summary Liposarcomas are a heterogeneous class of sarcomas with differentiation towards adipose tissue that consist of 5 different sub-types: well-differentiated, myxoid, round cell, pleomorphic, and dedifferentiated. The condition is typically seen in patients 50-80 years of age who present with a slow-growing, painless mass. Diagnosis is made with a biopsy showing immature lipoblasts with various cellular atypia depending on the sub-type. Treatment may be marginal excision for a well-differentiated liposarcoma. Wide surgical resection with radiation is indicated for intermediate and high-grade liposarcomas. Epidemiology Incidence liposarcomas are the second most common form of soft tissue sarcomas in adults Demographics occur in older individuals (50-80yrs) affect more males than females Anatomic location tend to occur deep to fascia more common in lower extremity than upper extremity common in retroperitoneum Etiology Pathophysiology the lipoblast (signet ring-type cell) is a hallmark of liposarcomas Genetics well-differentiated liposarcoma - amplification (MDM2) myxoid liposarcoma - translocation (12;16) Malignant potential metastasis risk correlates with grade/sub-type of liposarcoma low grade (well-differentiated) has a metastasis rate of < 1% intermediate grade (myxoid) has a metastasis rate of 10-30% high grade has a metastasis rate of > 50% Classification Histologic types liposarcoma types are related to the developmental stage of the lipoblasts from which they form all are from primitive mesenchymal cells types include well-differentiated same entity as atypical lipomatous tumor myxoid most common ~ 50% of all liposarcomas round cell pleomorphic dedifferentiated Imaging Plain Radiographs may show soft tissue calcification or ossification in well-differentiated liposarcomas MRI well-differentiated liposarcomas look similar to lipomas on MRI bright on T1, dark on T2 may show differences in rate of growth, stranding, size high-grade liposarcomas look similiar to other sarcomas on MRI dark on T1, bright on T2 although high grade liposarcomas appear fibrogenic, they may have 10% fat composition, so they appear dark on T1 and bright on T2 unlike a lipoma which images iso-intense to sub-cutaneous fat on all sequences CT Chest/Abd/Pelvis myxoid liposarcomas have a tendency for abnormal metastasis outside of the lungs therefore, histologic diagnosis of myxoid liposarcoma should be evaluated with CT chest/Abd/Pelvis Histology Characteristic histology immature lipoblasts (signet ring-type cells) mature adipocytes Atypical lipomatous tumor (ALT; located in extremities) referred to as well-differentiated liposarcoma (WDL) when located central/retroperitoneal - WDLs have a higher risk of local recurrence and metastatic spread compared to ALTs low grade atypical lipoblasts, minimally cellular fatty stroma background stain for MDM2/CDK4 have ring chromosome 12 Myxoid liposarcoma low to intermediate grade proliferating lipoblasts upon a myxoid stroma matrix signet ring lipoblasts may occur Round cell liposarcoma poorly differentiated liposarcoma with characteristic small round blue cells Pleomorphic liposarcoma high-grade pleomorphic tumor giant lipoblasts with bizarre nuclei Dedifferentiated liposarcoma high-grade sarcoma adjacent to well-differentiated lipomatous lesion Treatment Operative marginal resection without radiotherapy indications atypical lipomatous tumors (ALT) outcomes low risk of local recurrence, metastasis extremely rare dedifferentiation risk of 2% in extremities (ALTs) and 20% in retroperitoneal lesions (well-differentiated liposarcomas) wide surgical resection with adjuvant radiotherapy indications intermediate grade liposarcomas high grade liposarcomas outcomes radiation decreases local recurrence chemotherapy may be beneficial in selected patients myxoid liposarcomas with >10% round cells have high likelihood of metastasis Prognosis Lipomas do not predispose a patient to a liposarcoma Well-differentiated liposarcomas exhibit < 10% local recurrence rates and <1% chance of metastasis and almost complete survival With appropriate treatment, intermediate and high grade liposarcomas show ~ 20% risk of local recurrence but they exhibit 5 year survival between 25 - 50%