Lipoblast: morphologic features and diagnostic value

Overdiagnosis of atypical lipomatous tumors/well-differentiated liposarcomas by morphological diagnosis using only HE stained specimens: a case-control study with MDM2/CDK4 immunostaining and MDM2/CDK4 fluorescence in situ hybridization

BACKGROUND

Lipomatous tumors represent the most common type of soft tissue neoplasms. Mouse double minute 2 homolog (MDM2)/cyclin-dependent kinase 4 (CDK4) immunostaining is considered effective in differentiating between benign lipomas and intermediate malignant atypical lipomatous tumors/well-differentiated liposarcomas (ALT/WDLPSs). However, these tumors have traditionally been diagnosed histopathologically using hematoxylin and eosin-stained specimens, which is referred to here as morphological diagnosis. In this study, the accuracy of morphological diagnoses that had been made before MDM2/CDK4 immunostaining became available for distinguishing between lipoma and ALT/WDLPS was examined.

METHODS

The study participants were 109 patients with a morphological diagnosis of lipoma (68 patients) or ALT/WDLPS (41 patients) who had undergone surgical resection of the tumor in our hospital between 2009 and 2012. Tissue samples from all patients were used for MDM2/CDK4 immunostaining and the confirmation of MDM2/CDK4 amplification by fluorescence in situ hybridization (FISH).

RESULTS

Of the 41 patients with a morphological diagnosis of ALT/WDLPS, only 17 were positive for MDM2 FISH. In addition, one of the 68 patients with a morphological diagnosis of lipoma showed MDM2 amplification by FISH. When the definitive diagnosis of ALT/WDLPS was made by the positive results of MDM2 FISH, the sensitivity and specificity of morphological diagnosis were 41.5% and 98.5%, respectively. The sensitivity of MDM2 and CDK4 immunostaining was 55.6% and 40.0%, respectively, and their specificity was 87.0% and 84.6%, respectively. This indicates that the diagnostic accuracy of these immunostaining assays was not particularly high. The clinical features suggesting ALT/WDLPS were: patient age (older), maximum tumor diameter (large, cut-off value of 125 mm), tumor location (lower limb), and tumor depth (deep-seated).

CONCLUSIONS

Morphological diagnosis alone can accurately diagnose lipomas. However, it has a propensity to overdiagnose ALT/WDLPS. Thus, MDM2 FISH should be used more proactively, not only for lesions with obvious morphological abnormalities, but also for lipomatous tumors that are clinically suggestive of ALT/WDLPS.

FUS::DDIT3 Fusion Protein in the Development of Myxoid Liposarcoma and Possible Implications for Therapy

The FUS::DDIT3 fusion protein, formed by the chromosomal translocation t (12;16) (q13;p11), is found in over 90% of myxoid liposarcoma (MLS) cases and is a crucial protein in its development. Many studies have explored the role of FUS::DDIT3 in MLS, and the prevailing view is that FUS::DDIT3 inhibits adipocyte differentiation and promotes MLS growth and invasive migration by functioning as an aberrant transcription factor that affects gene expression and regulates its downstream molecules. As fusion proteins are gradually showing their potential as targets for precision cancer therapy, FUS::DDIT3 has also been investigated as a therapeutic target. Drugs that target FUS::DDIT3 and its downstream molecules for treating MLS are widely utilized in both clinical practice and experimental studies, and some of them have demonstrated promising results. This article reviews the findings of relevant research, providing an overview of the oncogenic mechanisms of the FUS::DDIT3 fusion protein in MLS, as well as recent advancements in its therapy.

Pleomorphic Liposarcoma Revisited

Pleomorphic liposarcoma (PLPS) is the rarest and more aggressive subtype of liposarcomas, accounting for 10% of all liposarcomas. The diagnosis should be considered after the detection of multivacuolated pleomorphic lipoblasts in biopsy specimens. Wide-margin resection is the treatment of choice. Complementary treatment options, such as radiation therapy and chemotherapy, are debatable in terms of their contribution to curing patients with PLPS. This article reviews the clinical, histopathological, and molecular characteristics of PLPS and discusses the latest trends in the management, therapeutic strategies, and novel investigations of the subject. [Orthopedics. 2023;46(2):e72-e80.].

A scoring system combining clinical, radiological, and histopathological examinations for differential diagnosis between lipoma and atypical lipomatous tumor/well-differentiated liposarcoma

This study evaluated the diagnostic accuracy of clinical, radiological, and histopathological examinations for differential diagnosis between atypical lipomatous tumor (ALT)/well-differentiated liposarcoma (WDLS) and lipoma, and aimed to develop a new combined scoring system for the preoperative diagnosis of ALT/WDLS. Eighty-nine lipomas and 56 ALT/WDLS were included and their clinical characteristics, magnetic resonance imaging (MRI) findings, histological findings by hematoxylin and eosin (HE) staining were investigated. Then, univariate and multivariate logistic regression analyses were performed for the findings, and a combined scoring system consisted of predictive factors of ALT/WDLS was developed. The univariate and multivariate logistic regression analyses revealed that tumor location (lower extremity), deep site, size (> 11 cm), thick septa (> 2 mm), enhancement of septa or nodular lesions, and lipoblasts were significantly different for the diagnosis of ALT/WDLS. We developed a combined scoring system based on the six predictive factors (total 0-16 points, the cutoff was 9 points). The area under the curve was 0.945, and sensitivity was 87.6% and specificity was 91.1% by the receiver operating characteristics curve. This combined scoring system does not require special equipment and reagents such as fluorescence in situ hybridization (FISH), and anyone can use it easily in many medical institutions with high diagnostic accuracy.

Spindle Cell Predominant Trichodiscoma or Spindle Cell Lipoma With Adnexal Induction? A Study of 25 Cases, Revealing a Subset of Cases With RB1 Heterozygous Deletion in the Spindle Cell Stroma

In our routine and consultative pathology practices, we have noticed that a relatively high proportion of spindle cell predominant trichodiscomas demonstrate a remarkable stromal admixture of adipose tissue, which along with spindle cells, prominent collagen bundles and myxoid change closely resembles spindle cell lipoma (SCL). To clarify their possible relationship to SCL, 25 cases of trichodiscoma and fibrofolliculoma with stromal "lipomatous metaplasia" were collected and examined using immunohistochemical stains [CD34 and retinoblastoma-1 (RB1) protein] and fluorescence in situ hybridization (RB1 deletion). The patients ranged in age from 35 to 81 years (median 64 years). The male to female ratio was almost equal (14:11). All tumors with a known location were situated on the face with a special predilection for the nose. All cases were sporadic, with all patients having a single lesion and showing no clinical features of Birt-Hogg-Dubé syndrome. No case with available follow-up presented with a recurrence or an otherwise aggressive clinical course. Spindle cell stroma was immunohistochemically positive for CD34 in 16 of 20 cases, and 18 of 19 cases showed loss of RB1 staining in lesional spindle cells. Fluorescence in situ hybridization analysis detected RB1 gene heterozygous deletion in 6 of 20 cases. We conclude that despite the SCL-like appearance of the investigated cases, the majority of them supposedly represent genuine spindle cell predominant trichodiscomas with adipose tissue admixture. However, there was a subset of histopathologically indistinguishable cases with proved RB1 deletion, which likely represent SCL with trichodiscoma/fibrofolliculoma-like epithelial/adnexal induction rather than spindle cell predominant variant of trichodiscoma.

Oral liposarcoma in elderly: Case report and literature analysis

RATIONALE

Oral liposarcoma is an extremely rare lesion that is often clinically misdiagnosed as a benign lesion because of its asymptomatic and indolent clinical course. we report a case of atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL) of buccal mucosa, provisionally diagnosed as lipoma.

PATIENT CONCERNS

A 97-year-old female was referred to dentistry and oral surgery department with an asymptomatic mass on the right buccal mucosa which had been present for an unknown period of time.

DIAGNOSIS

Magnetic resonance imaging demonstrated a well-circumscribed lesion at the right buccal mucosa, and a lipoma was suspected.

INTERVENTIONS

Surgical removal was performed, and a diagnosis of ALT/WDL was made. She and her family refused additional treatment due to her age.

OUTCOMES

At the 10 months follow-up, the patient remained free of disease.

LESSONS

The indolent clinical course and small size of oral liposarcoma can lead to provisional clinical diagnosis of benign lesion.

A challenging diagnosis of mesenchymal neoplasm of the colon: colonic dedifferentiated liposarcoma with lymph node metastases-a case report and review of the literature

PURPOSE

We report a case of primitive colonic dedifferentiated liposarcoma along with lymph node metastases.

METHODS

The patient's clinical, radiologic, surgical, and histologic data were reviewed, as well as the literature on colonic dedifferentiated liposarcoma with a focus on the incidence of lymph node metastasis in gastrointestinal sarcomas and on the differential diagnosis with other spindle cell tumors in the gastrointestinal tract.

RESULTS

A 53-year-old man was referred to our hospital with a 3 year-history of pain on the right back that was refractory to drugs. He performed an abdominal computed tomography scan which revealed a colonic wall thickening in the hepatic flexure and a few serosal nodularities. With these findings, the patient underwent an extended right hemicolectomy. On histopathologic examination, it turned out to be a colonic dedifferentiated liposarcoma with lymph node metastases.

CONCLUSIONS

The present case was a challenging diagnosis both at presurgical and histopathological level because it strongly mimicked a colonic adenocarcinoma. This was due to non-specific clinical and radiological presentation, to the non-characteristic histologic morphology and to the misleading presence of lymph node metastases. Malignant stromal tumors of the gastrointestinal tract beyond gist are fairly rare entities. Colonic dedifferentiated liposarcoma must be kept in mind and must be considered in the differential diagnosis of gastrointestinal tumors.

Pleomorphic liposarcoma: Updates and current differential diagnosis

Pleomorphic liposarcoma is the least common but most aggressive subtype of liposarcoma. Tumors most commonly arise in the deep soft tissues of the extremities in adult patients. Pleomorphic liposarcoma has no specific immunohistochemical or molecular genetic features, and the presence of lipoblasts remains the sole diagnostic criterion. Diagnostic challenges include the identification of lipoblasts, which are often scarce or focal, and the distinction from other pleomorphic sarcomas, including dedifferentiated liposarcoma with homologous lipoblastic differentiation. This review provides an updated overview of the clinicopathologic features of pleomorphic liposarcoma, with discussion of its morphologic variants, differential diagnosis, and the role of small biopsy samples.

Laryngeal Spindle Cell/Pleomorphic Lipoma: A Case Report. An In-Depth Review of the Adipocytic Tumors

Spindle cell and pleomorphic lipomas (SC/PLs) are a rare form of lipomatous tumors. They typically occur as a slow-growing localized mass in the subcutaneous fatty tissue of the posterior neck, back, and shoulders. This benign variant represents less than 1.5% of all lipomas and is relatively uncommon in the head and neck area. A manifestation in the larynx is even rarer. Unlike other anatomic locations, laryngeal lipomas can pose life-threatening symptoms secondary to acute obstruction of the upper aerodigestive tract. This report presents a case of a large SC/PL of the larynx associated with hoarseness, dysphagia, globus sensation, and neck fullness. The tumor was successfully removed through an anterior transcervical approach with infrahyoid myotomy. The authors review the literature concerning head and neck adipocytic tumors with spindle cells and discuss the difficulties in distinguishing SC/PLs from liposarcomas. To the best of the authors' knowledge, this is the first case to be reported in the oral and maxillofacial surgery literature.

Tongue Lumps and Bumps: Histopathological Dilemmas and Clues for Diagnosis

Exophytic lesions of the tongue encompass a diverse spectrum of entities. These are most commonly reactive, arising in response to local trauma but can also be neoplastic of epithelial, mesenchymal or miscellaneous origin. In most cases, the microscopic examination is likely to provide a straightforward diagnosis. However, some cases can still raise microscopic diagnostic dilemmas, such as conditions that mimic malignancies, benign tumors with overlapping features and anecdotal lesions. A series of "lumps and bumps" of the tongue are presented together with suggested clues that can assist in reaching a correct diagnosis, emphasizing the importance of the clinico-pathological correlations.

Lipoblasts in spindle cell and pleomorphic lipomas: a close scrutiny

The presence and frequency of lipoblasts (LPB) in spindle cell lipomas (SCL) and pleomorphic lipomas (PL) has never been studied in detail on a histologically, immunohistochemically and molecular genetically validated set of tumors. The authors investigated this feature by reviewing 91 cases of SCL and 38 PL. When more than 3 unequivocal LPB were found, the case was regarded as positive for the presence of LPB. All positive cases were then stained with CD34 and retinoblastoma (Rb) protein antibodies and tested by fluorescence in situ hybridization for MDM2 and CDK4 amplifications and the FUS gene rearrangements. The patients with SCL and PL containing LPB were 14 women and 47 men, the rest were of unknown gender. The cases usually presented as superficial, well-circumscribed soft tissue masses and most commonly occurred in the upper back and neck. CD34 was expressed in all cases, while Rb protein was consistently absent in all. Molecular genetic results, when available, were in concordance with the morphological diagnosis of SCL/PL. LPB were found in 37 (41%) cases of SCL and 25 cases of PL (66%). While in many cases they are inconspicuous, in some others they constitute a very prominent component of the tumor. It is important to be aware of this fact in order to avoid misinterpretation as liposarcoma.

[Adipocytic tumors]

Adipocytic tumors are the most common mesenchymal neoplasms, liposarcoma accounting for approximately 20% of soft tissue sarcomas. The differential diagnosis between benign and malignant tumors is often problematic and represents a significant proportion of consultation cases. The goal of this article is to review liposarcoma subtypes, the main benign adipocytic neoplasms: lipoblastoma, hibernoma, spindle/pleomorphic cell lipoma, chondroid lipoma, as well as non adipocytic neoplasms with a lipomatous component such as lipomatous solitary fibrous tumor, emphasizing on practical differential diagnosis issues, and immunohistochemical and molecular tools allowing their resolution.