This pathology case presentation details the diagnosis of De-differentiated Liposarcoma (DDLPS) in a 70-year-old man presenting with a large, high-grade retroperitoneal mass partially surrounding the kidney. Radiologically, the large size and location make it critical to distinguish between primary soft tissue sarcoma and secondary involvement of adjacent organs (kidney, GI tract).
Grossly, the tumor was massive and heterogeneous, featuring areas of necrosis, hemorrhage, and mixed fleshy/gelatinous tissue. Microscopically, the diagnosis was secured by identifying the characteristic transition from a well-differentiated liposarcoma (WDLPS) component (atypical adipocytes, sclerosis) to an adjacent high-grade pleomorphic/spindle cell sarcoma component. The high-grade area exhibited diverse patterns, including mixoid change with ‘chicken wire’ vasculature and a herringbone growth pattern. The speaker emphasizes that DDLPS is the most common high-grade sarcoma in the retroperitoneum, and although it carries a high risk of local recurrence due to surgical difficulty, its metastatic rate is generally lower than other pleomorphic sarcomas.
De-differentiated Liposarcoma (DDLPS) of the Retroperitoneum
0:00:11 Case Introduction: A 70-year-old man presented with a large retroperitoneal mass partially surrounding the kidney.
0:00:24 Initial Differential Diagnosis: A high-grade sarcoma in the retroperitoneum should immediately suggest De-differentiated Liposarcoma (DDLPS) as the top diagnosis, as it is the most common sarcoma type in this site.
0:01:19 Localization Challenge: Radiographically and intraoperatively, it is often difficult to definitively determine if a large retroperitoneal mass originated from soft tissue (sarcoma) or an adjacent organ (like the kidney, GI, or GYN structures) with secondary involvement.
0:02:33 Gross Appearance: The excised mass was enormous, highly heterogeneous, and exhibited areas that were gelatinous, yellow, fleshy white, and marked by extensive hemorrhage and necrosis.
0:03:21 Microscopic Heterogeneity: The high-grade component showed diverse architectural patterns, including atypical fusiform spindle cells, mixoid backgrounds, delicate branching ('chicken wire') vessels (mimicking Mixoid Liposarcoma), and a herringbone pattern (0:04:31).
0:06:04 Diagnostic Requirement: The diagnosis of DDLPS requires the presence of an area of Well-Differentiated Liposarcoma (WDLPS) (atypical hyperchromatic cells, scattered lipoblasts, and sclerosis of fat) transitioning into an adjacent high-grade sarcoma component.
0:07:47 Molecular Confirmation: If the WDLPS component is not identified (due to complete overgrowth by the high-grade component), the diagnosis can be confirmed by FISH demonstrating MDM2 amplification.
0:08:29 DDLPS Variability: The high-grade, de-differentiated component of DDLPS is highly pleomorphic and can differentiate into almost any type of sarcoma pattern, including heterologous differentiation like osteosarcoma or rhabdomyosarcoma.
0:09:40 Clinical Takeaway: DDLPS in the retroperitoneum is difficult to cure because the tumors are often large when discovered, making complete surgical resection challenging, resulting in a very high rate of local recurrence.
0:10:24 Prognosis Insight: Despite appearing aggressive microscopically, DDLPS has a lower 5-year metastatic rate (estimated around 20%) compared to other high-grade adult sarcomas (e.g., Pleomorphic Liposarcoma, which is around 50%).