Shreyaskumar R. Patel, MD: Different Types of Liposarcoma

What are the different types of liposarcomas, and how do they differ?

Liposarcoma is one of the more common subsets of soft tissues sarcomas and tends to be a heterogeneous group of tumors. Starting off again from a spectrum perspective of fatty tumors, lipomas are typically the benign tumors. These don’t transform or degenerate into a malignancy — a lipoma tends remains a lipoma. But, within the malignant spectrum of these fatty tumors are the lipomatous tumors. You have a low grade or grade 1 variant called atypical lipomatous tumor, which used to be called a differentiated liposarcoma. This by itself does not have any metastatic potential, but over a period of time can undergo dedifferentiation or transformation into a higher grade tumor.

The intermediate grade tumor would be a mixoid liposarcoma. These can be more aggressive with a higher proportion of what is called "round cell component." Then there are the high-grade liposarcomas, which would include pleomorphic liposarcomas and the dedifferentiated liposarcomas, where the well differentiated liposarcoma transformed into a higher grade spindle cell sarcoma, thus rendering the clinical diagnosis of a dedifferentiated liposarcoma.

It's not unusual that when we get questions about a patient with a liposarcoma, we would have to first start off by asking if they can please clarify what type of liposarcoma we are talking about, because the biology and clinical behavior are different and metastatic patterns can be different. Certainly, there may also be some therapeutic significance in each one of these subsets that would be quite relevant for a given patient.

CASE: Soft-Tissue Sarcoma Case 2

Michael C is a 59-year-old social worker from Los Angeles California; his medical history is notable for obesity, COPD, and mild hypertension.

• In January of 2014, he presents to his PCP with complaints of right lower leg pain of several weeks’ duration
• Physical exam was unremarkable except for swelling of the lower right calf; x-ray of the affected leg was negative for fracture
• MRI scan of the lower right calf showed a 20 cm well defined lobular mass arising between the gastrocnemius and soleus
• Biopsy of the mass showed myxoid liposarcoma with round cell component. Patient underwent en bloc resection of the tumor following preoperative radiotherapy
• Gross examination showed the tumor to be 10 × 8 × 15 cm with gelatinous brownish appearance

In September of 2014, Michael returns for follow up and his CT scan shows a 4 cm posterior mediastinal mass, and a 6 cm perinephric mass suspicious for metastatic disease. He initiates treatment with anthracycline and ifosfamide chemotherapy (6 cycles) for recurrent disease and shows a partial response.

• In May of 2015, he returns for follow up with intermittent chest and lower back pain; CT scan is consistent with progression of the mediastinal and perinephric masses, and bone scan shows new lesions occurring in the L2 and L3 lumbar vertebrae
• At recurrence, liver and renal function and CBC are within normal limits, and his ECOG performance status is 1
• He received treatment with trabectedin (1.5 mg/m2 24-hr infusion given every 3 week)
• At the 2nd cycle he develops febrile neutropenia (ANC< 500 cells/mm3) requiring hospitalization
• The oncologist reduces his trabectedin dose to 1.2 mg/m2; he continues therapy
• Within 1 week, he shows clinical improvement and CT scan shows slight improvement