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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
  • 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

Supplemental studies

Immunohistology

  • S100 stains mature fat cells and lipoblasts but is rarely of diagnostic use
  • CD34 negative or stains rare small cells
  • MDM2 and CDK4 generally negative
Immunohistochemistry of lipomatous tumors
  MDM2 CDK4 p16
Atypical lipomatous tumor 45-100% 84-92% 78-97%
Dedifferentiated liposarcoma 55-95 90-100 90
Myxoid / round cell liposarcoma 0-4 0-4 0
Pleomorphic liposarcoma 0 0 0
Lipoma 0-4 0-2 0
Spindle cell and pleomorphic lipoma 0-25 0-6 20
Angiomyolipoma 0 0  
Hibernoma 0 0 positive, variable
Lipoblastoma 0 (1 case) 0 (1 case) positive (1 case)

Genetic analysis

  • FUS/CHOP t(12;16)(q13;p11) in 90% of cases
  • EWS/CHOP t(12;22)(q13;q12) in remainder
FISH/PCR of lipomatous tumors
  MDM2 FISH MDM2 QPCR CDK4 FISH CDK4 QPCR
Atypical lipomatous tumor 90-100% 72-100% 75-100% 69-100%
Dedifferentiated liposarcoma 100% 100% 100% 100%
Myxoid liposarcoma 20%      
Spindle cell / pleomorphic lipoma Negative Negative Negative Negative
Angiolipoma Negative      
Lipoma, NOS Negative Negative Negative Negative
Sarcomas 0-40% 0% 0% 0%
  • Spindle cell / pleomorphic lipoma showed 89% chromosome 12 polysomy
  • Differential Diagnosis

    Myxoid Liposarcoma Lipoblastoma / Lipoblastomatosis
    Maturation if present, occurs towards periphery Maturation if present, occurs towards center of lobules
    Rare <20, very rare <10 Very rare >20, rare >10
    May have hypercellular areas Uniformly hypocellular
    Virtually always deep May be superficial or deep
    t(12;16) or t(12;22) Abnormalities involving 8q(11-13)

    Myxoid Liposarcoma Spindle Cell Lipoma with Myxoid Stroma
    Infrequent prominent spindle cell component Prominent spindle cell component
    Prominent "chicken wire" vascular pattern Lacks "chicken wire" vascular pattern
    No dense collagen bundles Dense collagen bundles
    Very rare in subcutis or dermis Usually in subcutis or dermis
    CD34 negative or scattered small cells CD34 widely positive
    t(12;16) or t(12;22) Frequent abnormalities of chromosomes 13 or 16

    Myxoid Liposarcoma Atypical Lipomatous Tumor
    No large atypical nuclei Large atypical nuclei present
    Prominent "chicken wire" vascular pattern Lacks "chicken wire" vascular pattern
    Rare as a primary lesion in retroperitoneum Frequently occurs in retroperitoneum
    MDM2 and CDK4 4% by immunohistology but 1/5 MDM2 by FISH MDM2 and CDK4 most positive

    Myxoid Liposarcoma Chondroid Lipoma
    No chondroid matrix Chondroid matrix
    Prominent "chicken wire" vascular pattern Lacks "chicken wire" vascular pattern
    Cells more uniform Cells frequently variable in size

    Myxoid Liposarcoma Myxolipoma / Angiomyxolipoma
    Prominent "chicken wire" vascular pattern Lacks "chicken wire" vascular pattern
    May have lipoblasts Lacks lipoblasts
    Very rare in subcutis or dermis Usually in subcutis or dermis
    CD34 negative or scattered small cells CD34 widely positive in myxoid areas
    t(12;16) or t(12;22) t(7;13) or t(8;12) reported

    Myxoid Liposarcoma Hibernoma with Myxoid Stroma
    Rarely superficial Frequently superficial
    Prominent "chicken wire" vascular pattern Lacks "chicken wire" vascular pattern
    t(12;16) or t(12;22) 11q13 rearrangement

    Myxoid Liposarcoma Aggressive Angiomyxoma
    Arborizing vessels Large, disorganized vessels
    Signet ring lipoblasts Lacks lipoblasts

    Myxoid Liposarcoma Intramuscular Myxoma
    Arborizing vascular pattern Hypovascular
    Lipoblasts present, usually signet ring type No lipoblasts
    More cellular Extremely paucicellular

    Myxoid Liposarcoma Juxta-articular Myxoma
    Lipoblasts present, usually signet ring type No lipoblasts
    Arborizing vascular pattern Hypovascular

    Myxoid Liposarcoma Myxofibrosarcoma
    Lipoblasts frequent No lipoblasts
    Vacuoles in lipoblasts are clear Vacuoles, if present, contain material similar to adjacent myxoid stroma
    Lacks pleomorphic cells At least focally pleomorphic
    Rare in subcutis Frequent in subcutis
    t(12;16) or t(12;22) No consistent abnormalities

    Myxoid Liposarcoma Extraskeletal Myxoid Chondrosarcoma
    Lipoblasts frequent No lipoblasts
    Arborizing vasculature pattern Lacks arborizing pattern
    Cords of cells unusual Usually clusters and cords of cells
    t(12;16) or t(12;22) t(9;22) or t(9;17)

    Pure Cellular Myxoid Liposarcoma Small Round Blue Cell Tumors (Various)
    Lipoblasts frequent No lipoblasts
    Lacks significant pleomorphism May be pleomorphic
    No immunologic evidence of differentiation Specific markers may be positive
    t(12;16) or t(12;22) Specific translocations may be present

    Clinical

    • Rare <20 years, very rare <10 years of age
      • Myxoid liposarcoma is the most common type under age 20
      • Good prognosis, with similar behavior to adults
    • Most common in thigh
      • Other sites include popliteal, groin, buttock
      • Rare in retroperitoneum
        • May metastasize to this site
        • Apparent primary retroperitoneal tumors appear to be atypical lipomatous tumors genetically (de Vreeze)
      • Very rare in subcutis
    • Prognosis
      • Low cellularity tumors may metastasize, but only rarely
      • Cellular (25% of area) tumors frequently metasasize
        • Rate of metastasis is related to proportion of tumor that is cellular
        • Metastases frequently delayed
          • Median time 5-6 years
          • Most frequent sites are retroperitoneum, mediastinum, spine

    Grading / Staging / Report

    Grading is determined by cellularity and designated paucicellular and cellular

    • Cellular
      • Sheets of back to back uniform cells
        • Cells may be larger than in paucicellular areas
        • May have more granular chromatin and prominent nucleoli
      • Degree of cellularity must be specified
        • 25% cellular defined as cellular myxoid liposarcoma
          • Associated with significant metastatic potential

    French Federation of Cancer Centers System grading scheme for adult sarcomas

    • Tumor differentiation score = 2 if paucicellular, 3 if cellular
    • Mitotic index
      • Score 1 0-9 mitoses per 10 hpf (0.1744 sq mm)
      • Score 2 10-19 mitoses per 10 hpf
      • Score 3 >19 mitoses per 10 hpf
    • Tumor cell necrosis
      • Score 0 No necrosis on any slide (one slide per 2 cm tumor diameter)
      • Score 1 <50% of tumor is necrotic on slides examined
      • Score 2 >50% of tumor is necrotic on slides examined
    • Final Grade (add the three scores above)
      • Grade 1 Sum of scores = 2 or 3
      • Grade 2 Sum of scores = 4 or 5
      • Grade 3 Sum of scores = 6 or more

    Use TNM Staging

    The surgical pathology report should contain or address the following:

    • Location
    • Type of resection or biopsy
    • Histologic diagnosis
    • Managerial category III (Local recurrence common; Metastasis occurs)
    • Extent of tumor cell necrosis
    • Grade
      • Paucicellular vs. cellular
        • Give percent cellular
    • Stage
    • Size
    • Depth (dermis, subcutis, below fascia, body cavity)
    • Margins
      • Involved
      • Not involved
        • If under 2 cm give all such distances and sites
        • If over 2 cm give minimum distance and site
    • Results of supplementary studies if performed
    • Relationship to other specimens from the same patient

     

     

    Lists

    Lipogenic tumors

    Soft tissue lesions that frequently are prominently myxoid

    Bibliography

    • Kempson RL, Fletcher CDM, Evans HL, Henrickson MR, Sibley RS. Tumors of the Soft Tissues, Atlas of Tumor Pathology, AFIP Third Series, Fascicle 30, 2001
    • Fletcher CDM, Unni KK, Mertens F. Pathology and Genetics of Tumours of Soft Tissue and Bone, World Health Organization Classification of Tumours 2002
    • Weiss SW, Goldblum JR. Enzinger and Weiss's Soft Tissue Tumors, 4th edition, 2001
    • Azumi N, Curtis J, Kempson RL, Hendrickson MR. Atypical and malignant neoplasms showing lipomatous differentiation. A study of 111 cases. Am J Surg Pathol. 1987 Mar;11(3):161-83.
    • Rubin BP, Dal Cin P. The genetics of lipomatous tumors. Semin Diagn Pathol. 2001 Nov;18(4):286-93.
    • Siebert JD, Williams RP, Pulitzer DR. Myxoid liposarcoma with cartilaginous differentiation. Mod Pathol. 1996 Mar;9(3):249-52.
    • Dijkhuizen T, Molenaar WM, Hoekstra HJ, Wiersema J, van den Berg E. Cytogenetic analysis of a case of myxoid liposarcoma with cartilaginous differentiation. Cancer Genet Cytogenet. 1996 Dec;92(2):141-3.
    • Shanks JH, Banerjee SS, Eyden BP. Focal rhabdomyosarcomatous differentiation in primary liposarcoma. J Clin Pathol. 1996 Sep;49(9):770-2.
    • Knight JC, Renwick PJ, Cin PD, Van den Berghe H, Fletcher CD. Translocation t(12;16)(q13;p11) in myxoid liposarcoma and round cell liposarcoma: molecular and cytogenetic analysis. Cancer Res. 1995 Jan 1;55(1):24-7.
    • Behranwala KA, Roy P, Giblin V, A'hern R, Fisher C, Thomas JM. Intra abdominal metastases from soft tissue sarcoma. J Surg Oncol. 2004 Sep 1;87(3):116-20.
    • Orvieto E, Furlanetto A, Laurino L, Del Tos AP. Myxoid and round cell liposarcoma: a spectrum of myxoid adipocytic neoplasia. Semin Diagn Pathol. 2001 Nov;18(4):267-73.
    • Binh MB, Sastre-Garau X, Guillou L, de Pinieux G, Terrier P, Lagace R, Aurias A,
      Hostein I, Coindre JM. MDM2 and CDK4 immunostainings are useful adjuncts in diagnosing
      well-differentiated and dedifferentiated liposarcoma subtypes: a comparative
      analysis of 559 soft tissue neoplasms with genetic data. Am J Surg Pathol. 2005 Oct;29(10):1340-7.
    • Alaggio R, Coffin CM, Weiss SW, Bridge JA, Issakov J, Oliveira AM, Folpe AL. Liposarcomas in young patients: a study of 82 cases occurring in patients younger than 22 years of age. Am J Surg Pathol. 2009 May;33(5):645-58.
    • de Vreeze RS, de Jong D, Tielen IH, Ruijter HJ, Nederlof PM, Haas RL, van Coevorden F. Primary retroperitoneal myxoid/round cell liposarcoma is a nonexisting disease: an immunohistochemical and molecular biological analysis. Mod Pathol. 2009 Feb;22(2):223-31.

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