Atypical spindle cell lipoma: a clinicopathologic, immunohistochemical, and molecular study emphasizing its relationship to classical spindle cell lipoma

Intra-Abdominal and Retroperitoneal Benign Lipomatous Tumors-An Extremely Rare Mimic of Liposarcoma and its Diagnostic Challenge

Background. Lipomas are common superficial soft tissue tumors of mature adipocytes. In contrast, well-differentiated/dedifferentiated liposarcoma typically presents in the retroperitoneum as large masses. We provide clinicopathologic and follow-up details of 9 retroperitoneal/intra-abdominal benign lipomatous tumors (BLT) and discuss the utility of ancillary fluorescence in situ hybridization (FISH) in distinguishing from their malignant counterparts. Design. Clinicopathologic details and histology of 9 intra-abdominal and retroperitoneal lipomas were studied along with ancillary CD10 immunohistochemistry (IHC) and FISH for MDM2 and CDK4 amplification. Results. There were 6 females and 3 males. Median age at diagnosis was 52 years (range 36-81 years). Seven were identified incidentally and 2 presented with primary complaints. On imaging, 7 were considered suspicious for liposarcoma. Grossly, the tumors ranged from 3.4 to 41.2 cm (median 16.5 cm). Histologically, all cases showed well-differentiated BLT, further classified as lipoma (n = 7; 1 with metaplastic ossification, 2 with prominent vessels, and 4 ordinary lipomas) and lipoma-like hibernoma (n = 2)-the latter 2 showed intramuscular lesions with interspersed brown fat. CD10 IHC showed strong staining in the 2 hibernomas, whereas the staining was weak in the remaining. MDM2 and CDK4 amplification were negative by FISH in all. Follow-up (median 18 months) did not show recurrence on clinical or imaging evaluation. Conclusion. Retroperitoneal/intra-abdominal BLT are extremely rare and are indistinguishable clinically and radiographically from liposarcoma. This necessitates molecular confirmation even when the histology is convincingly benign, for a confident diagnosis. Our cohort shows that conservative excision without removal of abutted organs is sufficient in most cases.

Case report: Atypical spindle cell/pleomorphic lipomatous tumor masquerading as a myxoid liposarcoma or intramuscular myxoma

Atypical spindle cell/pleomorphic lipomatous tumors (ASPLTs) were recently categorized as benign lipomatous tumors. However, accurate and complete preoperative diagnosis of ASPLTs may be difficult. Furthermore, diagnosis based on magnetic resonance imaging (MRI) findings is uncertain because of the varying ratios of the fat component within the tumor. Here, we report a case of ASPLT masquerading as a myxoid tumor. Although MRI findings were consistent with a myxoid liposarcoma, needle biopsy findings suggested a myxoma, and we performed marginal resection. Histopathological findings revealed infiltrating spindle cells with atypia. In addition, immunohistochemistry (IHC) showed positive staining for CD34 and heterogeneous retinoblastoma deficiency, and fluorescence in situ hybridization (FISH) showed no amplification of mouse double minute 2 homolog and no rearrangement of FUS or EWSR1. When MRI and histopathological findings suggest a myxoid tumor, IHC and FISH should be considered and performed for a precise and accurate diagnosis.

Characterization of Aberrations in DNA Damage Repair Pathways in Gastrointestinal Stromal Tumors: The Clinicopathologic Relevance of γH2AX and 53BP1 in Correlation with Heterozygous Deletions of CHEK2, BRCA2, and RB1

Genetic aberrations involving DNA damage repair (DDR) remain underexplored in gastrointestinal stromal tumors (GISTs). We characterized DDR abnormalities using targeted next-generation sequencing and multiplex ligation-dependent probe amplification, and performed immunofluorescence (IF) and immunohistochemistry (IHC) analyses of γH2AX and 53BP1. Consistent with IF-validated nuclear co-localization, γH2AX and 53BP1 showed robust correlations in expression levels, as did both biomarkers between IF and IHC. Without recurrent pathogenic single-nucleotide variants, heterozygous deletions (HetDels) frequently targeted DNA damage-sensing genes, with CHEK2-HetDel being the most prevalent. Despite their chromosomal proximity, BRCA2 and RB1 were occasionally hit by HetDels and were seldom co-deleted. HetDels of CHEK2 and BRCA2 showed a preference for older age groups, while RB1-HetDel predominated in the non-gastric, high-risk, and 53BP1-overexpressing GISTs. Higher risk levels were consistently related to γ-H2AX or 53BP1 overexpression (all p < 0.01) in two validation cohorts, while only 53BP1 overexpression was associated with the deletion of KIT exon 11 (KITex11-del) among genotyped GISTs. Low expressers of dual biomarkers were shown by univariate analysis to have longer disease-free survival (p = 0.031). However, higher risk levels, epithelioid histology, and KITex11-del retained prognostic independence. Conclusively, IHC is a useful surrogate of laborious IF in the combined assessment of 53BP1 and γ-H2AX to identify potential DDR-defective GISTs, which were frequently aberrated by HetDels and a harbinger of progression.

Large retroperitoneal atypical spindle cell lipomatous tumor, an extremely rare neoplasm: A case report

BACKGROUND

Atypical spindle cell lipomatous tumor (ASLT) is a rare soft tissue neoplasm with a low potential for malignancy. ASLT frequently occurs in the limb and limb girdles. However, large retroperitoneal ASLTs are extremely rare. There was no concrete case report of retroperitoneal ASLTs.

CASE SUMMARY

An 18-year-old woman presented with abdominal pain and a palpable mass. Abdominal computed tomography revealed a large fatty mass that was approximately 30 cm in size and filled the entire abdominal cavity. Surgical excision was indicated. The tumor did not invade the adjacent organs. The pelvic cavity was then too narrow to dissect smoothly. The mass was successfully excised without tumor rupture or adjacent organ injury. Microscopically, the neoplasm was a well-differentiated adipocytic neoplasm. Immunohistochemical staining showed that the spindle cells were positive for CD34 and desmin, in addition to multifocal positivity for S100 protein. These histological features were consistent with an ASLT. The patient's postoperative course was uneventful. At the 12-mo follow-up, no evidence of recurrence or metastasis was observed.

CONCLUSION

To the best of our knowledge, our study is the first concrete report of a large retroperitoneal ASLT in the English literature. In the large retroperitoneal ASLT located in the pelvic cavity, which made it too narrow and tight to dissect, complete excision is difficult but very important because of recurrence risk. Although large retroperitoneal ASLTs are considered extremely rare, their detection is important for accurate evaluation and management. Owing to their significant rarity, retrospective multicenter case studies are required to determine the clinicopathologic characteristics.

An Atypical Pleomorphic Lipomatous Tumor Presenting As Groin Mass

Cutaneous tumors with adipocyte differentiation are frequently excised by surgeons in their daily clinical practice and sometimes less common histological diagnoses arise. Knowledge of different pathological entities and their natural history is essential for better patient management.

Atypical spindle cell/Pleomorphic lipomatous tumor (ASPLT) is a recent group included in the WHO classification. We report a case of a middle-aged man with an atypical pleomorphic lipomatous tumor in an unusual location.

The role of the integral type II transmembrane protein BRI2 in health and disease

BRI2 is a type II transmembrane protein ubiquitously expressed whose physiological function remains poorly understood. Although several recent important advances have substantially impacted on our understanding of BRI2 biology and function, providing valuable information for further studies on BRI2. These findings have contributed to a better understanding of BRI2 biology and the underlying signaling pathways involved. In turn, these might provide novel insights with respect to neurodegeneration processes inherent to BRI2-related pathologies, namely Familial British and Danish dementias, Alzheimer's disease, ITM2B-related retinal dystrophy, and multiple sclerosis. In this review, we provided a state-of-the-art outline of BRI2 biology, both in physiological and pathological conditions, and discuss the proposed molecular underlying mechanisms. Overall, the BRI2 knowledge here reviewed is of extreme importance and may contribute to propose BRI2 and/or BRI2 proteolytic fragments as novel therapeutic targets for neurodegenerative diseases, such as Alzheimer's disease.

Myxoid pleomorphic liposarcoma-a clinicopathologic, immunohistochemical, molecular genetic and epigenetic study of 12 cases, suggesting a possible relationship with conventional pleomorphic liposarcoma

Myxoid pleomorphic liposarcoma is a recently defined subtype of liposarcoma, which preferentially involves the mediastinum of young patients and shows mixed histological features of conventional myxoid liposarcoma and pleomorphic liposarcoma. While myxoid pleomorphic liposarcoma is known to lack the EWSR1/FUS-DDIT3 fusions characteristic of the former, additional genetic data are limited. To further understand this tumor type, we extensively examined a series of myxoid pleomorphic liposarcomas by fluorescence in situ hybridization (FISH), shallow whole genome sequencing (sWGS) and genome-wide DNA methylation profiling. The 12 tumors occurred in 6 females and 6 males, ranging from 17 to 58 years of age (mean 33 years, median 35 years), and were located in the mediastinum (n = 5), back, neck, cheek and leg, including thigh. Histologically, all cases consisted of relatively, bland, abundantly myxoid areas with a prominent capillary vasculature, admixed with much more cellular and less myxoid foci containing markedly pleomorphic spindled cells, numerous pleomorphic lipoblasts and elevated mitotic activity. Using sWGS, myxoid pleomorphic liposarcomas were found to have complex chromosomal alterations, including recurrent large chromosomal gains involving chromosomes 1, 6-8, 18-21 and losses involving chromosomes 13, 16 and 17. Losses in chromosome 13, in particular loss in 13q14 (including RB1, RCTB2, DLEU1, and ITM2B genes), were observed in 4 out of 8 cases analyzed. Additional FISH analyses confirmed the presence of a monoallelic RB1 deletion in 8/12 cases. Moreover, nuclear Rb expression was deficient in all studied cases. None showed DDIT3 gene rearrangement or MDM2 gene amplification. Using genome-wide DNA methylation profiling, myxoid pleomorphic liposarcomas and conventional pleomorphic liposarcomas formed a common methylation cluster, which segregated from conventional myxoid liposarcomas. While the morphologic, genetic and epigenetic characteristics of myxoid pleomorphic liposarcoma suggest a link with conventional pleomorphic liposarcoma, its distinctive clinical features support continued separate classification for the time being.

The Rapidly Expanding Group of RB1-Deleted Soft Tissue Tumors: An Updated Review

The classification of soft tissue tumors has evolved considerably in the last decade, largely due to advances in understanding the pathogenetic basis of many of these, sometimes rare, tumors. Deletion of Retinoblastoma 1 (RB1), a well-known tumor suppressor gene, has been implicated in the tumorigenesis of a particular group of soft tissue neoplasms. This group of so-called “RB1-deleted soft tissue tumors” has been rapidly expanding in recent years, currently consisting of spindle cell/pleomorphic lipoma, atypical spindle cell/pleomorphic lipomatous tumor, pleomorphic liposarcoma, myofibroblastoma, cellular angiofibroma, and acral fibromyxoma. Most of these neoplasms, except pleomorphic liposarcoma, are considered benign entities and are mainly described in the older adult population. This article will review the currently known morphological, immunohistochemical, and molecular features of this heterogeneous group of mesenchymal tumors with an emphasis on differential diagnosis.

A Case Report of Atypical Spindle Cell Lipomatous Tumor of the Tongue

Herein, we report a case of atypical spindle cell lipomatous tumor (ASCLT) on both sides of the tongue in a 74-year-old male patient. The patient was referred to our department for treatment of the masses in the tongue. Several elastic soft indolent masses were detected during the first examination. The masses were well defined, and their consistency was similar to that of adipose tissues. No signs of induration were observed in the surrounding tissues. The patient was not aware of the masses, which were only detected during his visit at the dental clinic that referred him to our institution. Thus, the onset of the masses remains unknown. ASCLT was identified via histopathological examination. Then, tumor excision was performed under general anesthesia. Thirteen months after surgery, the condition of the patient was good, and signs of local recurrence or postoperative metastasis were not observed.

Atypical spindle cell/pleomorphic lipomatous tumor

Atypical spindle cell/pleomorphic lipomatous tumor (ASPLT) is a recently described morphologically low-grade and clinically indolent adipocytic tumor, which will be incorporated as a new tumor entity in the upcoming 5th edition of the WHO Classification of Soft tissue and Bone tumors. Histologically, ASPLTs are characterized by ill-defined tumor margins and the presence of variable proportions of mild-to-moderately atypical spindle cells, adipocytes, lipoblasts, pleomorphic multinucleated cells and a myxoid or collagenous extracellular matrix. ASPLTs can show a wide variety of microscopic appearances and there is histologic overlap with diverse mimics. The diagnosis of ASPLT can therefore be challenging. Molecular studies have shown a consistent absence of MDM2 or CDK4 amplification. On the other hand, deletions or losses of 13q14, including RB1, have been identified in a significant subset of cases. This review provides an overview of the currently known clinical and pathological features of ASPLTs, detailing its most relevant differential diagnoses.

First Glance of Molecular Profile of Atypical Cellular Angiofibroma/Cellular Angiofibroma with Sarcomatous Transformation by Next Generation Sequencing

Cellular angiofibroma is a rare benign mesenchymal neoplasm most commonly occurring in the vulvovaginal region in women and the inguinoscrotal region in men with specific genetic deletion involved in the RB1 gene in chromosome 13q14 region. Atypical cellular angiofibroma and cellular angiofibroma with sarcomatous transformation are recently described variants showing worrisome morphological features and strong, diffuse p16 expression. Nevertheless, the molecular profile of these tumor entities is largely unknown. We carried out a next generation sequencing (NGS) study from six cases of atypical cellular angiofibroma and cellular angiofibroma with sarcomatous transformation. We were able to identify oncogenic TP53 gene mutations (33%) which may contribute to pathogenesis also resulting in p16 overexpression. In addition, RB1 gene alterations generally present were identified. Since it is a recently described and rare entity, the whole molecular signaling pathway is still largely obscured and the analysis of larger cohorts is needed to elucidate this issue.

What's new in adipocytic neoplasia?

Adipocytic tumors are frequently encountered in routine practice, and while the vast majority represent commonly encountered tumor types (e.g., benign lipoma), the heterogeneity and rarity of other adipocytic neoplasms can pose diagnostic challenges. Atypical and malignant adipocytic tumors account for approximately 20% of all sarcomas. The 2013 World Health Organization (WHO) classification of soft tissue and bone tumors recognizes four major liposarcoma subtypes, characterized by distinct clinical behavior, distinctive morphologies, as well as unique genetic findings: atypical lipomatous tumor/well-differentiated liposarcoma, dedifferentiated liposarcoma, myxoid liposarcoma, and pleomorphic liposarcoma. Since the publication of the 2013 WHO classification of soft tissue and bone tumors, the most notable change in the category of adipocytic tumors has been made in the clinicopathologic and molecular characterization of the heterogeneous but distinct group of "atypical low-grade adipocytic neoplasms with spindle cell features," for which the term atypical spindle cell/pleomorphic lipomatous tumor has been proposed. Another substantive change in the group of adipocytic tumors is the introduction of pleomorphic myxoid liposarcoma (myxoid pleomorphic liposarcoma) as an apparently novel subtype of aggressive liposarcoma, especially occurring in children and young adults with a predilection for the mediastinum. This review will further focus upon the diagnostic criteria of these novel emerging entities in the group of adipocytic tumors.

[Tumors with predominantly adipocytic morphology]

More than 20% of soft-tissue tumors belong to the group of adipocytic neoplasms. Difficulties may occur in the differential diagnosis of lipomas versus atypical lipomatous tumors/well-differentiated liposarcomas, in the distinction of dedifferentiated liposarcomas from other soft-tissue sarcoma entities and in the detailed subtyping of liposarcomas. Especially in biopsies, the correct diagnosis and grading may be hampered due to limited tissue. Because of the ever-increasing molecular-pathological knowledge of soft-tissue tumors and the rising distribution of molecular diagnostic assays in institutes of pathology, differential diagnosis has been facilitated, as more than 90% of adipocytic tumors carry more or less specific genomic alterations. In the following, the most important subtypes of adipocytic tumors are described morphologically and genomically.

Diagnostic Immunohistochemistry for Soft Tissue and Bone Tumors: An Update

Although some soft tissue and bone tumors can be identified based on histologic features alone, immunohistochemistry plays a critical diagnostic role for most mesenchymal tumor types. The discovery of recurrent genomic alterations in many benign and malignant mesenchymal neoplasms has added important biologic insights and expanded the spectrum of some diagnostic subgroups. Some tumors are defined by unique genomic alterations, whereas others share abnormalities that are not tumor-specific and can be observed in a sometimes broad range of biologically unrelated neoplasms. We herein focus on novel immunohistochemical markers, based on molecular genetic alterations, which are particularly useful in the diagnostic workup of selected groups of soft tissue and bone tumors, including recently described entities, specifically round cell sarcomas (Ewing sarcoma, CIC-rearranged sarcoma, and BCOR-rearranged sarcoma), vascular tumors (epithelioid hemangioma, epithelioid hemangioendothelioma, and pseudomyogenic hemangioendothelioma), SMARCB1-deficient neoplasms, adipocytic tumors (spindle cell/pleomorphic lipoma, atypical spindle cell lipomatous tumor, and conventional atypical lipomatous tumor), giant cell-rich bone tumors (giant cell tumor of bone and chondroblastoma), and biphenotypic sinonasal sarcoma. Given the complex nature of sarcoma classification, and the rarity of many mesenchymal tumor types, careful integration of clinical presentation, imaging features, histology, immunophenotype, and cytogenetic/molecular alterations is crucial for accurate diagnosis of soft tissue and bone tumors.

Quantitative Analysis of Seven New Prostate Cancer Biomarkers and the Potential Future of the 'Biomarker Laboratory'

Prostate cancer is the third highest cause of male mortality in the developed world, with the burden of the disease increasing dramatically with demographic change. There are significant limitations to the current diagnostic regimens and no established effective screening modality. To this end, research has discovered hundreds of potential ‘biomarkers’ that may one day be of use in screening, diagnosis or prognostication. However, the barriers to bringing biomarkers to clinical evaluation and eventually into clinical usage have yet to be realised. This is an operational challenge that requires some new thinking and development of paradigms to increase the efficiency of the laboratory process and add ‘value’ to the clinician. Value comes in various forms, whether it be a process that is seamlessly integrated into the hospital laboratory environment or one that can provide additional ‘information’ for the clinical pathologist in terms of risk profiling. We describe, herein, an efficient and tissue-conserving pipeline that uses Tissue Microarrays in a semi-automated process that could, one day, be integrated into the hospital laboratory domain, using seven putative prostate cancer biomarkers for illustration.

Validation of Osteogenic Properties of Cytochalasin D by High-Resolution RNA-Sequencing in Mesenchymal Stem Cells Derived from Bone Marrow and Adipose Tissues

Differentiation of mesenchymal stromal/stem cells (MSCs) involves a series of molecular signals and gene transcription events required for attaining cell lineage commitment. Modulation of the actin cytoskeleton using cytochalasin D (CytoD) drives osteogenesis at early timepoints in bone marrow-derived MSCs and also initiates a robust osteogenic differentiation program in adipose tissue-derived MSCs. To understand the molecular basis for these pronounced effects on osteogenic differentiation, we investigated global changes in gene expression in CytoD-treated murine and human MSCs by high-resolution RNA-sequencing (RNA-seq) analysis. A three-way bioinformatic comparison between human adipose tissue-derived MSCs (hAMSCs), human bone marrow-derived MSCs (hBMSCs), and mouse bone marrow-derived MSCs (mBMSCs) revealed significant upregulation of genes linked to extracellular matrix organization, cell adhesion and bone metabolism. As anticipated, the activation of these differentiation-related genes is accompanied by a downregulation of nuclear and cell cycle-related genes presumably reflecting cytostatic effects of CytoD. We also identified eight novel CytoD activated genes-VGLL4, ARHGAP24, KLHL24, RCBTB2, BDH2, SCARF2, ACAD10, HEPH-which are commonly upregulated across the two species and tissue sources of our MSC samples. We selected the Hippo pathway-related VGLL4 gene, which encodes the transcriptional co-factor Vestigial-like 4, for further study because this pathway is linked to osteogenesis. VGLL4 small interfering RNA depletion reduces mineralization of hAMSCs during CytoD-induced osteogenic differentiation. Together, our RNA-seq analyses suggest that while the stimulatory effects of CytoD on osteogenesis are pleiotropic and depend on the biological state of the cell type, a small group of genes including VGLL4 may contribute to MSC commitment toward the bone lineage.

DLEU1 contributes to ovarian carcinoma tumourigenesis and development by interacting with miR-490-3p and altering CDK1 expression

Recently, a large number of studies have focused on the important role of long non-coding RNAs (lncRNAs) in metabolism and development and have found that abnormal lncRNA expression is associated with the pathogenesis and development of many diseases. The lncRNA DLEU1 is involved in many solid tumours and haematological malignancies. However, its role in epithelial ovarian carcinoma (EOC) and the associated molecular mechanisms has not been reported. In this study, quantitative reverse transcription-PCR (qRT-PCR) demonstrated higher lncRNADLEU1 expression in EOC tissues than in normal tissues. Plasmid transfection of DLEU1 to up-regulate its expression in the ovarian cancer cell lines A2780 and OVCAR3 increased cell proliferation, migration, and invasion, while inhibited apoptosis. Nude mouse xenograft assay demonstrated that DLEU1 overexpression promoted tumour growth in vivo. QRT-PCR showed decreased miR-490-3p expression, while Western blotting demonstrated increased its target genes CDK1, cyclinD1 and SMARCD1, as well as matrix metalloproteinase-2 (MMP2), Bcl-xL and P70S6K protein expression, respectively. Short interfering RNA silencing of DLEU1 produced opposite results, where qRT-PCR showed increased miR-490-3p expression. The dual-luciferase reporter assay revealed a direct interaction between DLEU1 and miR-490-3p. MiR-490-3p plays a tumour suppressor role in epithelial ovarian cancer by targeting CDK1 regulation and influencing SMARCD1 and cyclin D1 (CCND1) expressions. Therefore, we suggest that through interaction with miR-490-3p, DLEU1 may influence the expression of CDK1, CCND1 and SMARCD1 protein, subsequently promoting the development and progression of EOC.

CRISPR/Cas9 mediated knockout of rb1 and rbl1 leads to rapid and penetrant retinoblastoma development in Xenopus tropicalis

Retinoblastoma is a pediatric eye tumor in which bi-allelic inactivation of the Retinoblastoma 1 (RB1) gene is the initiating genetic lesion. Although recently curative rates of retinoblastoma have increased, there are at this time no molecular targeted therapies available. This is, in part, due to the lack of highly penetrant and rapid retinoblastoma animal models that facilitate rapid identification of targets that allow therapeutic intervention. Different mouse models are available, all based on genetic deactivation of both Rb1 and Retinoblastoma-like 1 (Rbl1), and each showing different kinetics of retinoblastoma development. Here, we show by CRISPR/Cas9 techniques that similar to the mouse, neither rb1 nor rbl1 single mosaic mutant Xenopus tropicalis develop tumors, whereas rb1/rbl1 double mosaic mutant tadpoles rapidly develop retinoblastoma. Moreover, occasionally presence of pinealoblastoma (trilateral retinoblastoma) was detected. We thus present the first CRISPR/Cas9 mediated cancer model in Xenopus tropicalis and the first genuine genetic non-mammalian retinoblastoma model. The rapid kinetics of our model paves the way for use as a pre-clinical model. Additionally, this retinoblastoma model provides unique possibilities for fast elucidation of novel drug targets by triple multiplex CRISPR/Cas9 gRNA injections (rb1 + rbl1 + modifier gene) in order to address the clinically unmet need of targeted retinoblastoma therapy.

Spindle Cell Lipoma Occurring in the Buccal Mucosa: An Unusual Location of This Benign Lipomatous Neoplasm

Spindle cell lipoma is a benign lipomatous neoplasm, which rarely occurs in the oral cavity. The aims of this paper are to report a case of spindle cell lipoma located in buccal mucosa and discuss the main clinical, histological, and immunohistochemical findings of this entity. Thus, we report a 4-year history of an asymptomatic smooth surface nodule in an elderly Caucasian man with clinical hypothesis of fibroma. The histopathological examination showed spindle cells, mature adipose tissue, and many mast cells in a stroma of connective tissue presenting ropey collagen fibers bundles. After immunohistochemical analysis, the final diagnosis was spindle cell lipoma.

[Value of core needle biopsy in preoperative diagnostics of soft tissue tumors: possibilities and limitations]

The differential diagnosis of soft tissue swellings encompasses a variety of benign, intermediate, low-grade malignant and high-grade neoplastic lesions in addition to tumor-like reactive processes. As treatment of these heterogeneous conditions varies greatly from conservative observation and simple local excision up to extensive radical surgical resection, treatment decisions are based mainly on a precise preoperative histological diagnosis on limited biopsy material. Even for clinically unequivocal sarcomas, the importance of the preoperative histological diagnosis has been increasingly emphasized as different therapeutic regimens have been established for different sarcoma types and the indications for preoperative treatment is influenced by the tumor grade and by the entity itself. Other factors positively influencing the increasing use of core needle biopsy for preoperative tumor diagnosis in soft tissue pathology are the availability of modern high-resolution imaging modalities as well as the establishment of several new second generation immunohistochemical markers and the discovery of entity-specific translocations detected by fluorescence in situ hybridization (FISH) in several sarcoma subtypes. In this review it will be shown that a targeted approach for processing core needle biopsies oriented towards the characteristic topographical, demographic, cytomorphological and architectural features of soft tissue lesions facilitates a precise diagnosis of soft tissue neoplasms in most cases. However, profound knowledge of the different aspects of soft tissue tumor diagnostics and familiarity with the frequent as well as the less common and rare tumor entities and variants is a prerequisite for appropriate interpretation of core needle biopsy findings and for selecting a limited but well-suited marker panel. The utilization of modern immunohistochemistry and/or FISH methods is highly useful for establishing the diagnosis of rare and unusual neoplasms in core needle biopsies.