Spindle Cell Lipoma with Ossification Mimicking Atypical Lipomatous Tumor/Well-Differentiated Liposarcoma: A Case Report

Although spindle cell lipoma (SCL) is a subtype of lipoma, the characteristics of SCL are observed in both lipomatous and non-lipomatous tumors. In this article, we present a case of SCL with ossification mimicking atypical lipomatous tumors/well-differentiated liposarcomas (ALTs/WDLs). Considering the findings of magnetic resonance imaging and needle biopsy, which exhibited ALTs/WDLs, marginal resection was performed. Histopathological findings demonstrated mature adipocytes and spindle cells without atypia and no malignant osteoid tissue in the ossified region. In addition, immunohistochemistry (IHC) showed positive staining for CD34, heterogeneous retinoblastoma protein deficiency, and negative staining for mouse double minute 2 homolog (MDM2) and cyclin-dependent kinase. Fluorescence in-situ hybridization showed negative amplification of MDM2. The final diagnosis of the tumor was established using IHC as an extremely rare SCL with ossification.

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Atypical Lipomatous Tumor/Well-Differentiated Liposarcoma With Features Mimicking Spindle Cell Lipoma

International Journal of Surgical Pathology ◽

10.1177/1066896919884648 ◽

2019 ◽

Vol 28 (3) ◽

pp. 336-340 ◽

Cited By ~ 1

Author(s):

Judith A. S. Jebastin ◽

Kyle D. Perry ◽

Dhananjay A. Chitale ◽

Michael P. Mott ◽

Jessica Sanchez ◽

...

Keyword(s):

Spindle Cell ◽

Spindle Cell Lipoma ◽

Rb1 Gene ◽

Prognostic Features ◽

Atypical Lipomatous Tumor ◽

Lipomatous Tumor ◽

Well Differentiated ◽

Mdm2 Amplification ◽

Lipomatous Tumors

Atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL) and spindle cell lipoma are lipomatous tumors with distinct clinical, molecular, and prognostic features. Although histological and immunophenotypic features can overlap between ALT/WDL and spindle cell lipoma, the oncogenesis and clinical behavior are markedly different. In borderline cases, molecular analysis for MDM2 or CDK4 amplification can aid in distinguishing ALT/WDL from spindle cell lipoma. Although dedifferentiated liposarcoma has been reported to harbor both MDM2 amplification and loss of the RB1 region, we are not aware of a reported RB1 loss in well-differentiated ALT/WDL. In this article, we present a 69-year-old woman with a lipomatous tumor in the gluteal region that histologically, immunohistochemically, and molecularly mimicked spindle cell lipoma (with positive immunohistochemical staining for CD34 and loss of the RB1 gene region), yet harbored amplification of MDM2 and CDK4 confirmed by fluorescence in situ hybridization, supporting classification as ALT/WDL. This case strengthens the argument that in atypical clinical contexts, molecular studies for MDM2/CDK4 should be considered in tumors resembling spindle cell lipoma.

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Spindle Cell Lipoma of the Foot and the Application of CD34 Immunohistochemistry to Atypical Lipomatous Tumors in Unusual Locations

Applied Immunohistochemistry & Molecular Morphology ◽

10.1097/00129039-200009000-00009 ◽

2000 ◽

Vol 8 (3) ◽

pp. 222-227 ◽

Cited By ~ 3

Author(s):

Cary D. Austin ◽

Jon R. Tiessen ◽

Anuradha Gopalan ◽

Jesse M. Williams ◽

Charles D. Bangs ◽

...

Keyword(s):

Spindle Cell ◽

Spindle Cell Lipoma ◽

Atypical Lipomatous Tumors ◽

Lipomatous Tumors

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Automated Bright-Field Dual-Color In Situ Hybridization for MDM2: Interobserver Reproducibility and Correlation With Fluorescence In Situ Hybridization in a Series of Soft Tissue Consults

Archives of Pathology & Laboratory Medicine ◽

10.5858/arpa.2015-0249-oa ◽

2016 ◽

Vol 140 (10) ◽

pp. 1111-1115 ◽

Cited By ~ 6

Author(s):

Gloria Zhang ◽

Christopher P. Lanigan ◽

John R. Goldblum ◽

Raymond R. Tubbs ◽

Erinn Downs-Kelly

Keyword(s):

In Situ Hybridization ◽

Fluorescence In Situ Hybridization ◽

Chromosome 12 ◽

Interobserver Reproducibility ◽

Bright Field ◽

Well Differentiated ◽

Atypical Lipomatous Tumors ◽

Mdm2 Amplification ◽

Lipomatous Tumors

Context.—Atypical lipomatous tumors/well-differentiated liposarcomas contain alterations in the 12q13-15 region resulting in amplification of MDM2 and nearby genes. Identifying MDM2 amplification is a useful ancillary test, as the histologic mimics of atypical lipomatous tumors/well-differentiated liposarcomas have consistently shown a lack of MDM2 amplification. Objective.—To assess the interobserver reproducibility of a bright-field assay for MDM2 amplification (dual-color, dual-hapten in situ hybridization [DDISH]) among reviewers with varying degrees of experience with the assay and to assess the concordance of MDM2 DDISH with MDM2 fluorescence in situ hybridization (FISH). Design.—In total, 102 cases were assessed in parallel for MDM2 by FISH and DDISH. MDM2 amplification was defined as an MDM2 to chromosome 12 ratio of 2.0 or greater, whereas an MDM2 to chromosome 12 ratio of less than 2 was nonamplified. Fluorescence in situ hybridization was scored in the routine clinical laboratory and DDISH was evaluated by 3 different pathologists blinded to the final diagnosis and FISH results. Results.—Fluorescence in situ hybridization categorized 27 cases (26%) as MDM2 amplified and 75 cases (74%) as nonamplified; the consensus DDISH diagnosis was 98% concordant with FISH. Agreement between MDM2 DDISH by each reviewer and MDM2 FISH was highly concordant (99%, 98%, and 98%, respectively, for reviewers 1, 2 and 3). The κ agreement of the 3 reviewers scoring DDISH was excellent (κ = 0.949, 0.95, and 0.95, respectively, for reviewers 1, 2, and 3). Conclusions.—This study highlights excellent concordance between DDISH and FISH in MDM2 copy number assessment. Moreover, excellent interobserver reproducibility of the DDISH assay was found among reviewers with varying levels of experience evaluating bright-field assays.

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FluorescenceIn SituHybridization forMDM2Amplification as a Routine Ancillary Diagnostic Tool for Suspected Well-Differentiated and Dedifferentiated Liposarcomas: Experience at a Tertiary Center

Sarcoma ◽

10.1155/2015/812089 ◽

2015 ◽

Vol 2015 ◽

pp. 1-10 ◽

Cited By ~ 38

Author(s):

Khin Thway ◽

Jayson Wang ◽

John Swansbury ◽

Toon Min ◽

Cyril Fisher

Keyword(s):

Gene Amplification ◽

Diagnostic Tool ◽

Spindle Cell ◽

Significant Group ◽

Lipomatous Tumor ◽

Tertiary Center ◽

Benign Histology ◽

Well Differentiated ◽

Correlation Rate

Background. The assessment ofMDM2gene amplification by fluorescencein situhybridization (FISH) has become a routine ancillary tool for diagnosing atypical lipomatous tumor (ALT)/well-differentiated liposarcoma and dedifferentiated liposarcoma (WDL/DDL) in specialist sarcoma units. We describe our experience of its utility at our tertiary institute.Methods. All routine histology samples in whichMDM2amplification was assessed with FISH over a 2-year period were included, and FISH results were correlated with clinical and histologic findings.Results. 365 samples from 347 patients had FISH forMDM2gene amplification. 170 were positive (i.e., showedMDM2gene amplification), 192 were negative, and 3 were technically unsatisfactory. There were 122 histologically benign cases showing a histology:FISH concordance rate of 92.6%, 142 WDL/DDL (concordance 96.5%), and 34 cases histologically equivocal for WDL (concordance 50%). Of 64 spindle cell/pleomorphic neoplasms (in which DDL was a differential diagnosis), 21.9% showedMDM2amplification. Of the cases with discrepant histology and FISH, all but 3 had diagnoses amended following FISH results. For discrepancies of benign histology but positive FISH, lesions were on average larger, more frequently in “classical” (intra-abdominal or inguinal) sites for WDL/DDL and more frequently core biopsies. Discrepancies of malignant histology but negative FISH were smaller, less frequently in “classical” sites but again more frequently core biopsies.Conclusions. FISH has a high correlation rate with histology for cases with firm histologic diagnoses of lipoma or WDL/DDL. It is a useful ancillary diagnostic tool in histologically equivocal cases, particularly in WDL lacking significant histologic atypia or DDL without corresponding WDL component, especially in larger tumors, those from intra-abdominal or inguinal sites or core biopsies. There is a significant group of well-differentiated adipocytic neoplasms which are difficult to diagnose on morphology alone, in which FISH forMDM2amplification is diagnostically contributory.

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