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Atypical Lipomatous Tumor, Well-Differentiated Liposarcoma

DEFINITION AND PATHOGENESIS

  • Takes

IMPORTANCE

  • Most common liposarcoma in the elderly 
  •  

CLINICAL FEATURES

  • Slowly enlarging mass that may be present for yrs
  • Peak incidence in 6-7th decades
  • M=F
  • Extremities (75%) > retroperitoneum (20%)

RADIOLOGIC FEATURES

  • Depend  

GROSS PATHOLOGY

  • Yellow to ivory in color
  • Multilobular

HISTOLOGIC  AND MOLECULAR FEATURES

  • Mature fat, spindled cells, multivaculated lipoblasts
  • Subtypes (may overlap)
    • Lipoma-like
    • Sclerosing
      • Groin and retroperitoneum most commonly
      • Fibrotic trabeculae
        • ± sheets of collagen
          • Beware of bxs from these areas only
      • Few lipoblasts
    • Inflammatory
      • Lymphocytic infiltrates present
  • Areas of smooth muscle have been reported
    • Spermatic cord location
    • Mediastinal location
    • Retroperitoneal location
  • Cytology
  • Immunohistochemistry
    • MDM2 +
    • CDK4 +
  • Giant marker and ring chromosomes
    • Amplified sequences of 12q13-15 genes reported
      • MDM2
      • GLI
      • SAS
      • CDK4
      • HMGIC

DIFFERENTIAL CLINICOPATHOLOGIC DIAGNOSIS

  • Lipoma with fat necrosis
  • Spindle cell lipoma
    • Some reported + for MDM2 and CDK4
  • Pleomorphic lipoma
    • Some reported + for MDM2 and CDK4
  • Cellular angiolipoma

DISEASE COURSE AND TREATMENT

  • Wide
  • Retroperitoneal locations with extremely high LR
  • Dedifferentiation occurs as the natural hx

SPECIAL CONSIDERATION

  • Lipoleimyosarcoma

    • Well-differentiated liposarcoma with a smooth muscle component
    • Leiomyosarcomatous dedifferentiation heralds a higher grade sarcoma


REFERENCES

Arkun R, Memis A, Akalin T,                   : Liposarcoma of soft tissue: MRI findings with pathologic correlation. Skeletal Radiol. 1997;26:167-

Ehara S, Rosenberg AE, Kattapuram SV: Atypical lipomas, liposarcomas, and other fat containing sarcoma: CT analysis of the fat element. Clin Imaging. 1995;19:50-

Evans HL: Am J Surg Pathol. 1009 Aug;14(8):714-8.

Fernandez-Flores A, Juanes F: Value of cytological imprints in the diagnosis of atypical lipomatous tumor. Diagn Cytopathol. 2005 Jan;32(1):51-2.

Jelinek JS, Kransdorf MJ, Schmookler BM,               : Liposarcoma of the extremities: MR and CT findings in the histologic subtypes. Radiology. 1993;186:455-

Kraus MD, Guillou L, Fletcher CD: Well-differentiated inflammatory liposarcoma: an uncommon and easily overlooked variant of a common sarcoma. Am J Surg Pathol. 1997;21:518-

Lucas DR, Nascimento AG, Sanjay KSS,             : Well-differentiated liposarcoma: the Mayo Clinic experience with 58 cases. Am J Clin Pathol 1994;102:677-

Weiss SW, Rao VK: Well-differentiated liposarcoma (atypical lipoma) of deep soft tissue of the extremities, retroperitoneum and miscellaneous sites: a follow-up study of 92 cases with analysis of the incidence of "dedifferentiation." Am J Surg Pathol. 1992;16:1051-

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