Liposarcoma pathophysiology: Difference between revisions

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Frequently composed by [[adipocytes]] with different cell sizes, hyperchromasia and nuclear atypia.  [[Fibrous]] septa may be identified among [[adipocytes]], containing hyperchromatic [[stromal cells]].  Besides these two types of cells, mono or multivacuolated lipoblasts may also be identified.  These last are characterized by the presence of single (mono) or multiple (multi) peripheral cytoplasmic vacuoles that press on the hyperchromatic nucleus.<ref name="pmid10982304">{{cite journal| author=Dei Tos AP| title=Liposarcoma: new entities and evolving concepts. | journal=Ann Diagn Pathol | year= 2000 | volume= 4 | issue= 4 | pages= 252-66 | pmid=10982304 | doi=10.1053/adpa.2000.8133 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=10982304  }} </ref>
Frequently composed by [[adipocytes]] with different cell sizes, hyperchromasia and nuclear atypia.  [[Fibrous]] septa may be identified among [[adipocytes]], containing hyperchromatic [[stromal cells]].  Besides these two types of cells, mono or multivacuolated lipoblasts may also be identified.  These last are characterized by the presence of single (mono) or multiple (multi) peripheral cytoplasmic vacuoles that press on the hyperchromatic nucleus.<ref name="pmid10982304">{{cite journal| author=Dei Tos AP| title=Liposarcoma: new entities and evolving concepts. | journal=Ann Diagn Pathol | year= 2000 | volume= 4 | issue= 4 | pages= 252-66 | pmid=10982304 | doi=10.1053/adpa.2000.8133 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=10982304  }} </ref>


 
In general, adipocytic [[neoplasms]] are often identified by the presence of these lipoblasts, however, its presence is not synonym, nor are they identified in every liposarcoma.<ref name="pmid10982304">{{cite journal| author=Dei Tos AP| title=Liposarcoma: new entities and evolving concepts. | journal=Ann Diagn Pathol | year= 2000 | volume= 4 | issue= 4 | pages= 252-66 | pmid=10982304 | doi=10.1053/adpa.2000.8133 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=10982304  }} </ref>
In general, [[adipocytic]] [[neoplasms]] are often identified by the presence of these lipoblasts.<ref name="pmid10982304">{{cite journal| author=Dei Tos AP| title=Liposarcoma: new entities and evolving concepts. | journal=Ann Diagn Pathol | year= 2000 | volume= 4 | issue= 4 | pages= 252-66 | pmid=10982304 | doi=10.1053/adpa.2000.8133 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=10982304  }} </ref>




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However, it is important to emphasize that the mere presence of lipoblasts does not make (or is required for) a diagnosis of liposarcoma. As a matter of fact, there exist a number of entirely benign adipocytic lesions (eg, lipoblastoma, pleomorphic lipoma, chondroid lipoma) that may contain numerous lipoblasts. By contrast, the absence of lipoblasts within an adipocytic neoplasm fulfilling all the remaining diagnostic criteria for liposar- coma does not prevent such a diagnosis.
As a matter of fact, there exist a number of entirely benign adipocytic lesions (eg, lipoblastoma, pleomorphic lipoma, chondroid lipoma) that may contain numerous lipoblasts. By contrast, the absence of lipoblasts within an adipocytic neoplasm fulfilling all the remaining diagnostic criteria for liposar- coma does not prevent such a diagnosis.


Another morphologic variation that represents a potential diagnostic pitfall is the presence of a chronic inflammatory infiltrate to the extent that the adipocytic nature of the neoplasm can be obscured (Fig 5). The existence of examples of liposarcoma characterized by the presence of prominent mononuclear inflammatory infiltrates has been acknowledged since the publication of Stout’s5 classification of liposarcoma. Nonetheless, reports dealing specifically with this subtype have not been available until very recently.6,7 The inflammatory infiltrate is usually composed of polyphenotypic lympho- plasmacytic aggregates in which a B-cell phenotype tends to predominate. However, cases exist in which a T-cell population represents the main inflammatory component. Differential diagnosis includes nonadipo- cytic lesions such as inflammatory myofibroblastic tu- mor and Castleman’s disease. Careful as well as exten- sive sampling is mandatory to permit recognition of the adipocytic component that otherwise could be easily missed. The presence of bizarre multinucleate stromal cells represents a useful diagnostic clue.
Another morphologic variation that represents a potential diagnostic pitfall is the presence of a chronic inflammatory infiltrate to the extent that the adipocytic nature of the neoplasm can be obscured (Fig 5). The existence of examples of liposarcoma characterized by the presence of prominent mononuclear inflammatory infiltrates has been acknowledged since the publication of Stout’s5 classification of liposarcoma. Nonetheless, reports dealing specifically with this subtype have not been available until very recently.6,7 The inflammatory infiltrate is usually composed of polyphenotypic lympho- plasmacytic aggregates in which a B-cell phenotype tends to predominate. However, cases exist in which a T-cell population represents the main inflammatory component. Differential diagnosis includes nonadipo- cytic lesions such as inflammatory myofibroblastic tu- mor and Castleman’s disease. Careful as well as exten- sive sampling is mandatory to permit recognition of the adipocytic component that otherwise could be easily missed. The presence of bizarre multinucleate stromal cells represents a useful diagnostic clue.

Revision as of 15:57, 19 September 2014

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]

Overview

Pathogenesis

According to their class, each liposarcoma will have specific characteristics and pathogenesis:

Well Differentiated Liposarcoma

This type of liposarcoma occurs both at the limbs and retroperitoneum in equal frequency, and occasionally at the mediastinum and spermatic cord, representing about 45% of liposarcomas.[1]

According to the WHO classification described previously, well differentiated liposarcomas may be sub-classified into 3 types: sclerosing; adipocytic; and inflammatory.

Sclerosing Liposarcoma

Occurs most frequently at the retroperitoneum and paratesticular regions. The particular histological finding in this type of well differentiated liposarcoma is the identification of distinctive stromal cells distributed across the tissue, and associated with lipoblasts filled with multiple vacuoles. This association forms a collagenous background of fibrillary appearance. In certain cases the fibrous component of the neoplasm may occupy most of its mass.[1]

Adipocytic Liposarcoma

Frequently composed by adipocytes with different cell sizes, hyperchromasia and nuclear atypia. Fibrous septa may be identified among adipocytes, containing hyperchromatic stromal cells. Besides these two types of cells, mono or multivacuolated lipoblasts may also be identified. These last are characterized by the presence of single (mono) or multiple (multi) peripheral cytoplasmic vacuoles that press on the hyperchromatic nucleus.[1]

In general, adipocytic neoplasms are often identified by the presence of these lipoblasts, however, its presence is not synonym, nor are they identified in every liposarcoma.[1]


Inflammatory Liposarcoma

Dedifferentiated Liposarcoma

Myxoid Liposarcoma

Round Cell Liposarcoma

Pleomorphic Liposarcoma

Genetics

Associated Conditions

Gross Pathology

Microscopic Pathology

References

  1. 1.0 1.1 1.2 1.3 Dei Tos AP (2000). "Liposarcoma: new entities and evolving concepts". Ann Diagn Pathol. 4 (4): 252–66. doi:10.1053/adpa.2000.8133. PMID 10982304.


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