Myxoid Liposarcoma
Definition
- Fatty neoplasm characterized by myxoid stroma, signet ring lipoblasts, regular small round cells and/or a prominent arborizing vascular pattern
Alternate/historical terms
- Round cell liposarcoma (for cellular cases)
Diagnostic Criteria
- Various patterns composed of histologic features described below, may be mixed
- Classical paucicellular pattern
- Predominently myxoid
- Scant cellularity
- Arborizing vascularity
- May lack lipoblasts
- Pulmonary edema-like
- Numerous microcysts
- May lack lipoblasts
- Sheets of lipoblasts
- Large fat cells with admixed lipoblasts
- No pleomorphic nuclei
- Cellular
- Sheets of back to back uniform round cells
- Must lack pleomorphism (see Pleomorphic Myxoid Liposarcoma below)
- Must be at least 25% cellular for this designation
- Pure cellular tumors may lack myxoid areas
- Must have at least focal lipoblasts
- Associated with significant metastatic potential
- Classical paucicellular pattern
- Histologic features seen in various patterns described above
- Myxoid, paucicellular stroma
- Arborizing, plexiform capillary network
- Chicken wire appearance
- Thin-walled vessels
- May be compressed and obscured in some non-myxoid patterns
- Signet ring lipoblasts
- Smaller than adult fat cells
- Usually single, clear fat vacuole
- Crescent or scalloped nuclei
- Uniform round cells
- Do not contain fat vacuoles
- Small uniform nuclei with granular chromatin and prominent nucleoli
- May be larger than cells in paucicellular areas
- May occasionally be spindled
- Microcysts
- Contain granular eosinophilic material
- Occasionally large and irregular
- Hypocellular areas around small to medium size arteries and veins
- All types lack pleomorphic cells
- Exception: may be seen in rare recurrences
- Features seen in rare cases
- Cords of cells with myxoid or hyalinized stroma
- Dedifferentiation as in usual dedifferentiated liposarcoma
- Non-fatty differentiation
- Cartilage or bone
- Smooth or skeletal muscle
- Pleomorphic myxoid liposarcoma has been reported in young patients
(Alaggio)
- 12 of 82 liposarcomas age 22 and under
- Typical myxoid pattern merging with hypercellular foci with marked pleomorphism and increased, atypical mitotic figures
- 70% mortality within 36 months
- Lacks CHOP translocations of usual myxoid type
- Not clear if this should be considered a variant of myxoid type, pleomorphic type, a mixed type, or a separate type
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting: August 4, 2007
Last update: May 8, 2011
