MDM2 and CDK4 Immunostainings Are Useful Adjuncts in Diagnosing Well-Differentiated and Dedifferentiated Liposarcoma Subtypes

Getting under the skin: The role of CDK4/6 in melanomas

Melanoma is the deadliest type of cancer that affects the largest organ of our body, the skin. In recent years, there is an increase in the incidence and aggressiveness of melanomas. The number of treatment options has grown considerably in the past few years, leading to significant improvements in both overall and progression-free survival. One of the attractive candidates in this wave of treatment options is a cell cycle controller: cyclin-dependent kinases (CDK) 4/6 inhibitors. CDK4/6, a class of serine/threonine kinases expressed in most cell types, controls the first gap phase (G1 to S) of the cell cycle, indicating its vital importance in both normal cellular processes as well as tumorigenesis. Up to 90% of melanoma patients have genomic mutations affecting various parts of CDK4/6 pathway. Noticeably, with the help of next-generation sequencing technology, mutations with high frequency in the CDK4 pathway were also identified in relatively rare subtypes of melanoma including acral melanoma and mucosal melanoma. Therefore, CDK4/6 inhibitors have emerged as powerful and promising anticancer therapies, especially in combination treatment with immunotherapies or other targeted therapies. In this review, we will provide an overview of current scientific knowledge regarding the oncogenic properties of CDK4/6 in melanomas, we mainly discuss the latest genomic and preclinical findings of CDK4 signaling in melanoma, the progress of CDK4 inhibition as combined with other therapies for overcoming resistance and summarize recent advances from clinical trials as well as ongoing studies which gives us a better scope into the effectiveness of CDK4/6 therapy in treating malignant melanomas.

Metastatic Biphasic Primitive Tumor in the Mandible of a Child

Pediatric mandibular tumors present an aggressive biological behavior and difficult diagnosis. A wide range of odontogenic and nonodontogenic tumors comprise the spectrum of these lesions. We report a case of a 1-year-old male child patient showing facial asymmetry symptomatic of an expansive lesion extending throughout the body and ramus of the left hemimandible with a diameter of 8 cm. The histopathological report suggested a high-grade mucoepidermoid carcinoma (MEC), recommending further immunohistochemical investigation of the ectomesenchymal or neuroectodermal origin of the tumor cells. The patient evolved with extensive bilateral pleural effusion followed by metastasis in the middle third of the right humerus, and died 2 months after the first biopsy procedure by acute renal failure with tubular necrosis, before a final inconclusive immunohistochemical report was reached. The lack of resources for less-favored regions of Brazil impairs rapid biomolecular examinations such as immunohistochemical resulting in delay of appropriate therapeutic procedures.

An Algorithmic Immunohistochemical Approach to Define Tumor Type and Assign Site of Origin

Immunohistochemistry represents an indispensable complement to an epidemiology and morphology-driven approach to tumor diagnosis and site of origin assignment. This review reflects the state of my current practice, based on 15-years' experience in Pathology and a deep-dive into the literature, always striving to be better equipped to answer the age old questions, "What is it, and where is it from?" The tables and figures in this manuscript are the ones I "pull up on the computer" when I am teaching at the microscope and turn to myself when I am (frequently) stuck. This field is so exciting because I firmly believe that, through the application of next-generation immunohistochemistry, we can provide better answers than ever before. Specific topics covered in this review include (1) broad tumor classification and associated screening markers; (2) the role of cancer epidemiology in determining pretest probability; (3) broad-spectrum epithelial markers; (4) noncanonical expression of broad tumor class screening markers; (5) a morphologic pattern-based approach to poorly to undifferentiated malignant neoplasms; (6) a morphologic and immunohistochemical approach to define 4 main carcinoma types; (7) CK7/CK20 coordinate expression; (8) added value of semiquantitative immunohistochemical stain assessment; algorithmic immunohistochemical approaches to (9) "garden variety" adenocarcinomas presenting in the liver, (10) large polygonal cell adenocarcinomas, (11) the distinction of primary surface ovarian epithelial tumors with mucinous features from metastasis, (12) tumors presenting at alternative anatomic sites, (13) squamous cell carcinoma versus urothelial carcinoma, and neuroendocrine neoplasms, including (14) the distinction of pheochromocytoma/paraganglioma from well-differentiated neuroendocrine tumor, site of origin assignment in (15) well-differentiated neuroendocrine tumor and (16) poorly differentiated neuroendocrine carcinoma, and (17) the distinction of well-differentiated neuroendocrine tumor G3 from poorly differentiated neuroendocrine carcinoma; it concludes with (18) a discussion of diagnostic considerations in the broad-spectrum keratin/CD45/S-100-"triple-negative" neoplasm.

Endometrial stromal sarcomas with BCOR-rearrangement harbor MDM2 amplifications

Recently a novel subtype of endometrial stromal sarcoma (ESS) defined by recurrent genomic alterations involving BCOR has been described (HGESS‐BCOR). We identified a case of HGESS‐BCOR with a ZC3H7B‐BCOR gene fusion, which harbored an amplification of the MDM2 locus. This index case prompted us to investigate MDM2 amplification in four additional cases of HGESS‐BCOR. Tumors were analyzed for MDM2 amplification by array‐based profiling of copy number alterations (CNAs) and fluorescence in situ hybridization (FISH), as well as for MDM2 expression by immunohistochemistry (IHC). Additionally, a cohort of other mesenchymal uterine neoplasms, including 17 low‐grade ESS, 6 classical high‐grade ESS with YWHAE‐rearrangement, 16 uterine tumors resembling ovarian sex cord tumors, 7 uterine leiomyomas and 8 uterine leiomyosarcomas, was analyzed for CNAs in MDM2. Copy number profiling identified amplification of the 12q15 region involving the MDM2 locus in all five HGESS‐BCOR. Subsequent validation analyses of three tumors confirmed MDM2 amplification using MDM2 FISH. Accordingly, IHC showed MDM2 overexpression in all analyzed cases. None of the other uterine neoplasms in our series, including tumors that are in the histopathological differential diagnoses of HGESS‐BCOR, showed copy number gains of MDM2. Together, our results indicate that HGESS‐BCOR carries MDM2 amplifications, which has diagnostic implications and could potentially be used for targeted therapies in these clinically aggressive tumors.

Primary Orbital Dedifferentiated Liposarcoma

BACKGROUND

Primary dedifferentiated liposarcoma of the orbit is a rare condition.

CASE DESCRIPTION

A 41-year-old man presented with a history of right ophthalmalgia with eye movement and exophthalmos that had developed 2 months earlier. Neuroimages revealed a right orbital mass located above the superior rectus muscle. Tumor resection through the right frontal craniotomy was performed. Histopathologic findings showed the dedifferentiated liposarcoma.

CONCLUSIONS

Primary orbital dedifferentiated liposarcomas remain challenging for their diagnosis and standard treatment. Clinicians should keep in mind the possibility of liposarcoma with orbital tumors.

The Utility of Perilipin in Liposarcomas: PLIN1 Differentiates Round Cell Liposarcoma From Other Round Cell Sarcomas

Liposarcoma is the most common soft tissue sarcoma in adults; however, accurate diagnosis often depends on the use of ancillary molecular testing which can be time consuming and expensive. Myxoid/round cell liposarcoma may be a diagnostic challenge due to the morphologic similarities with other nonadipocytic sarcomas with round cell morphology. Immunohistochemistry may be a helpful adjunct to appropriately triage cases for molecular testing. Perilipin 1 (PLIN1) and perilipin 2 (adipophilin) (PLIN2) are intracellular proteins involved in lipid droplet formation, which we hypothesized may be useful as immunohistochemical markers for liposarcoma. Using archival tumor tissue, we assessed pattern of PLIN1 and PLIN2 expression in 46 adipocytic tumors and 36 nonadipocytic sarcomas. PLIN1 was expressed in 88% of liposarcomas, including 100% of myxoid/round cell liposarcomas, and did not have any expression in nonadipocytic sarcomas. PLIN1 was not expressed in dedifferentiated liposarcoma. Although PLIN2 demonstrates increased sensitivity for liposarcoma, including expression in dedifferentiated liposarcoma, it is not specific for adipocytic differentiation and is expressed in other nonadipocytic sarcomas. Furthermore, PLIN2 is not expressed in lipoma-like well-differentiated liposarcoma, and as such has limited diagnostic utility.

Comprehensive Review of Abdominopelvic Mesenchymal Tumors with Radiologic Pathologic Correlation and Update on Current Treatment Guidelines - Part 1

Soft-tissue sarcomas are a diverse group of rare mesenchymal malignancies accounting for only 1% of all solid adult malignancies. These have been categorized in 12 broad groups by the World Health Organization (WHO) with their recent update in 2013. Majority of them lack specific imaging features serving as imaging conundrums for a radiologist. These are often large masses at presentation as they are asymptomatic or cause vague clinical symptoms. These tumors are challenging for surgeons as well as they find it difficult to achieve complete resection because of complex intra-abdominal anatomy and their close relationship with critical structures. Often, a multidisciplinary approach is required to decide on the most appropriate management for these complex cases so as to provide optimal patient care. Knowledge of the WHO classification, pathologic features and available treatment options will help the radiologist make a meaningful contribution in multidisciplinary discussions of such cases and overall patient care. Liposarcoma (well-differentiated and dedifferentiated liposarcomas), leiomyosarcoma, and gastrointestinal stromal tumor are the 3 most common primary intra-abdominal sarcomas. In part 1 of this article, general features of soft tissue sarcomas and some of the common tumors from WHO category 1-4 found in abdomen and pelvis are discussed. Part 2 will focus on common tumors from remainder of the WHO categories.

Expanding the differential of cutaneous epithelioid tumors: A case of dedifferentiated liposarcoma with epithelioid features involving the skin, with review of the literature

Liposarcomas are categorized into four distinct histopathological subtypes: atypical lipomatous tumors (ALT)/well-differentiated liposarcoma (WDL), dedifferentiated, myxoid, and pleomorphic. Dedifferentiated liposarcomas account for approximately 18% of all liposarcomas, characteristically arising in the deep soft tissue. They are reported to have lower rates of metastasis compared to other pleomorphic sarcomas.^{1 -3} The classic histopathologic appearance is ALT/WDL admixed or juxtaposed with a predominantly nonlipogenic sarcoma. Epithelioid features are rare, appearing in as few as 3% of tumors, and have not previously been reported in a superficial location. Herein, we present a 57-year-old male with intradermal and subcutaneous metastasis of his known deep dedifferentiated liposarcoma with epithelioid features. By H&E the tumor featured cords and sheets of crowded, plump, epithelioid cells with thick nuclear membranes and prominent nucleoli, which raised a broad differential including carcinoma and melanoma. By immunohistochemistry the tumor was diffusely positive for MDM2 and CDK4, on the other hand stains for Sox10, Melan A, MITF, CKAE1/3, desmin, and S100 protein were negative. This case serves as an opportunity to raise awareness of this rare morphological subtype, which can involve the skin and mimic epithelial and melanocytic malignancies. It can be a potential diagnostic pitfall, especially if metastases are the first presentation.

The Utility of MDM2 and CDK4 Immunohistochemistry and MDM2 FISH in Craniofacial Osteosarcoma

Craniofacial osteosarcoma is rare (2-10% of all osteosarcomas). Most low grade fibroblastic osteosarcomas of the long bones are characterized by amplification of chromosome12q including MDM2 and CDK4 genes. This study aims to investigate the utility of MDM2 and CDK4 immunostains as well as MDM2 FISH in craniofacial osteosarcomas as a means of distinguishing them from benign fibro-osseous lesions. Cases of primary osteosarcoma and benign fibro-osseous lesions of the craniofacial bones were identified in the diagnostic pathology archives. MDM2 (SMP14 and/or IF2) and CDK4 (D9G3E and/or DCS-31) immunostains were performed on a representative block from each osteosarcoma and benign case. Fluorescence in situ hybridization (FISH) for MDM2 was performed on non-decalcified osteosarcomas. In osteosarcomas, the rate of expression of either MDM2 IF2, MDM2 SMP14, CDK4 DCS-31, or CDK4 D9G3E was 72.7% (8/11 cases), usually focal and weak. Using the MDM2 IF2 clone and the CDK4 DCS-31 clone, MDM2 and CDK4 were negative in lesional cells in all 14 benign fibro-osseous lesions. Using the IF2 and SMP14 clones, MDM2 nuclear expression was present in associated osteoclast-like giant cells in both benign and malignant cases. Of 4 successful cases, 1 high grade osteosarcoma was positive for MDM2 amplification. MDM2 or CDK4 expression or MDM2 amplification may aid in a diagnosis of head and neck osteosarcoma. However, when absent, sarcoma is not excluded. Due to focal weak expression of MDM2 in tumor cells in conjunction with nuclear expression in associated giant cells, caution should be exercised when interpreting positive stains.

Surgical management of truncal and extremities atypical lipomatous tumors/well-differentiated liposarcoma: A systematic review of the literature

INTRODUCTION

Atypical lipomatous tumors or well-differentiated liposarcomas (ALT/WDLS) are low-grade soft tissue tumors that are commonly located on the trunk and extremities. There is no consensus on the best surgical approach for ALT/WDLS.

METHODS

A systematic literature review of PubMed, Medline, Embase, Scopus, and google scholar was performed. All published studies on trunk or extremities ALT/WDLS with reported outcome data were considered and independently screened for inclusion by at least two of the authors.

RESULTS

A total of eighteen studies comprising 793 patients with ALT/WDLS were included. 580 patients underwent marginal excision, with local recurrence observed in 69 (11.9%). 213 patients underwent wide excision with local recurrence in 7(3.3%). Recurrent tumors were successfully re-resected with marginal or wide excision. Dedifferentiation was confirmed in 9 patients (1.1%), and a distant pulmonary metastasis in 1 patient (0.1%).

DISCUSSION

Marginal excision of truncal or extremities ALT/WDLS results in a slightly higher local recurrence rate. However, recurrences are almost always amenable to re-resection. The findings support the use of marginal excision for truncal or extremities ALT/WDLS.

Precision Medicine in Soft Tissue Sarcoma Treatment

Soft tissue sarcoma (STS) is a rare component of malignant diseases. STS includes various histological subtypes, and there are some important differences among the different histological subtypes regarding the mutation profile and sensitivity to antitumor agents. Many clinical trials of STS incorporating many different histological subtypes in various populations have been conducted; it is difficult to compare the findings and make conclusions about clinical efficacy. Targeted therapies focusing on specific histological subtypes and precision therapy focusing on the specific genetic mutation(s) of each STS patient are being investigated. Since STS patients are a small population, new clinical trial designs are required to evaluate and establish new targeted therapies for each histological subtype that has a limited number of patients, and preclinical investigations are needed to detect targetable mutations. Now that cancer genome profiling is used in clinical practice, it is urgently necessary to connect the genome profiling data obtained in clinical settings to the optimal clinical treatment strategies. Herein we review the development and challenges of precision therapy in the management of STS patients.

Primary gastrointestinal liposarcoma-a clinicopathological study of 8 cases of a rare entity

Primary gastrointestinal liposarcoma is rare, and information regarding this entity is largely based on single case studies. We report on 8 patients with primary liposarcoma of the gastrointestinal tract and review the pertinent literature. The cohort includes 6 men and 2 women who ranged in age from 51 to 81 years (median 68.5). Two tumors arose in the stomach, 4 in the small intestine, and 2 in the large intestine. Tumors ranged in size from 2.5 to 14.5 cm (median 7 cm), originated in the submucosa or muscularis propria of the intestinal wall, and frequently protruded into the bowel lumen, resulting in mucosal ulceration and luminal obstruction. Six tumors were dedifferentiated liposarcomas, and 2 were well-differentiated liposarcoma. Surgical excision was performed on all tumors except for 1 case of dedifferentiated liposarcoma. On follow-up, 1 patient with dedifferentiated liposarcoma developed a lytic sacral lesion suspicious for metastasis 4 months after resection of the primary, and another underwent marginal resection and presented with recurrence 4 years later, had tumor re-resection, and was considered disease-free at 6 weeks postsurgery. A third patient with dedifferentiated liposarcoma was alive with unknown disease status at 17 months following surgery, and another patient with dedifferentiated liposarcoma was alive without evidence of disease at 30 months following surgery. No follow-up information on the remaining patients is available. Overall, liposarcomas of the intestinal tract are most frequently high-grade dedifferentiated tumors that are biologically aggressive and require surgical excision with widely negative margins to help reduce the risk of local recurrence and dissemination. Important in the differential diagnosis is malignant gastrointestinal stromal tumor. Care must be taken not to misdiagnose one entity for the other because the correct diagnosis carries important therapeutic implications.

Lipomatous Soft Tissue Masses: Challenging the Paradigm of Routine Preoperative Biopsy

BACKGROUND

Lipomatous masses are the most common soft tissue tumors. While the majority are benign lipomas, it is important to identify those masses that are malignant prior to excision. Current guidelines recommend core needle biopsy (CNB) for all lipomatous masses larger than 3-5 cm. The objective of this study was to determine if routine preoperative CNB based on mass size is necessary, or if radiographic features can guide the need for CNB.

MATERIALS AND METHODS

Patients who underwent excision of extremity or truncal lipomatous masses at a single institution from October 2014 to July 2017 were retrospectively reviewed. By protocol, preoperative imaging was routinely obtained for all masses larger than 5 cm. High-risk radiographic features (intramuscular location, septations, nonfat nodules, heterogeneity, and ill-defined margins) and surgical pathology were evaluated to determine patients most likely to benefit from preoperative CNB.

RESULTS

Of 178 patients, 2 (1.1%) had malignant tumors on surgical pathology. All masses smaller than 5 cm were benign and, if imaging was obtained, had two or fewer high-risk radiographic features. Both of the patients with malignant tumors had masses larger than 5 cm, preoperative imaging that showed at least four high-risk radiographic features, and underwent CNB prior to excision.

CONCLUSIONS

The overall rate of malignancy is very low. The results of this study suggest that lipomatous masses smaller than 5 cm without concerning clinical characteristics do not require preoperative imaging or CNB. Conversely, lipomatous masses larger than 5 cm should undergo routine MRI with subsequent CNB if multiple high-risk radiographic features are present.

Immunohistochemistry as a Genetic Surrogate in Dermatopathology: Pearls and Pitfalls

Immunohistochemistry (IHC) is routinely performed in most laboratories, and other than purchase of commercially available antibodies, requires no additional equipment or reagents. As such, IHC is an accessible and relatively inexpensive test and one that can be performed quite quickly. This is in sharp contrast to genomic or mutational testing methodologies that are routinely "send out" tests as they require specialized equipment and reagents as well as individuals with expertise in the performance of the tests and analysis of the results, resulting in a prolonged turn-round-time and enhanced associated costs. However, many open questions remain in a rapidly changing therapeutic and scientific landscape with most obvious one being what exactly is the utility of "good old fashioned" IHC in the age of targeted therapy? For molecular applications, is a negative immunohistochemical result enough as a stand-alone diagnostic or predictive product? Is a positive immunohistochemical result perhaps more suitable for a role in screening for molecular alterations rather than a definitive testing modality? This review is an attempt to answer those very questions. We elucidate the broad range of entities in which IHC is currently used as a molecular surrogate and underscore pearls and pitfalls associated with each. Special attention is given to entities for which targeted therapies are currently available and to entities in which molecular data is of clinical utility as a prognosticator.

Distribution of intramuscular giant lipomas in the functional compartments of the forearm: a report of 12 cases

PURPOSE

The aim of this study was to investigate the distribution of intramuscular giant lipomas in the functional compartments of the forearm and to compare their clinical, radiological and histopathological features with those reported in the current literature.

METHODS

The study included 12 patients who were surgically treated for intramuscular lipomas > 5 cm in size located in the forearm that had been confirmed histopathologically between April 2006 and March 2017. Data about the patients with respect to age, sex, affected side, localisation of the lipomas in the forearm functional compartments, size, histopathological features and recurrence were collected. According to the clinical complaints, direct radiography and magnetic resonance imaging were applied.

RESULTS

The average diameter was 6.5 cm (range: 5.5-9 cm). All lipomas had a well-defined border. All the patients presented with soft-tissue masses that were painless in seven patients. Five patients had nerve compression symptoms. When the lipomas were classified according to the functional compartments of the forearm, six of them were located in the superficial volar compartment, two in the deep volar compartment, two in the deep dorsal compartment and two in the lateral compartment. All lipomas were surgically removed by marginal excision. None had complications or recurrence at a mean of 6.5 years follow-up (range: 1-12 years) after surgery.

CONCLUSIONS

Intramuscular lipoma is a relatively uncommon tumour, especially in the forearm. Because of the proximity to the neurovascular structures in the forearm, excision of lipomas should be performed with care and include wide incisions. Additionally, knowing the anatomical features of the compartment where the lipoma is localised in the forearm is important in planning surgery to enable easier dissection of the lipoma and lessen the risk of damage to adjacent neurovascular structures.

LEVEL OF EVIDENCE

Level 4.

Inhibition of histone deacetylase 2 reduces MDM2 expression and reduces tumor growth in dedifferentiated liposarcoma

Dedifferentiated liposarcoma (DDLPS) is a highly morbid mesenchymal tumor characterized and driven by genomic amplification of the MDM2 gene. Direct inhibition of MDM2 has shown promise pre-clinically, but has yet to be validated in clinical trials. Early in vitro studies have demonstrated that pan-histone deacetylase (HDAC) inhibition may have anti-MDM2 effects. Here we present in silico, in vitro, and mouse xenograft studies that suggest that specifically targeting HDAC2 reduces MDM2 expression and has anti-tumor affects in DDLPS. Two independent datasets, The Cancer Genome Atlas (TCGA; n = 58) and the Memorial Sloan-Kettering Cancer Center Dataset (MSKCC; n = 63), were used to identify the co-expression between class I HDACs and MDM2, and their clinical impact. HDAC2 was highly co-expressed with MDM2 (TCGA: Spearman’s coefficient = 0.29, p = 0.03; MSKCC: Spearman’s coefficient = 0.57, p < 0.001). As both a continuous and dichotomous predictor, elevated HDAC2 expression was associated with worsened disease-free survival in the TCGA (Continuous: Hazard-ratio (HR) 1.7; 95% Confidence Interval (95%CI) 0.97–2.9; p = 0.06; Dichotomous: HR 7.1, 95%CI 2.5–19.8, p < 0.001) and distant recurrence-free survival in the MSKCC (Continuous: HR 2.2; 95%CI 1.1–4.8; p = 0.04; Dichotomous: HR 2.8, 95%CI 1.2–6.4, p = 0.02). In vitro, treatment of DDLPS cell lines with the HDAC inhibitors MI-192 (HDAC2/3 inhibitor) or romidepsin (HDAC1/2 inhibitor) reduced MDM2 expression and induced apoptosis. In a murine DDLPS xenograft model, romidepsin reduced tumor growth and lowered tumor MDM2 expression. RNA-sequencing of romidepsin treated mouse tumors demonstrated markers of TP53 reactivation. Taken together, our data supports the hypothesis that targeting HDAC2 may represent a potential strategy to modulate MDM2 expression in DDLPS.

Molecular phenotyping using networks, diffusion, and topology: soft tissue sarcoma

Many biological datasets are high-dimensional yet manifest an underlying order. In this paper, we describe an unsupervised data analysis methodology that operates in the setting of a multivariate dataset and a network which expresses influence between the variables of the given set. The technique involves network geometry employing the Wasserstein distance, global spectral analysis in the form of diffusion maps, and topological data analysis using the Mapper algorithm. The prototypical application is to gene expression profiles obtained from RNA-Seq experiments on a collection of tissue samples, considering only genes whose protein products participate in a known pathway or network of interest. Employing the technique, we discern several coherent states or signatures displayed by the gene expression profiles of the sarcomas in the Cancer Genome Atlas along the TP53 (p53) signaling network. The signatures substantially recover the leiomyosarcoma, dedifferentiated liposarcoma (DDLPS), and synovial sarcoma histological subtype diagnoses, and they also include a new signature defined by activation and inactivation of about a dozen genes, including activation of serine endopeptidase inhibitor SERPINE1 and inactivation of TP53-family tumor suppressor gene TP73.

Phase 1 study of the MDM2 inhibitor AMG 232 in patients with advanced P53 wild-type solid tumors or multiple myeloma

Background This open-label, first-in-human, phase 1 study evaluated AMG 232, an oral selective MDM2 inhibitor in patients with TP53 wild-type (P53WT), advanced solid tumors or multiple myeloma (MM). Methods In the dose escalation (n = 39), patients with P53WT refractory solid tumors enrolled to receive once-daily AMG 232 (15, 30, 60, 120, 240, 480, and 960 mg) for seven days every 3 weeks (Q3W). In the dose expansion (n = 68), patients with MDM2-amplified (well-differentiated and de-differentiated liposarcomas [WDLPS and DDLPS], glioblastoma multiforme [GBM], or other solid tumors [OST]), MDM2-overexpressing ER+ breast cancer (BC), or MM received AMG 232 at the maximum tolerated dose (MTD). Safety, pharmacokinetics, pharmacodynamics, and efficacy were assessed. Results AMG 232 had acceptable safety up to up to 240 mg. Three patients had dose-limiting toxicities of thrombocytopenia (n = 2) and neutropenia (n = 1). Due to these and other delayed cytopenias, AMG 232 240 mg Q3W was determined as the highest tolerable dose assessed in the dose expansion. Adverse events were typically mild/moderate and included diarrhea, nausea, vomiting, fatigue, decreased appetite, and anemia. AMG 232 plasma concentrations increased dose proportionally. Increases in serum macrophage inhibitor cytokine-1 from baseline were generally dose dependent, indicating p53 pathway activation. Per local review, there were no responses. Stable disease (durability in months) was observed in patients with WDLPS (3.9), OST (3.3), DDLPS (2.0), GBM (1.8), and BC (1.4–2.0). Conclusions In patients with P53WT advanced solid tumors or MM, AMG 232 showed acceptable safety and dose-proportional pharmacokinetics, and stable disease was observed.

Dedifferentiated liposarcoma with a rare presentation of disseminated intraperitoneal sarcomatosis: A case report

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Dedifferentiated liposarcoma can present with disseminated intraperitoneal sarcomatosis.

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Fluorescence in situ hybridization for MDM2 gene amplification is diagnostically discriminative.

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Prognosis is poor and the benefit of chemotherapy remains uncertain.

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Novel targeted therapies involving MDM2 and CKD4 inhibitors may emerge as viable systemic therapy options.

Introduction

Dedifferentiated liposarcoma is rare and tends to present with discrete tumors in the retroperitoneum, limbs and trunk. Majority of cases arise de-novo as primary tumors, while a minority occur as recurrences of well-differentiated liposarcomas. There has been no previous report of dedifferentiated liposarcoma presenting as disseminated intraperitoneal sarcomatosis.

Presentation of case

This report describes a young Asian female with disseminated intraperitoneal sarcomatosis arising from de-novo dedifferentiated liposarcoma, and discusses the diagnostic challenges faced in this highly unusual disease presentation. Initial biopsy was unconclusive, and considerations included sclerosing mesenteritis or an inflammatory myofibroblastic tumor. Fluorescence in situ hybridization was subsequently performed and showed amplification of the MDM2 gene. A diagnosis of dedifferentiated liposarcoma was then made.

Discussion

This was an extremely unusual presentation of advanced dedifferentiated liposarcoma that was eventually diagnosed using fluorescence in situ hybridization. Prognosis is poor and the only viable treatment options was palliative chemotherapy.

Conclusion

The diagnosis of dedifferentiated liposarcoma should be considered early and surgery carried out when still feasible.

Animal models of well-differentiated/dedifferentiated liposarcoma: utility and limitations

Liposarcoma is a malignant neoplasm of fat tissue. Well-differentiated and dedifferentiated liposarcoma (WDL/DDL) represent the two most clinically observed histotypes occurring in middle-aged to older adults, particularly within the retroperitoneum or extremities. WDL/DDL are thought to represent the broad spectrum of one disease, as they are both associated with the amplification in the chromosomal 12q13-15 region that causes MDM2 and CDK4 overexpression, the most useful predictor for liposarcoma diagnosis. In comparison to WDL, DDL contains additional genetic abnormalities, principally coamplifications of 1p32 and 6q23, that increase recurrence and metastatic rate. In this review, we discuss the xenograft and transgenic animal models generated for studying progression of WDL/DDL, highlighting utilities and pitfalls in such approaches that can facilitate or impede the development of new therapies.

A Low-Grade Myxoid Liposarcoma Arising in a Deep-Seated Conventional Lipoma

Myxoid liposarcomas (MLS) are known to arise de novo and have not been shown to derive from previous benign lesions (lipomas), whereas lipomas occasionally harbor areas of other benign mesenchymal tissue. Rarely, tumors presenting with MLS or round cell liposarcomas together with conventional liposarcoma have been classified as mixed liposarcomas. However, no case of MLS arising in a conventional lipoma has been described. In this article, we report a case of a young male presenting with a deep-seated soft tissue tumor of the posterior part of the thigh. The tumor was removed en bloc. Grossing revealed a small encapsulated myxoid lesion (2.5 cm) within the larger lipomatous tumor (14 cm). Histological examination and cytogenetic analysis revealed a FUS-CHOP positive low-grade MLS arising in a conventional lipoma without histological atypia, FUS-CHOP fusion, or CDK4/MDM2 amplification. While we cannot conclude whether these were collision tumors or an MLS progression from a lipoma, this case highlights the value of careful grossing in the soft tissue setting.

Practical Application of Cytology and Core Biopsy in the Diagnosis of Mesenchymal Tumors

Soft tissue neoplasms are increasingly being sampled by core needle biopsy and fine-needle aspiration (FNA), and these small biopsy specimens pose unique diagnostic challenges. Many advances in ancillary testing enable detection of characteristic immunophenotypes and molecular alterations, allowing accurate classification of soft tissue tumors in these small biopsy samples. This review outlines pattern-based diagnostic approaches to core biopsies and FNAs of soft tissue neoplasms, including formulation of practical differential diagnoses and relevant application of ancillary tests.

Pleomorphic Sarcomas: The State of the Art

This article focuses on pleomorphic sarcomas, which are malignant mesenchymal tumors with complex genetic background at the root of their morphologic pleomorphism. They are poorly differentiated tumors that may retain different lines of differentiation, sometimes correlating with clinicopathological or prognostic features. Accurate diagnosis in this group of tumors relies on adequate sampling due to their heterogeneity and assessment with both microscopy and large panels of immunohistochemistry. Molecular analyses have a limited role in their diagnosis as opposed to translocation-related sarcomas but may provide theranostic and important prognostic information in the future.

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.

Well-differentiated liposarcoma and dedifferentiated liposarcoma: An updated review

Well-differentiated liposarcoma (WDL)/atypical lipomatous tumor and dedifferentiated liposarcoma (DDL) together comprise the largest subgroup of liposarcomas, and constitute a histologic and behavioral spectrum of one disease. WDL and DDL typically occur in middle-aged to older adults, particularly within the retroperitoneum or extremities. WDL closely resembles mature adipose tissue, but typically shows fibrous septation with variable nuclear atypia and enlargement. WDL does not metastasize, but can dedifferentiate to DDL, which is associated with more aggressive clinical behavior, with a greater propensity for local recurrence and the capacity for metastasis. Although distant metastasis is rarer in DDL compared with other pleomorphic sarcomas, behavior is related to location, with a significantly worse outcome in retroperitoneal tumors. DDL typically has the appearance of undifferentiated pleomorphic or spindle cell sarcoma, and is usually a non-lipogenic sarcoma that is adjacent to WDL, occurs as a recurrence of WDL or which can arise de novo. WDL and DDL share similar background genetic aberrations; both are associated with high-level amplifications in the chromosomal 12q13-15 region, which includes the CDK4 and MDM2 cell cycle oncogenes. In addition, DDL harbor further genetic changes, particularly 6q23 and 1p32 coamplifications. While surgical excision remains the treatment mainstay with limited medical options for patients with aggressive recurrent disease or metastases, novel targeted therapies towards the gene products of chromosome 12 are being evaluated. This review summarizes the pathology of WDL and DDL, discussing morphology, immunohistochemistry, genetics and the differential diagnosis.

Molecular updates in adipocytic neoplasms✰

Adipocytic neoplasms include a diversity of both benign tumors (lipomas) and malignancies (liposarcomas), and each tumor type is characterized by its own unique molecular alterations driving tumorigenesis. Work over the past 30 years has established the diagnostic utility of several of these characteristic molecular alterations (e.g. MDM2 amplification in well- and dedifferentiated liposarcoma, FUS/EWSR1-DDIT3 gene fusions in myxoid liposarcoma, RB1 loss in spindle cell/pleomorphic lipoma). More recent studies have focused on additional molecular alterations which may have therapeutic or prognostic impact. This review will summarize several of the important molecular findings in adipocytic tumors that have been described over the past 10 years.

Machine learning analysis of gene expression data reveals novel diagnostic and prognostic biomarkers and identifies therapeutic targets for soft tissue sarcomas

Based on morphology it is often challenging to distinguish between the many different soft tissue sarcoma subtypes. Moreover, outcome of disease is highly variable even between patients with the same disease. Machine learning on transcriptome sequencing data could be a valuable new tool to understand differences between and within entities. Here we used machine learning analysis to identify novel diagnostic and prognostic markers and therapeutic targets for soft tissue sarcomas. Gene expression data was used from the Cancer Genome Atlas, the Genotype-Tissue Expression project and the French Sarcoma Group. We identified three groups of tumors that overlap in their molecular profiles as seen with unsupervised t-Distributed Stochastic Neighbor Embedding clustering and a deep neural network. The three groups corresponded to subtypes that are morphologically overlapping. Using a random forest algorithm, we identified novel diagnostic markers for soft tissue sarcoma that distinguished between synovial sarcoma and MPNST, and that we validated using qRT-PCR in an independent series. Next, we identified prognostic genes that are strong predictors of disease outcome when used in a k-nearest neighbor algorithm. The prognostic genes were further validated in expression data from the French Sarcoma Group. One of these, HMMR, was validated in an independent series of leiomyosarcomas using immunohistochemistry on tissue micro array as a prognostic gene for disease-free interval. Furthermore, reconstruction of regulatory networks combined with data from the Connectivity Map showed, amongst others, that HDAC inhibitors could be a potential effective therapy for multiple soft tissue sarcoma subtypes. A viability assay with two HDAC inhibitors confirmed that both leiomyosarcoma and synovial sarcoma are sensitive to HDAC inhibition. In this study we identified novel diagnostic markers, prognostic markers and therapeutic leads from multiple soft tissue sarcoma gene expression datasets. Thus, machine learning algorithms are powerful new tools to improve our understanding of rare tumor entities.

Soft-tissue sarcomas are a group of rare cancers that can be challenging to diagnose and treat. The morphology of the different soft-tissue sarcoma subtypes can overlap and the prognosis differs significantly between, and also within, the different subtypes. Moreover, targeted therapies are often not available. In this study we used transcriptome sequencing data from The Cancer Genome Atlas, containing 206 soft-tissue sarcoma samples which we analyzed using different machine learning algorithms to gain novel insights. When possible, we verified our findings in independent datasets or in cell lines. First, we found that both synovial sarcomas and malignant peripheral nerve sheath tumors show the largest overlap with normal tissue derived from the nervous system. This link with neural differentiation for synovial sarcoma was not well established until now. Second, genes were identified whose expression could be used to differentiate between the different soft-tissue sarcomas where the morphology overlaps. Third, novel prognostic genes were identified for separate subtypes. One gene, HMMR, which we found as a strong prognostic gene for leiomyosarcoma, was verified with immunohistochemistry on samples from our archives. Last, using a network analysis new potential therapies were identified. HDAC inhibitors were identified as a potential strong therapy for sarcomas, including leiomyosarcomas, which we verified in cell lines.

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.

Primary Breast Atypical Lipomatous Tumor/ Well-Differentiated Liposarcoma and Dedifferentiated Liposarcoma

Atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL) and its higher-grade counterpart, dedifferentiated liposarcoma (DDL), are extraordinarily rare tumors in the breast. The main differential diagnostic consideration of primary breast ALT/WDL is malignant phyllodes tumor with liposarcomatous differentiation, and the main differential diagnostic consideration of DDL in the breast is metaplastic breast carcinoma, particularly the spindle cell type, with heterologous sarcomatous differentiation. These differential diagnoses may be particularly challenging when evaluating limited core needle biopsy sampling. MDM2 and/or CDK4 protein overexpression and gene amplification are beneficial ancillary studies that can help establish the diagnosis of primary breast ALT/WDL and DDL, and effectively rule out the diagnoses of malignant phyllodes tumor and metaplastic breast carcinoma.

Pleural dedifferentiated liposarcoma: A case report

The present case report describes a rare case of pleural liposarcoma. A 45-year-old Japanese man was hospitalized for increasing left chest pain. Imaging revealed a 10-cm pleural tumor and a 1.7-cm contralateral right pulmonary nodule. Biopsy specimens of the pleural tumor showed undifferentiated spindle-shaped and/or rounded sarcomatous features with myxoid stroma. The patient underwent embolization of the arteries feeding the left pleural tumor and palliative partial resection of the pleural tumor. The surgically removed specimens exhibited similar undifferentiated sarcomatous features. The left pleural tumor regrew aggressively, and the patient succumbed to mortality ~4.2 months following hospitalization. Autopsy demonstrated a 35-cm left pleural tumor, metastasizing to both adrenal glands and lumbar vertebral bones, and a 2.2-cm primary adenocarcinoma of the right lung. The majority of the left pleural tumor and its metastases consisted of undifferentiated sarcomatous elements, however, scattered or aggregated lipoblasts were identified in localized areas adjacent to the diaphragm. Immunohistochemically, these lipoblasts were diffusely positive for MDM2 and focally positive for S-100 protein. Undifferentiated sarcomatous tumor cells were focally positive for MDM2 but negative for S-100 protein. This case was diagnosed as pleural dedifferentiated liposarcoma. The local aggressiveness of the pleural liposarcoma directly contributed to the patient's mortality. A review of the literature indicated that the dedifferentiated subtype may serve as a factor that is indicative of a poor prognosis for pleural liposarcoma.

A Case of Retroperitoneal Liposarcoma Mimicking an Adrenocortical Carcinoma

An adrenal mass can be a diagnostic challenge as it is not easy to differentiate the adrenal glands from other adrenal pseudotumours with only radio-imaging. We report a 28-year-old patient who was diagnosed radiologically as an adrenal cortical carcinoma after he presented with abdominal pain and fullness. Biochemically, he demonstrated secondary hyperaldosteronism. Intra-operatively there was a huge mass, inferior to a normal right adrenal, which was histopathologically proven to be a dedifferentiated liposarcoma.

Limited biopsies of soft tissue tumors: the contemporary role of immunohistochemistry and molecular diagnostics

Diagnosing soft tissue tumors is challenging, even on ample incisional biopsies or resection specimens. There are more than 100 distinct types of soft tissue neoplasms, including more than 80 benign and intermediate mesenchymal tumors and around 40 soft tissue sarcomas. Accurate diagnosis relies first upon recognition of characteristic histologic and cytologic features, including architecture, stromal characteristics, vascular patterns, and dominant cytology; these features may not be represented or apparent in limited core needle biopsy or fine needle aspiration specimens. Once a differential diagnosis is established, application of immunohistochemistry and cytogenetic or molecular diagnostic assays (especially fluorescence in situ hybridization) is used in an attempt to reach a specific diagnosis. In recent years, the diagnostic armamentarium for soft tissue tumors has expanded dramatically, following the discovery of molecular alterations that underlie the pathogenesis of soft tissue tumors. These include new diagnostic immunohistochemical markers that serve as useful surrogates for molecular genetic alterations. Availability of such markers has improved our ability to render accurate and specific diagnoses based on limited biopsy samples. In this review, examples of recently developed markers for the diagnosis of selected soft tissue tumor types will be discussed, including solitary fibrous tumor (STAT6), malignant peripheral nerve sheath tumor (H3K27me3), epithelioid hemangioendothelioma (CAMTA1), dedifferentiated liposarcoma (MDM2), and CIC-DUX4 sarcoma (WT1 and ETV4).

Co-expression of MDM2 and CDK4 in transformed human mesenchymal stem cells causes high-grade sarcoma with a dedifferentiated liposarcoma-like morphology

Amplification and overexpression of MDM2 and CDK4 are well-known diagnostic criteria for well-differentiated liposarcoma (WDLPS)/dedifferentiated liposarcoma (DDLPS). Although it was reported that the depletion of MDM2 or CDK4 decreased proliferation in DDLPS cell lines, whether MDM2 and CDK4 induce WDLPS/DDLPS tumorigenesis remains unclear. We examined whether MDM2 and/or CDK4 cause WDLPS/DDLPS, using two types of transformed human bone marrow stem cells (BMSCs), 2H and 5H, with five oncogenic hits (overexpression of hTERT, TP53 degradation, RB inactivation, c-MYC stabilization, and overexpression of HRAS^v12). In vitro functional experiments revealed that the co-overexpression of MDM2 and CDK4 plays a key role in tumorigenesis by increasing cell growth and migration and inhibiting adipogenic differentiation potency when compared with the sole expression of MDM2 or CDK4. Using mouse xenograft models, we found that the co-overexpression of MDM2 and CDK4 in 5H cells with five additional oncogenic mutations can cause proliferative sarcoma with a DDLPS-like morphology in vivo. Our results suggest that the co-overexpression of MDM2 and CDK4, along with multiple genetic factors, increases the tendency for high-grade sarcoma with a DDLPS-like morphology in transformed human BMSCs by accelerating their growth and migration and blocking their adipogenic potential.

Mesenchymal Neoplasms of the Genitourinary System: A Selected Review with Recent Advances in Clinical, Diagnostic, and Molecular Findings

Mesenchymal neoplasms of the genitourinary (GU) tract often pose considerable diagnostic challenges due to their wide morphologic spectrum, relative rarity, and unexpected incidence at GU sites. Soft tissue tumors arise throughout the GU tract, whether from adventitia surrounding or connective tissues within the kidneys, urinary bladder, and male and female genital organs. This selected article focuses on a subset of these lesions, ranging from benign to malignant and encompassing a range of patterns of mesenchymal differentiation, where recent scholarship has lent greater insight into their clinical, molecular, or diagnostic features.

Lipomatous Soft-tissue Tumors

Lipomatous soft-tissue tumors are the most common neoplasms encountered by physicians. They range from benign lipomas to high-grade liposarcomas. Unplanned excisions of sarcomas are commonly due to the presumptive diagnosis of lipoma and can be avoided by understanding their diagnostic magnetic resonance imaging appearance. Magnetic resonance images should be obtained for all soft-tissue masses that are deep to fascia or those >5 cm in subcutaneous tissue. Atypical lipomatous tumors present as large deep fatty masses and have a propensity for local recurrence and a small risk of malignant transformation. Well-differentiated liposarcomas are histologically identical to atypical lipomatous tumors but have a markedly worse prognosis secondary to their anatomic location. Masses that lack isointense signal to subcutaneous fat on MRI may represent a sarcoma and require a biopsy before definitive treatment. Large deep lipomatous masses and liposarcomas should be sent to a sarcoma referral center for definitive treatment.

Metabolic targeting with recombinant methioninase combined with palbociclib regresses a doxorubicin-resistant dedifferentiated liposarcoma

Liposarcoma is the most common type of soft tissue sarcoma. Among the subtypes of liposarcoma, dedifferentiated liposarcoma (DDLPS) is recalcitrant and has the lowest survival rate. The aim of the present study is to determine the efficacy of metabolic targeting with recombinant methioninase (rMETase) combined with palbociclib (PAL) against a doxorubicin (DOX)-resistant DDLPS in a patient-derived orthotopic xenograft (PDOX) model. A resected tumor from a patient with recurrent high-grade DDLPS in the right retroperitoneum was grown orthotopically in the right retroperitoneum of nude mice to establish a PDOX model. The PDOX models were randomized into the following groups when tumor volume reached 100 mm³: G1, control without treatment; G2, DOX; G3, PAL; G4, recombinant methioninase (rMETase); G5, PAL combined with rMETase. Tumor length and width were measured both pre- and post-treatment. On day 14 after initiation, all treatments significantly inhibited tumor growth compared to the untreated control except DOX. PAL combined with rMETase was significantly more effective than both DOX, rMETase alone, and PAL alone. Combining PAL and rMETase significantly regressed tumor volume on day 14 after initiation of treatment and was the only treatment to do so. The relative body weight on day 14 compared with day 0 did not significantly differ between each treatment group. The results of the present study indicate the powerful combination of rMETase and PAL should be tested clinically against DDLPS in the near future.

Primary small bowel mesentery de-differentiated liposarcoma causing torsion with no recurrence for 5 years: A case report and review of the literature

RATIONALE

Liposarcoma (LPS) is a rare malignant soft-tissue tumor. Management of LPS is relatively difficult, because there are no characteristic symptoms, or biomarkers, nor any established effective treatment. Hence, the report of the accumulation of each LPS case is necessary. We experienced an extremely rare case of torsion caused by a primary small bowel mesentery LPS.

PATIENT'S CONCERN

A 70-year-old male consulted our hospital with the complaints of abdominal pain and sudden vomiting.

DIAGNOSIS

No lump could be palpated, and tumor markers tested were within normal limits. However, computed tomography revealed an intestinal obstruction caused by torsion of the small bowel due to an LPS tumor.

INTERVENTIONS

After decompression of the intestinal obstruction by use of an ileus tube, surgical treatment was performed with rapidity.

OUTCOME

The torsion was found to be caused by the tumor that originated from the small bowel mesentery. The tumor was resected along with a portion of the small bowel. The growth of adipose tissues of various sizes and containing atypical cells was detected by histopathological examination. Also, immunohistochemical examination resulted in positive immuno-reactions for MDM2, CDK4, and p16INK4, which indicated the tumor to be a de-differentiated LPS. The patient was discharged on postoperative day 14 without any complications, and no recurrence of the tumor was observed at 5 years after the operation.

LESSONS

LPS should be considered in differential diagnosis of bowel torsion, and careful management is required because of the high possibility of recurrence. Patients should be followed carefully for at least 5 years, and further accumulation of data will be required in order to establish the appropriate management of LPS.

Subclassification of pleomorphic sarcomas: How and why should we care?

Pleomorphic sarcomas are a heterogeneous group of mesenchymal neoplasms with widely varied clinical behavior but overlapping histologic appearances. The following guidelines are helpful when approaching the diagnosis of a pleomorphic sarcoma. (1) Be aware of the relative incidence of the various sarcoma types: several pleomorphic sarcomas are relatively common (e.g., dedifferentiated liposarcoma and undifferentiated pleomorphic sarcoma), whereas others are exceptionally rare. (2) Pay attention to anatomic location: some pleomorphic sarcomas have a predilection for somatic soft tissues, especially the thigh (e.g., undifferentiated pleomorphic sarcoma, pleomorphic liposarcoma, pleomorphic rhabdomyosarcoma), whereas other pleomorphic sarcomas most often arise in the retroperitoneum (e.g., dedifferentiated liposarcoma). (3) Carefully sample the resection specimen, paying particular attention to areas with differences in gross appearances (e.g., fleshy, fibrous, mucoid, or gritty). (4) Search for histologic clues (i.e., myxoid stroma, lipoblasts, and osteoid matrix, in order to diagnose myxofibrosarcoma, pleomorphic liposarcoma, and extraskeletal osteosarcoma, respectively); these critical diagnostic features may be limited in extent. (5) Apply immunohistochemistry judiciously, after generating a differential diagnosis; always exclude metastatic sarcomatoid carcinoma and melanoma before diagnosing a pleomorphic sarcoma. This review will present an approach to the diagnosis of pleomorphic sarcomas, emphasizing differential diagnosis and the application of ancillary studies (immunohistochemistry and FISH), when relevant.

Protein Degradation and the Pathologic Basis of Disease

The abundance of any protein is determined by the balance of protein synthesis and protein degradation. Regulated protein degradation has emerged as a powerful means of precisely controlling individual protein abundance within cells and is largely mediated by the ubiquitin-proteasome system (UPS). By controlling the levels of key regulatory proteins, the UPS contributes to nearly every aspect of cellular function. The UPS also functions in protein quality control, rapidly identifying and destroying misfolded or otherwise aberrant proteins that may be toxic to cells. Increasingly, we understand that dysregulation of protein degradation pathways is critical for many human diseases. Conversely, the versatility and scope of the UPS provides opportunities for therapeutic intervention. In this review, we will discuss the basic mechanisms of protein degradation by the UPS. We will then consider some paradigms of human disease related to protein degradation using selected examples. Finally, we will highlight several established and emerging therapeutic strategies based on altering pathways of protein degradation.

[Left atrial intimal sarcoma: A rare cause of acute heart failure]

Primitive intimal sarcoma is a rare malignant cardiac tumor. Through the observation of a 41-year-old man who presented with an acute heart failure revealing a left atrial intimal sarcoma, we discuss different diagnostic and therapeutic modalities.