Adipocytic tumours

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Adipocytic tumours fall into the grouping soft tissue lesions and includes things that are very common (e.g. lipoma) and everything from benign to malignant.

Overview

This grouping includes a number of tumours, which can be divided based on their behaviour into benign, intermediate and malignant.

Benign

Benign adipocytic tumours:[1]

  • Lipoma.
  • Angiolipoma.
  • Myolipoma.
  • Pleomorphic lipoma.
  • Lipomatosis.
  • Lipomatosis of nerve.
  • Lipoblastoma.
  • Extrarenal angiomyolipoma.
  • Extra-adrenal myelolipoma.
  • Hibernoma.

Intermediate

Intermediate adipocytic tumours:[1]

  • Atypical lipomatous tumour.

Malignant

Malignant adipocytic tumours:[1]

  • Dedifferentiated liposarcoma.
  • Myxoid liposarcoma.
  • Pleomorphic liposarcoma.
  • Mixed-type liposarcoma.
  • Liposarcoma NOS.

Detail section

Normal mature fat

Microscopic

Features:

  • Adipocytes of approximately equal size.
  • Not vascular.
  • No nuclear hyperchromasia.

Notes:

  • May have nuclear pseudoinclusions (Lockhern cell).[2]
    • There is some suggestion this is not benign.[3]

Lipoma

General

Microscopic

Features:

  • Collection of mature adipocytes.
    • Variation of size may be seen -- should prompt a search for lipoblasts.[4]

Notes:

  • Microscopically not definitely distinguishable from mature clump of fat.
    • The lesion must be labeled lipoma to be signed-out as such.

Pleomorphic lipoma

General

  • Rare.
  • May mimic a malignancy.[5]

Microscopic

Features:

  • Multinucleated cells - "floret cells".
    • Very ugly looking cells.
  • Fibrous septa.

Image: Floret cells in a pleomorphic lipoma (pathconsultddx.com).[6]

Notes:

  • May overlap with spindle cell lipoma.[7]

Hibernoma

General

  • Consists of brown fat (present in the infants to generate heat).[8]
  • Benign.
  • Usually asymptomatic.[9]

Epidemiology

  • Young adults.

Gross

  • Well-circumscribed.
  • Lobulated and light-brown on sectioning.

Microscopic

Features:[10]

  • Large polygonal/oval cells:
    • Nucleus - central & small.[11]
      • Nucleoli typically prominent.[12]
    • Cytoplasm - multivacuolated, oval, eosinophilic, granular.

Image:

Atypical lipomatous tumour

  • AKA well-differentiated liposarcoma, abbreviated WDLPS.
  • Abbreviated ALT/WDLPS.

General

  • Atypical lipomatous tumour is a term used to save people with a (curable) peripheral liposarcoma from getting denied life insurance.

Microscopic

Features:[13]

  • Large adipocytes.
  • Atypical lipoblasts - focal, scattered:
    • Nuclear hyperchromasia.
    • +/-Multinucleated.

Liposarcoma

General

  • Most common malignant sarcoma in the retroperitoneum.
  • Not all (large) retroperitoneal adipocytic tumours are liposarcomas.

Microscopic

Features:

  • Lipoblasts - key feature.
    • Large sharply demarcated vacuole.
    • Nucleus:
      • Hyperchromatic (dark staining) nucleus.
      • Eccentric location.
      • Nuclear indentation.
  • Chicken wire-like vascular.
  • +/-Myxoid background.
  • Cell size variation.

Images:

Subtypes

There are several subtypes:[1]

  • Dedifferentiated liposarcoma.
  • Myxoid liposarcoma.
    • Round cell liposarcoma - a subtype of myxoid liposarcoma[14] that has a worse prognosis;[15] characterized by regions of high cellularity.
  • Mixed-type liposarcoma.
  • Pleomorphic liposarcoma.
  • Liposarcoma not otherwise specified (NOS).

IHC

  • IHC is of limited value.
  • S-100 +ve ~1/3 of the time.
  • Reticulin ???.

See also

References

  1. ↑ 1.0 1.1 1.2 1.3 Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 601. ISBN 978-0781765275.
  2. ↑ URL: http://journals.lww.com/amjdermatopathology/Citation/2004/12000/Original_Observation_to_Rediscovery__Nuclear.9.aspx. Accessed on: 18 April 2011.
  3. ↑ URL: http://www.pathconsultddx.com/pathCon/diagnosis?pii=S1559-8675%2806%2970574-5. Accessed on: 18 April 2011.
  4. ↑ Mentzel, T.; Fletcher, CD. (1995). "Lipomatous tumours of soft tissues: an update.". Virchows Arch 427 (4): 353-63. PMID 8548119.
  5. ↑ Persichetti, P.; Di Lella, F.; Marangi, GF.; Cagli, B.; Simone, P.; Tenna, S.; Rabitri, C.; Cassandro, R. et al. "Pleomorphic lipoma: a definite histopathological entity.". Anticancer Res 24 (5B): 3157-9. PMID 15510605.
  6. ↑ URL: http://www.pathconsultddx.com/pathCon/diagnosis?pii=S1559-8675%2806%2970321-7. Accessed on: 4 December 2010.
  7. ↑ URL: http://surgpathcriteria.stanford.edu/softfat/spindle_cell_lipoma/. Accessed on: 4 December 2010.
  8. ↑ Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 605. ISBN 978-0781765275.
  9. ↑ Ahmed SA, Schuller I (December 2008). "Pediatric hibernoma: a case review". J. Pediatr. Hematol. Oncol. 30 (12): 900–1. doi:10.1097/MPH.0b013e318184e6dd. PMID 19131775.
  10. ↑ Chen DY, Wang CM, Chan HL (March 1998). "Hibernoma. Case report and literature review". Dermatol Surg 24 (3): 393–5. PMID 9537018.
  11. ↑ http://www.pathconsultddx.com/pathCon/diagnosis?pii=S1559-8675(06)70271-6
  12. ↑ http://surgpathcriteria.stanford.edu/softfat/hibernoma/
  13. ↑ Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 605. ISBN 978-0781765275.
  14. ↑ Smith, TA.; Easley, KA.; Goldblum, JR. (Feb 1996). "Myxoid/round cell liposarcoma of the extremities. A clinicopathologic study of 29 cases with particular attention to extent of round cell liposarcoma.". Am J Surg Pathol 20 (2): 171-80. PMID 8554106.
  15. ↑ Conyers, R.; Young, S.; Thomas, DM. (2011). "Liposarcoma: molecular genetics and therapeutics.". Sarcoma 2011: 483154. doi:10.1155/2011/483154. PMID 21253554.
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