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, since multiple benign lesions may contain lipoblasts; nor are they identified in every [[liposarcoma]], as its absence does not prevent the diagnosis of the condition, if remaining criteria are met.  Lipoblasts may <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, since multiple benign lesions may contain lipoblasts; nor are they identified in every [[liposarcoma]], as its absence does not prevent the diagnosis of the condition, if remaining criteria are met.<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>
====Inflammatory Liposarcoma====
Its adipocitic nature may be misidentified due to the heavy chronic inflammatory infiltrate.<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>
 




====Inflammatory Liposarcoma====


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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.
In 1994, a rare variant of well-differentiated liposar- coma was described under the term spindle cell liposar- coma,8,9 which occurs in adults and, at least in the first series, appeared to relatively often involve subcutaneous soft tissue. However, through observation of a larger number of cases, the anatomic distribution of spindle cell liposarcoma seems to be comparable to that of the other well-differentiated liposarcoma subtypes. Morpho- logically, spindle cell liposarcoma is composed of a fairly bland neural-like spindle cell proliferation set in a fibrous and/or myxoid background (Fig 6) and is associ- ated with an atypical lipomatous component that usu- ally includes lipoblasts (Fig 7). Main differential diag- noses include spindle cell lipoma (composed of bland, sometimes palisading, CD34-positive spindle cells, ad- mixed with eosinophilic refractile collagen bundles), neurofibroma (characterized by a less cellular S-100– positive spindle cell proliferation with wavy nuclei), dermatofibrosarcoma protuberans (cytologically bland, monomorphic CD34-positive spindle cell proliferation organized in a distinctive storiform growth pattern and characterized by tendency to infiltrate the surrounding fat in a peculiar ‘‘honeycomb’’ pattern), malignant peripheral nerve sheath tumor (generally highly cellular tumors composed of tapering or wavy spindle cells featuring perivascular accentuation and focal S-100– positive immunoreactivity in approximately 50% of cases), and well-differentiated sclerosing liposarcoma (characterized by the presence of bizarre hyperchro- matic stromal cells set in fibrillary collagen). The pres- ence of an atypical lipomatous component also permits distinction from low-grade fibromyxoid sarcoma (Evans’ tumor). Interestingly, spindle cell liposarcoma exhibits chromosome changes (ring chromosomes and giant marker chromosomes) identical to those observed in other members of the well-differentiated liposarcoma group, thus validating its classification.
In 1994, a rare variant of well-differentiated liposar- coma was described under the term spindle cell liposar- coma,8,9 which occurs in adults and, at least in the first series, appeared to relatively often involve subcutaneous soft tissue. However, through observation of a larger number of cases, the anatomic distribution of spindle cell liposarcoma seems to be comparable to that of the other well-differentiated liposarcoma subtypes. Morpho- logically, spindle cell liposarcoma is composed of a fairly bland neural-like spindle cell proliferation set in a fibrous and/or myxoid background (Fig 6) and is associ- ated with an atypical lipomatous component that usu- ally includes lipoblasts (Fig 7). Main differential diag- noses include spindle cell lipoma (composed of bland, sometimes palisading, CD34-positive spindle cells, ad- mixed with eosinophilic refractile collagen bundles), neurofibroma (characterized by a less cellular S-100– positive spindle cell proliferation with wavy nuclei), dermatofibrosarcoma protuberans (cytologically bland, monomorphic CD34-positive spindle cell proliferation organized in a distinctive storiform growth pattern and characterized by tendency to infiltrate the surrounding fat in a peculiar ‘‘honeycomb’’ pattern), malignant peripheral nerve sheath tumor (generally highly cellular tumors composed of tapering or wavy spindle cells featuring perivascular accentuation and focal S-100– positive immunoreactivity in approximately 50% of cases), and well-differentiated sclerosing liposarcoma (characterized by the presence of bizarre hyperchro- matic stromal cells set in fibrillary collagen). The pres- ence of an atypical lipomatous component also permits distinction from low-grade fibromyxoid sarcoma (Evans’ tumor). Interestingly, spindle cell liposarcoma exhibits chromosome changes (ring chromosomes and giant marker chromosomes) identical to those observed in other members of the well-differentiated liposarcoma group, thus validating its classification.



Revision as of 16:12, 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, since multiple benign lesions may contain lipoblasts; nor are they identified in every liposarcoma, as its absence does not prevent the diagnosis of the condition, if remaining criteria are met.[1]

Inflammatory Liposarcoma

Its adipocitic nature may be misidentified due to the heavy chronic inflammatory infiltrate.[1]



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 1.4 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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