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Lipoblastoma / Lipoblastomatosis

Definition

  • Tumor of composed of immature fat cells admixed with mature fat

Diagnostic Criteria

  • Lipoblastoma is a solitary, circumscribed subcutaneous tumor
  • Lipoblastomatosis is a diffuse infiltrative tumor, usually deep
  • Very rarely presents over age 20 years
    • Usually presents under age 3
  • Lobular pattern
    • Separated by connective tissue septa
    • Septa rarely predominate
  • Immature fat cells admixed with mature fat
    • Variable appearances of immature cells
      • Small stellate or round immature mesenchymal cells, without fat vacuoles
      • Prominent single vacuole - signet ring
      • Multiple vacuoles resembling brown fat
    • Variable ratios of cell types
      • Maturity may vary between and within cases
      • May appear to mature on subsequent biopsies
      • Occasionally predominantly mature fat, especially in recurrences
      • Mature fat tends to predominate in center of lobules
    • Mitotic figures rare, none atypical
  • Richly vascular myxoid matrix
    • More prominent in immature areas
    • Plexiform vascular pattern if myxoid matrix is abundant
  • Occasional features
    • Hibernoma-like component with granular eosinophilic cytoplasm
    • Entrapped muscle fibers
      • Usually atrophic
    • Extramedullary hematopoeisis
  • Recognition of 18q11-13 abnormalities may expand the clinical and morpohologic spectrum of lipoblastoma / lipoblastomatosis
    • Lipoma-like lesions composed virtually entirely of mature adipose tissue
    • Atypical lipoma-like lesions with focal atypia
    • Hibernoma-like lesions with granular eosinophilic cytoplasm
    • Histologically typical lesions in slightly older patients
      • Reported in 23-24 year olds

Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting : July 29, 2007
Updates: February 9, 2009, May 25, 2009

Supplemental studies

Immunohistology

  • S100 labels fat cells but is seldom of diagnostic utility
  • One report of 100% CD34 reactivity in tumor cells (Coffin)
    • Not described or illustrated

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 Study

  • Nearly all cases have demonstrable abnormalities of 8q(11-13) or polysomy 8
    • Results in overexpression of PLAG1 gene
    • Demonstrable by FISH for PLAG1 or cytogenetics
    • FISH shows all cell types to be involved
      • Lipoblasts, mature adipocytes
      • Primitive mesenchymal cells and fibroblast-like cells

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

    Lipoma Lipoblastoma / Lipoblastomatosis
    Lacks primitive mesenchymal cells and lipoblasts Primitive mesenchymal cells and lipoblasts virtually always at least focally present
    Unusual on extremities Frequent on extremities
    Various chromosomal abnormalites but not involving 18q11-13 18q11-13 abnormalities
    Occasional lobules of lipoblastomatosis may be virtually indistinguishable

    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)

    Lipoblastoma Hibernoma
    Restricted to children at presentation Rare in children
    Immature cells and lipoblasts Microvesicular brown fat
    18q11-13 abnormalities 11q13 abnormalities

    Lipoblastoma Chondroid Lipoma
    Uniform population of lipoblasts Variable size of vacuolated cells
    No chondroid matrix Chondroid matrix
    Restricted to children Age range 14-75
    Deletions of 8q(11-13) t(11;16)

    Lipoblastoma Fat Necrosis
    At least focal vascular myxoid stroma Lacks vascular myxoid stroma
    Immature fat cells with vacuoles Foamy cytoplasm, few vacuoles
    Uniform pattern Variable pattern from normal fat to necrotic fat to histiocytes

    Lipoblastoma with Extramedullary Hematopoiesis Myelolipoma
    Immature fat cells present No immature fat cells
    Areas with vascular myxoid stroma Lacks vascular myxoid stroma
    Usually under age 10, virtually always under 20 Usually over age 40

    Lipoblastoma / Lipoblastomatosis Lipofibromatosis
    Septa infrequently cellular Prominently cellular septa
    Usually immature fat mixed with mature Mature fat
    Fat cells may have multiple vacuoles Single fat vacuoles

    Lipoblastomatosis Infantile Fibromatosis
    At least focal plexiform capillaries No plexiform capillaries
    Contains lipoblasts Mature fat cells only
    Lobular pattern Infiltrative pattern

    Clinical

    • Usually under age 3
      • Presentation over age 20 is very rare
    • Site
      • May involve both trunk and extremities
      • Most are circumscribed, subcutaneous
      • Less commonly deep in skeletal muscle, retroperitoneum, mesentery
    • Behavior
      • Superficial lesions rarely recur
      • Deep lesions repeatedly recur
      • No metastases
    • One report of associated nervous system disorders in 17% of patients (Coffin)

    Lists

    Lipogenic tumors

    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
    • Rubin BP, Dal Cin P. The genetics of lipomatous tumors. Semin Diagn Pathol. 2001 Nov;18(4):286-93.
    • Mentzel T, Calonje E, Fletcher CD. Lipoblastoma and lipoblastomatosis: a clinicopathological study of 14 cases. Histopathology. 1993 Dec;23(6):527-33.
    • Collins MH, Chatten J. Lipoblastoma/lipoblastomatosis: a clinicopathologic study of 25 tumors. Am J Surg Pathol. 1997 Oct;21(10):1131-7.
    • Hicks J, Dilley A, Patel D, Barrish J, Zhu SH, Brandt M. Lipoblastoma and lipoblastomatosis in infancy and childhood: histopathologic, ultrastructural, and cytogenetic features. Ultrastruct Pathol. 2001 Jul-Aug;25(4):321-33.
    • Jung SM, Chang PY, Luo CC, Huang CS, Lai JY, Hsueh C. Lipoblastoma/lipoblastomatosis: a clinicopathologic study of 16 cases in Taiwan. Pediatr Surg Int. 2005 Oct;21(10):809-12.
    • de Saint Aubain Somerhausen N, Coindre JM, Debiec-Rychter M, Delplace J, Sciot R. Lipoblastoma in adolescents and young adults: report of six cases with FISH analysis. Histopathology. 2008 Feb;52(3):294-8.
    • Brandal P, Bjerkehagen B, Heim S. Rearrangement of chromosomal region 8q11-13 in lipomatous tumours: correlation with lipoblastoma morphology. J Pathol. 2006 Feb;208(3):388-94.
    • Gisselsson D, Hibbard MK, Dal Cin P, Sciot R, Hsi BL, Kozakewich HP, Fletcher JA. PLAG1 alterations in lipoblastoma: involvement in varied mesenchymal cell types and evidence for alternative oncogenic mechanisms. Am J Pathol. 2001 Sep;159(3):955-62.
    • Coffin CM, Lowichik A, Putnam A. Lipoblastoma (LPB): A Clinicopathologic and Immunohistochemical Analysis of 59 Cases. Am J Surg Pathol. 2009 Nov;33(11):1705-12
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