Soft tissue
Adipose tissue
Liposarcoma

Author: Vijay Shankar, M.D. (see Authors page)

Revised: 8 August 2016, last major update August 2012

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed Search: Liposarcoma [title] soft tissue

See also: Discussion in breast-malignant, heart, liver-tumor, oral cavity, pleura and testis chapters
Definition / General
  • Most common soft tissue sarcoma of adults (20%)
Epidemiology
  • Age 40+ years
  • Most cases in children are actually lipoblastoma or giant cell fibroblastoma
  • Rarely associated with multiple benign lipomas
Sites
  • Deep soft tissue (thigh, retroperitoneum, popliteal fossa)
  • Mediastinum is uncommon (Am J Surg Pathol 2007;31:1868)
  • Head and neck cases are often initially misdiagnosed, 53% recur (Head Neck 2009;31:28)
  • Usually NOT superficial, NOT intramuscular, NOT in neck
Prognosis and Treatment
  • Tumor size and histologic classification are important prognostic factors
  • Surgery still remains the mainstay of treatment and the only approach offering the potential of cure
  • Postoperative radiation reduces recurrence rate
  • 10 year local recurrence-free and metastasis-free survival in low-grade group is 87% and 95%, and in high-grade group is 75% and 61% (Cancer 2008;113:1649)
Clinical Images

Images hosted on PathOut servers:

MRI, right thigh (left two) and thigh x-ray (right), courtesy of Mark R. Wick, M.D.

Gross Description
  • Large, well circumscribed but not encapsulated
  • Mimics myxoma, lipoma and cerebral convolutions
Gross Images

Images hosted on PathOut servers:

Lipoblastic type, courtesy of Mark R. Wick, M.D.

Paratesticular (left) and well differentiated, thigh (right), courtesy of Mark R. Wick, M.D.

Micro Description
  • Per WHO (2002), composed of three subtypes:
    • 1. Well-differentiated and dedifferentiated liposarcoma (WDLPS / DDLPS)
    • 2. Myxoid and round cell liposarcoma (MLS and RCL)
    • 3. Pleomorphic liposarcoma (PLS)
  • Lipoblasts are relatively specific, resemble fetal fat cells, and are somewhat smaller than mature adipocytes
  • Lipoblasts have round, sharply demarcated cytoplasmic lipid (clear) vacuoles which scallop the nucleus and are smaller than vacuoles of mature adipocytes; spikes of chromatin may project between the vacuoles; may resemble signet ring cells or have central nuclei with small indentations by multiple fat vacuoles
Micro Images

Images hosted on PathOut servers:

Lipoblastic type (left three) and lipoma-like (right)
Courtesy of Mark R. Wick, M.D.

Positive Stains
Electron Microscopy Description
  • Lipoblasts resemble brown fat cells; are multivacuolated with lipid droplets, micropinocytotic vesicles, glycogen, external lamina, intermediate filaments, Golgi, rough and smooth endoplasmic reticulum, mitochondria
  • Lipoblasts frequently are close to capillaries and pericytes
  • Also lipid-free, poorly differentiated mesenchymal cells (Am J Clin Pathol 1986;85:649)
Differential Diagnosis
  • Clear cell melanoma: strong S100+, HMB45+
  • Fat necrosis: histiocytes are often circumferential around lipid droplets, associated with trauma, have central nucleus which is not deformed
  • Infiltration of fat by nonfatty tumors: fat cells are normal size and at periphery of lesion
  • Inflammatory lipoma
  • Intramuscular myxoma
  • Lipoblastoma / lipoblastomatosis
  • Lipogranuloma
  • Localized lipoatrophy: insulin injection sites
  • Metastatic signet ring cell carcinoma: infiltrative, cytokeratin+, mucin+
  • Pleomorphic / spindle cell lipoma
  • Silicon granuloma (image)