauma, genetics and radiation. Autosomal dominant disorders such as familial cancer syndrome and neurofibromatosis are associated with a high risk of transformation of liposarcoma.
1.Pathology
The tumors are mostly lobulated and nodular, with intermittent envelope visible, largely yellow or off-white in color, with delicate cut surface, resembling liposarcoma in appearance but harder in texture than liposarcoma, and their cut surface is dark red due to hemorrhage and blood vessels, with mucus component visible in about half of liposarcomas. Because of the diverse histological patterns of liposarcoma, the pathological histology classifies them into the following five types: highly differentiated, mucinous, round cell, pleomorphic, and dedifferentiated.
The pathological characteristics of each type are described below.
(1) Highly differentiated liposarcoma
It is a large lobulated lesion with more fibrin, jelly-like areas and punctate hemorrhage. Microscopically, a large number of differentiated mature adipocyte-like cells can be seen in the form of a single vacuole “ring”, and occasionally mucus areas and stellate and spindle-shaped adipocytes can be seen.
Highly differentiated liposarcoma is divided into 3 subtypes: lipomatous liposarcoma, sclerosing liposarcoma, and inflammatory cellular liposarcoma. These three subtypes have common features of liposarcoma, but each has its own characteristics.
(2) Mucinous-type liposarcoma
It accounts for about 26C78% of liposarcoma and is the most common type.
(3) Round cell type liposarcoma
About 9C10% of liposarcoma, the tumor cells are mostly round, smaller than normal fat cells, and eosinophilic granules and fat vacuoles can be seen in the cytoplasm.
(4) Polymorphic liposarcoma
This type is the least common type of liposarcoma, mostly seen in the elderly, and is characterized microscopically by the presence of two related but different tissue types in the same tumor, with significant cellular pleomorphism.
(5) Dedifferentiated liposarcoma
This type is the rarest, and is characterized by a multinodular mass with a yellow or grayish-yellow color. Microscopically, it can be seen as a non-fat-derived sarcoma-like area in a well-differentiated liposarcoma, and the morphology of tumor cells in this area can be classified as hypodifferentiated spindle cells, or it can resemble pleomorphic fibrosarcoma or malignant fibrous histiocytoma. In dedifferentiated liposarcoma, two or more malignant tissue components are present within the tumor, hence the term mixed liposarcoma. It should be distinguished from fibrosarcoma, rhabdomyosarcoma and malignant fibrous histiocytoma clinically and pathologically.
2.Clinical manifestations
Liposarcoma is mostly seen in adults, mostly at the age of 40-60 years, and is rare in children, with a higher incidence in men than in women. The incidence of liposarcoma in the head and neck varies, for example, in the subcutaneous soft tissue, larynx, hypopharynx and esophagus.
The clinical signs and symptoms of patients are closely related to the location and stage of the tumor. In the early stage, the tumor appears as a slow-growing soft tissue mass in the head and neck, which can be easily misdiagnosed as a common lipoma or neurofibroma. At the later stage, the tumor grows rapidly and the patient comes to the doctor, then the tumor is mostly in advanced stage and compression symptoms may appear, such as hoarseness caused by the tumor pressing on the recurrent laryngeal nerve and difficulty in breathing caused by the pressure on the thyroid gland.
3.Treatment and prognosis
The treatment principle of liposarcoma is a comprehensive treatment mainly based on surgery, which should be widely excised. After surgery, chemotherapy and radiation therapy should be given. For those who invade important nerves or blood vessels and cannot be enlarged, postoperative radiotherapy or radiotherapy alone is feasible. On the other hand, the effectiveness of chemotherapy in the treatment of liposarcoma of the head and neck has not been confirmed in the literature.
Although liposarcoma mostly exhibits an intact envelope, this fibrous outer membrane is not a true envelope, so careful and extensive radical resection should be performed, and cervical lymph node dissection is generally not performed because lymph node metastasis is rare. The extent of tumor resection and the relationship between the tumor and the surrounding important vascular and neural structures are positively correlated, and the invasion of important anatomical structures may hinder the surgical procedure. Because the tumor infiltrates the surrounding tissues extensively, has no obvious envelope and grows along the tissue gap, it is easy to recur after surgery. Recurrence rates can reach 80%, and several studies have demonstrated that liposarcoma is sensitive to radiotherapy. Although surgery combined with radiotherapy cannot improve the overall survival rate and metastasis rate, it can significantly reduce the postoperative recurrence rate by 40-60%.
Pathologic staging and tumor stage are the most important predictors of healing. The literature reports that highly differentiated liposarcoma and mucinous liposarcoma rarely develop distant metastases even if complete resection is not possible with surgery, and their cure rates reach 25%. Polymorphic and round cell liposarcomas are more aggressive and have a high recurrence rate, with 5-year survival rates usually not exceeding 50%.