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]

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]

IHC

  • S100 +ve.

Lipoblastoma

General

  • Rare paediatric tumour.[4]

Usual presentation:[4]

  • Painless neck mass.

Microscopic

Features:

  • Nests of cells in the dermis with abundant pale cytoplasm - vaguely resemble adipocytes.
    • Smaller than mature adipocytes.

DDx:

Images:

Lipoma

General

Microscopic

Features:

  • Collection of mature adipocytes.
    • Variation of size may be seen -- should prompt a search for lipoblasts.[6]

Notes:

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

DDx:

  • Liposarcoma - increased number of blood vessels,[7] esp. chickenwire-like vessels, fibrous septae.
  • Benign adipose tissue.

Images:

Variants

Angiolipoma

Microscopic:

  • Numerous blood vessels present.
  • +/-Microthrombi.

DDx:

Myolipoma

General:

  • May mimic a sarcoma radiologically.[9]
  • Extremely rare.[10]
  • Usually large ~ 16 cm.[11]

Microscopic:[10]

  • Mature adipose tissue.
  • Benign smooth muscle - usually ~ 2x amount of fat.

Note:

  • If skeletal muscle is present consider intramuscular lipoma.[12]

IHC:[10]

  • Actin +ve.
  • Desmin +ve.

Images:

Sign out

SUBCUTANEOUS TISSUE ("LIPOMA"), LEFT AXILLA, EXCISION: 
- MATURE ADIPOSE TISSUE CONSISTENT WITH LIPOMA.

LESION ("LIPOMA"), SPERMATIC CORD (LATERALITY NOT SPECIFIED), EXCISION: 
- MATURE ADIPOSE TISSUE CONSISTENT WITH LIPOMA.

Colonic lipoma (clinically suspected)

B. SIGMOID COLON AT 55 CM, BIOPSY:
- COLORECTAL-TYPE MUCOSA WITHIN NORMAL LIMITS WITH A SMALL AMOUNT OF SUBMUCOSAL
  ADIPOSE TISSUE; COMPATIBLE WITH CLINICAL IMPRESSION OF LIPOMA.

Mirco

The sections show mature adipocytes. There is no increase in vascularity. No thick fibrous septa are present.

Pleomorphic lipoma

General

  • Rare.
  • May mimic a malignancy.[14]
  • Male > female.[15]

Gross

  • Classically shoulder and neck region in adults.[16]

DDx - shoulder lesions:

Microscopic

Features:

  • Multinucleated cells - "floret cells" - key feature.
    • Solid eosinophilic cytoplasm.
    • Peripheral nuclei - impart a knobby border to the cells.
  • Fibrous septa.

Notes:

Images:

DDx:

IHC

  • AR +ve - ~95% in men, ~85% in women.[15]

Spindle cell lipoma

General

  • Rare.
  • Predominantly men.[10]

Note:

  • Spindle cell lipoma may immunohistochemically and histomorphologically overlap with mammary-type myofibroblastoma[18] - see: mammary myofibroblastoma.

Microscopic

Features:[10]

  • Aligned bland spindled cells adjacent to fat.
  • Rope-like collagen bundles - key feature.
    • May be described as "shreaded wheat".
  • +/-Myxoid component.
  • +/-Staghorn-like vessels.

Notes:

DDx:

Image

www:

IHC

  • CD34 +ve.[20]
  • Desmin +ve.
  • S100 -ve. (???)

Hibernoma

Main article: Hibernoma

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:[21]

  • 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.

Notes:

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.

DDx:

Images:

Subtypes

Main subtypes:[1]

  • Dedifferentiated liposarcoma.
  • Myxoid liposarcoma.
    • Round cell liposarcoma - a subtype of myxoid liposarcoma[22] that has a worse prognosis;[23] characterized by regions of high cellularity.
  • Mixed-type liposarcoma.
  • Pleomorphic liposarcoma.
  • Liposarcoma not otherwise specified (NOS).

Additional reported type:

  • Spindle cell liposarcoma.[19]
Myxoid liposarcoma
  • AKA myxoid/round cell liposarcoma.
  • AKA round cell liposarcoma.
Gross

Location:[24]

  • 90% in lower limb.
  • 81% deep.
Microscopic

Features:

  • Chickenwire-type blood vessels.
  • Clear spaces.
  • Adipocytes - may be rare.

DDx:

Images:

Molecular

Typically has a translocation:

Dedifferentiated liposarcoma
  • Has an undifferentiated component that, if seen alone, would be diagnosed as pleomorphic undifferentiated sarcoma.
  • The diagnosis depends on the presence of the differentiated component of the tumour, i.e. the presence of lipoblasts.

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. ↑ 4.0 4.1 Pham, NS.; Poirier, B.; Fuller, SC.; Dublin, AB.; Tollefson, TT. (Jul 2010). "Pediatric lipoblastoma in the head and neck: a systematic review of 48 reported cases.". Int J Pediatr Otorhinolaryngol 74 (7): 723-8. doi:10.1016/j.ijporl.2010.04.010. PMID 20472310.
  5. ↑ Nagano, A.; Ohno, T.; Nishimoto, Y.; Hirose, Y.; Miyake, S.; Shimizu, K. (2011). "Lipoblastoma mimicking myxoid liposarcoma: a clinical report and literature review.". Tohoku J Exp Med 223 (1): 75-8. PMID 21212605.
  6. ↑ Mentzel, T.; Fletcher, CD. (1995). "Lipomatous tumours of soft tissues: an update.". Virchows Arch 427 (4): 353-63. PMID 8548119.
  7. ↑ Yang, YJ.; Damron, TA.; Cohen, H.; Hojnowski, L. (Oct 2001). "Distinction of well-differentiated liposarcoma from lipoma in two patients with multiple well-differentiated fatty masses.". Skeletal Radiol 30 (10): 584-9. doi:10.1007/s002560100395. PMID 11685482.
  8. ↑ Friedberg, MK.; Chang, IL.; Silverman, NH.; Ramamoorthy, C.; Chan, FP. (May 2006). "Images in cardiovascular medicine. Near sudden death from cardiac lipoma in an adolescent.". Circulation 113 (21): e778-9. doi:10.1161/CIRCULATIONAHA.105.589630. PMID 16735681. http://circ.ahajournals.org/content/113/21/e778.full.
  9. ↑ URL: http://www.webmedcentral.com/article_view/1878. Accessed on: 14 March 2013.
  10. ↑ 10.0 10.1 10.2 10.3 10.4 Murphey, MD.; Carroll, JF.; Flemming, DJ.; Pope, TL.; Gannon, FH.; Kransdorf, MJ.. "From the archives of the AFIP: benign musculoskeletal lipomatous lesions.". Radiographics 24 (5): 1433-66. doi:10.1148/rg.245045120. PMID 15371618. http://radiographics.rsna.org/content/24/5/1433.long. Cite error: Invalid <ref> tag; name "pmid15371618" defined multiple times with different content
  11. ↑ Meis, JM.; Enzinger, FM. (Feb 1991). "Myolipoma of soft tissue.". Am J Surg Pathol 15 (2): 121-5. PMID 1703396.
  12. ↑ URL: http://surgpathcriteria.stanford.edu/softfat/lipoma/intramuscular_lipoma.html. Accessed on: 14 March 2013.
  13. ↑ Lee, YS.; Park, SE.; Lee, JU.; Choi, ES.. "MRI of a subcutaneous myolipoma in the ankle: a case report.". Korean J Radiol 12 (5): 641-5. doi:10.3348/kjr.2011.12.5.641. PMC 3168809. PMID 21927569. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3168809/.
  14. ↑ 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.
  15. ↑ 15.0 15.1 Syed, S.; Martin, AM.; Haupt, H.; Podolski, V.; Brooks, JJ. (Jan 2008). "Frequent detection of androgen receptors in spindle cell lipomas: an explanation for this lesion's male predominance?". Arch Pathol Lab Med 132 (1): 81-3. doi:10.1043/1543-2165(2008)132[81:FDOARI]2.0.CO;2. PMID 18181679.
  16. ↑ URL: http://www.webpathology.com/image.asp?n=2&Case=435. Accessed on: 3 October 2011.
  17. ↑ 17.0 17.1 URL: http://surgpathcriteria.stanford.edu/softfat/spindle_cell_lipoma/. Accessed on: 4 December 2010.
  18. ↑ McMenamin, ME.; Fletcher, CD. (Aug 2001). "Mammary-type myofibroblastoma of soft tissue: a tumor closely related to spindle cell lipoma.". Am J Surg Pathol 25 (8): 1022-9. PMID 11474286.
  19. ↑ 19.0 19.1 Dei Tos, AP.; Mentzel, T.; Newman, PL.; Fletcher, CD. (Sep 1994). "Spindle cell liposarcoma, a hitherto unrecognized variant of liposarcoma. Analysis of six cases.". Am J Surg Pathol 18 (9): 913-21. PMID 8067512.
  20. ↑ Wood, L.; Fountaine, TJ.; Rosamilia, L.; Helm, KF.; Clarke, LE. (Dec 2010). "Cutaneous CD34+ spindle cell neoplasms: Histopathologic features distinguish spindle cell lipoma, solitary fibrous tumor, and dermatofibrosarcoma protuberans.". Am J Dermatopathol 32 (8): 764-8. doi:10.1097/DAD.0b013e3181d0c587. PMID 20559119.
  21. ↑ 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.
  22. ↑ 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.
  23. ↑ Conyers, R.; Young, S.; Thomas, DM. (2011). "Liposarcoma: molecular genetics and therapeutics.". Sarcoma 2011: 483154. doi:10.1155/2011/483154. PMID 21253554.
  24. ↑ Moreau, LC.; Turcotte, R.; Ferguson, P.; Wunder, J.; Clarkson, P.; Masri, B.; Isler, M.; Dion, N. et al. (Apr 2012). "Myxoid\Round Cell Liposarcoma (MRCLS) Revisited: An Analysis of 418 Primarily Managed Cases.". Ann Surg Oncol 19 (4): 1081-1088. doi:10.1245/s10434-011-2127-z. PMID 22052112.
  25. ↑ Knight, JC.; Renwick, PJ.; Dal Cin, P.; Van den Berghe, H.; Fletcher, CD. (Jan 1995). "Translocation t(12;16)(q13;p11) in myxoid liposarcoma and round cell liposarcoma: molecular and cytogenetic analysis.". Cancer Res 55 (1): 24-7. PMID 7805034.
  26. ↑ Suzuki, K.; Matsui, Y.; Endo, K.; Kubo, T.; Hasegawa, T.; Kimura, T.; Ohtani, O.; Yasui, N. (Nov 2010). "Myxoid liposarcoma with EWS-CHOP type 1 fusion gene.". Anticancer Res 30 (11): 4679-83. PMID 21115923.
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