Classification Of Soft Tissue Tumors Research Articles

Tumor vulvar similar a lipoblastoma: descripción de un nuevo caso y revisión de la literatura

Lipoblastoma-like tumor of the vulva (LBLTV) was first described as a benign mesenchymal neoplasia; it was not recognized as a separate diagnosis in the 2013 WHO classification of soft-tissue tumors. To date, only 19 cases have been reported. LBLTV differential diagnosis includes other tumors of the vulvoperineal region and tumors with adipocytic differentiation, most of which are benign and thus a misdiagnosis has few clinical consequences. However, LBLTV may also mimic some aggressive lipomatous neoplasms. We describe a case of LBLTV in a 28 year-old woman and review the literature.

Orbital hybrid peripheral nerve sheath tumors.

Hybrid peripheral nerve sheath tumors (HPNST) are recently classified tumors from the World Health Organization Classification of soft tissue tumors that display combined features of more than one peripheral nerve sheath tumor. Acknowledgment is important because of its association with the development of neurofibromatosis type 1, type 2, and schwannomatosis. Orbital involvement is rare and only six cases of HPNST have been documented on literature. This article serves to review the pathophysiology, clinical manifestation, diagnosis, treatment, and prognosis of this infrequent but important orbital tumor.

Prevalence of Soft Tissue Tumours in Duhok-Iraq: A Practical Immunohistochemical Approach

Introduction: The field of Soft Tissue Tumours (STT) is enormously vast, and yet histologically and relatively vague. Although benign tumours are more common than malignant tumours, the relative rarity of sarcomas, little knowledge, and insufficient local studies, made the authors eager to search more through this field and explore the hidden and unobvious features of these tumours in our locality. Aim: The study aimed to apply traditional and updated antibodies to characterise STT in Duhok-Iraq, morphologically and immunohistochemically. Materials and Methods: In this cross-sectional study, 886 STT were received in the Department of Histopathology in Central General Laboratories and Vin Private Laboratories, Duhok-Iraq, over a period of 11 consecutive years (January, 2009 to December, 2019). Cases were studied clinically and then, morphologically categorised. Immunohistochemical workup was performed when needed, to sub-classify undifferentiated tumours. Results: Benign tumours (n=768) ovarian sarcomas (n=118) by a ratio of 6.5:1, both showed a wide age range (1 month to 82 years), with peak in the fourth decade and with no sex predilection. Also, limbs were more commonly affected by both benign and malignant tumours.Lipomas topped the benign STT 328 (42.7%) followed by vascular tumours 178 (23.2%). Regarding sarcomas, 29 (24.5%) remained unclassifiable and were typed as Sarcoma Not Otherwise Specified (NOS). For the specifically diagnosed malignancies, leiomyosarcoma 24 (20.3%) topped the list, followed by rhabdomyosarcoma and Ewing’s/Primitive Neuroectodermal Tumour (PNET) 12 (10.1%) each, Dermatofibrosarcoma Protuberans (DFSP) and liposarcoma 11 (9.4%) each and synovial sarcoma 6 (5.1%). Conclusion: Benign STT were more common than sarcomas. Diagnosis and classification of STT should be based on acumen histologic grounds which is sufficient for most benign tumours and to some extent for sarcomas. Undifferentiated sarcomas cannot be categorised without immunohistochemistry. However, loss of some differentiation antigens in undifferentiated cancers often necessitate the use of panels of antibodies, and considerable cases even need further evaluation, like molecular studies.

Revisiting the WHO classification system of soft tissue tumours: emphasis on advanced magnetic resonance imaging sequences. Part 1.

The World Health Organisation (WHO) classification categorises musculoskeletal soft tissue tumours (STT) based on their similarity to normal adult tissue. The most recent WHO classification provides an updated scheme that integrates biological behaviour as a distinguishing feature in each subcategory; STTs are further subdivided as benign, intermediate (locally aggressive or rarely metastasising), and malignant. Although malignant STTs are infrequent in routine orthopaedic radiology practice, musculoskeletal radiologists must be familiar with the imaging appearance of malignant STTs and distinguish them from their benign counterparts for appropriate management. Magnetic resonance imaging (MRI) is the ideal modality for the detection, characterisation, and local staging of STT. This review will discuss the most recent updates to the WHO classification of STT that are relevant to radiologists in a routine clinical practice with MRI correlation. The utility of advanced MRI sequences such as diffusion weighted imaging, dynamic contrast enhanced sequences, and magnetic resonance spectroscopy to provide insight into the biological behaviour of various STTs is highlighted.

Spindle Cell Tumors With RET Gene Fusions Exhibit a Morphologic Spectrum Akin to Tumors With NTRK Gene Fusions

A major breakthrough in the classification of soft tissue tumors has been the recent identification of NTRK-fusion related neoplasms which are amenable to highly effective targeted therapies. Despite these therapeutic opportunities, diagnostic challenges have emerged in recognizing tumors characterized by protein kinase fusions, as they are associated with a wide morphologic spectrum, variable risk of malignancy and a rather nonspecific immunoprofile. As such, NTRK-related fusions may occur in infantile fibrosarcoma, lipofibromatosis-like neural tumors (LPF-NTs), tumors resembling malignant peripheral nerve sheath tumors, etc. Triggered by an index case resembling LPF-NT but harboring RET gene rearrangement, we investigated our files for cases showing RET gene abnormalities to establish their clinicopathologic features. Tumors were tested with a combination of targeted RNA sequencing and fluorescence in situ hybridization methods. Six cases with RET gene rearrangements were identified, all except 1 occurred in children, including 4 infants. Their morphologic spectrum was quite diverse, but closely reproduced the phenotype of NTRK-fusion-positive tumors, including LPF-NTs (n=3), infantile fibrosarcoma-like tumor (n=2) and malignant peripheral nerve sheath tumor-like (n=1). Three cases showed coexpression of S100 and CD34, whereas the remaining 3 had a nonspecific immunoprofile. The tumors ranged morphologically and clinically from benign to highly malignant. None of the LPF-NT cases recurred, whereas 2 patients with malignant histology had a highly aggressive course with distant metastases to lung and other viscera. By targeted RNA sequencing these tumors harbored RET fusions with an identical break in exon 12, which retains the tyrosine kinase domain in the fusion oncoprotein and involving various gene partners (CLIP2, CCDC6, SPECC1L, MYH10, and NCOA4). Our results suggest that RET fusion-positive neoplasms share a similar phenotypic spectrum with the NTRK-positive tumors, displaying either fibroblastic or neural-like differentiation, and spanning a wide spectrum of clinical behavior. These findings open new avenues for targeted therapy with RET inhibitors currently available in clinical trials.

The pathology of soft tissue sarcomas.

Soft tissue sarcomas represent a heterogeneous group of rare malignancies exhibiting mesenchymal differentiation with an overall incidence of around 5/100,000/year. Rarity and morphologic heterogeneity significantly affect diagnostic accuracy; therefore, expertise can be achieved only through access to large number of cases. Soft tissue sarcomas are currently classified on the basis of the 2013 WHO classification of soft tissue tumors that integrate conventional morphology with immunohistochemistry and molecular genetics. The morphologic diagnosis of sarcoma relies on the evaluation as well as the integration of four main features: the shape of the neoplastic cells; the pattern of growth; the quality of the background; the architecture of the vascular network. Immunohistochemical characterization plays a key role in the diagnostic workup of soft tissue sarcomas. The majority of classic differentiation markers tend to show good sensitivity, however, associated with rather limited specificity, making interpretation in context with morphology mandatory. Molecular genetics is increasingly used for diagnostic purposes to distinguish specific subtypes of sarcomas, to support diagnosis in non-canonical clinical presentations and also to distinguish true sarcomas from benign mimickers. With many exceptions, histologic typing does not provide sufficient information for predicting the clinical course of the disease and, therefore, grading systems based on histological parameters were introduced to provide a more accurate estimation of the degree of malignancy of tumors. The three-tiered system devised by the French Federation of Cancer Centers Sarcoma Group (FNCLCC) systems is widely adopted; however, several limitations exist that have led to the development of prognostic nomograms that incorporate the specific histotype as one of the relevant parameters.

Soft tissue tumors : Epidemiology, classification and staging

Benign, intermediate and malignant soft tissue tumors can be differentiated histologically. Furthermore, the tumors can be subdivided according to their linear differentiation. In the new World Health Organization (WHO) classification of soft tissue tumors from 2013 changes have been made relating to the allocation of known entities, e. g. undifferentiated sarcomas have been formed into anew subgroup and are no longer assigned to the fibrohistiocytic tumors. The term malignant fibrous histiocytoma has been replaced by the undifferentiated sarcoma. Furthermore, two new subgroups were incorporated, the nerve sheath tumors and gastrointestinal stromal tumors. These were previously included in the tumor classification of other organ systems. These changes in the new classification are related to the rapid increase in knowledge of the genetics and the cell biology of soft tissue tumors. Malignant soft tissue tumors only represent 1% of all malignant tumors in adults. The largest subgroup of soft tissue tumors in adults is the adipocytic tumors. The liposarcoma, which belongs to this subgroup is one of the most common malignant soft tissue tumors in adults. In childhood malignant soft tissue tumors represent 15% of malignant tumors and rhabdomyosarcoma is the most common malignant soft tissue tumor.

Soft-Tissue Sarcomas of the Abdomen and Pelvis: Radiologic-Pathologic Features, Part 2-Uncommon Sarcomas.

Soft-tissue sarcomas occurring in the abdomen and pelvis are an uncommon but important group of malignancies. Recent changes to the World Health Organization classification of soft-tissue tumors include the movement of gastrointestinal stromal tumors (GISTs) into the soft-tissue tumor classification. GIST is the most common intraperitoneal sarcoma. Liposarcoma is the most common retroperitoneal sarcoma, and leiomyosarcoma is the second most common. GIST, liposarcoma, and leiomyosarcoma account for the majority of sarcomas encountered in the abdomen and pelvis and are discussed in part 1 of this article. Undifferentiated pleomorphic sarcoma (previously called malignant fibrous histiocytoma), dermatofibrosarcoma protuberans, solitary fibrous tumor, malignant peripheral nerve sheath tumor, rhabdomyosarcoma, extraskeletal chondro-osseous sarcomas, vascular sarcomas, and sarcomas of uncertain differentiation uncommonly arise in the abdomen and pelvis and the abdominal wall. Although these lesions are rare sarcomas and their imaging features overlap, familiarity with the locations where they occur and their imaging features is important so they can be diagnosed accurately. The anatomic location and clinical history are important factors in the differential diagnosis of these lesions because metastasis, more-common sarcomas, borderline fibroblastic proliferations (such as desmoid tumors), and endometriosis have imaging findings that overlap with those of these uncommon sarcomas. In this article, the clinical, pathologic, and imaging findings of uncommon soft-tissue sarcomas of the abdomen and pelvis and the abdominal wall are reviewed, with an emphasis on their differential diagnosis.

Current Concepts in Non-Gastrointestinal Stromal Tumor Soft Tissue Sarcomas: A Primer for Radiologists.

Non-gastrointestinal stromal tumor (GIST) soft tissue sarcomas (STSs) are a heterogeneous group of neoplasms whose classification and management continues to evolve with better understanding of their biologic behavior. The 2013 World Health Organization (WHO) has revised their classification based on new immunohistochemical and cytogenetic data. In this article, we will provide a brief overview of the revised WHO classification of soft tissue tumors, discuss in detail the radiology and management of the two most common adult non-GIST STS, namely liposarcoma and leiomyosarcoma, and review some of the emerging histology-driven targeted therapies in non-GIST STS, focusing on the role of the radiologist.

Clinical Retrospective Analysis of 42 Patients with Primary Bone Lymphoma Treated at Maisonneuve-Rosemont Hospital

IntroductionPrimary bone lymphoma (PBL) is an uncommon form of lymphoma. Diffuse large B-cell lymphoma (DLBCL) represents the main histology associated with PBL. Clinicopathological understanding and management of PBL rely only on retrospective series.MethodsCases of DLBCL diagnosed by bone biopsy treated in one referring center between 1993 and 2014 were retrospectively reviewed (Montreal, Canada). Bone biopsies done as part of the bone marrow analysis were excluded. Patients files were analyzed to determine if patient had primary bone lymphoma or systemic lymphoma with bony involvement. We excluded patient with distant lymph node or other extranodal involvement. Data on clinical presentation, staging procedures and treatment management including use of radiotherapy was collected. Staging was performed according to WHO classification of soft tissue tumors (2002). Survival time and time to recurrence were calculated from the date of the first documented treatment until recurrence or death with the Kaplan-Meier method. Prognostic factors of recurrence or death were explored with log-rank tests and Cox proportional hazards models. Competing risks analysis was attempted to isolate deaths from lymphoma and death from other causes. Our study was approved by local research and ethic committees.ResultsWe retrieved 42 cases of PBL with a median age of 63 years (23-83) treated between October 1995 and April 2014. We identified 3/14 (21%) GCB and 11/14 (79%) non-GCB subtypes based on the modified Hans algorithm (Meyer et al., JCO 2011). The most common presenting symptom was pain (88%). 12/42 (33%) patients had an IPI score ≥ 3. We identified 18 (43%) stage I, 11 (26%) stage II and 13 (31%) stage IV. 20/42 (48%) had bulky disease (≥ 10cm). Among the 37 patients treated with curative intent, 36 (97%) received CHOP-based regimen and 23 (62%) received rituximab. 30 of these 37 (81%) patients received additional radiotherapy of which 67% received a dose of radiotherapy between 36-50 Gy. Overall response rate for patients treated with curative intent was 86%. With a median follow up of 64.8 months for the whole cohort, the 5- and 10-year overall survival was 73% and 54%, respectively. The 5- and 10-year progression-free survival was 70% and 49% respectively. Age, LDH, stage (I-II vs IV), ECOG (0-1 vs 2-4), IPI (0-2 vs 3-5), use of radiotherapy or addition of rituximab were associated with differences in survival and progression rates that did not reach statistical significance given the limited number of patients in our cohort and the fact that half of the deaths were attributed to other causes. A larger cohort would be required to demonstrate a benefit with rituximab. Response was based on positron emission tomography-computed tomography (TEP-CT) imaging in 12 patients. There was an insufficient number of patients to evaluate the role of adding radiotherapy in patient complete remission defined by PET-CT.ConclusionOur survival rates reproduce published data from series of PBL (Ramadan et al., Ann Oncol 2007; Bruno Ventre et al., Oncologist 2014), although the benefit of adding rituximab did not reach statistical significance in our cohort. The role of radiotherapy in the era of response defined by PET-CT remains to be defined. DisclosuresFleury:Gilead: Consultancy, Speakers Bureau; Amgen: Consultancy, Speakers Bureau; Roche: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; Lundbeck: Consultancy, Speakers Bureau; Seattle Genetics: Consultancy, Speakers Bureau.

A clinicopathologic study of head and neck rhabdomyosarcomas showing FOXO1 fusion-positive alveolar and MYOD1-mutant sclerosing are associated with unfavorable outcome

BackgroundBased on their distinctive histologic and genetic features, the latest WHO classification of soft tissue tumors includes four pathologic variants of rhabdomyosarcoma (RMS): embryonal (ERMS), alveolar (ARMS), spindle cell-sclerosing (SRMS-ScRMS) and pleomorphic RMS. The aim of this study focused on a detailed clinicopathologic and survival analysis of head and neck RMS (HNRMS) using the latest pathologic and molecular criteria reflecting this new subclassification in a large cohort. Patients and methodsPatients managed for HNRMS in our institution (1996–2015) were analyzed. The presence of a FOXO1 fusion was required for the classification of ARMS. MYOD1 mutations in SRMS-ScRMS were tested when material available. Univariate and multivariate analyses were performed to evaluate variables related to overall survival (OS). ResultsNinety-nine HNRMS patients (52 males and 47 females, mean of 16years) were included in the study after pathologic re-review. The most common location was parameningeal (PM) (n=64), followed by non-orbital/non-PM (n=25) and orbital (n=10). There were 53 ERMS, 33 fusion-positive ARMS and 13 SRMS-ScRMS [SRMS (8); ScRMS (5)]. The 5-year OS rate for ERMS patients was significantly higher (82%) compared to ARMS (53%) and SRMS-ScRMS (50%) [SRMS (75%); ScRMS (30%)]. Univariate analysis showed that survival was dependent on histology (P=0.012), tumor size >5cm (P<0.001), regional lymph node involvement (P=0.002), metastasis at initial presentation (P<0.001), stage (P<0.001), and recurrence (P=0.002). Multivariate analysis confirmed histologic subtype to be significant (P=0.043). ConclusionOur findings reinforce that HNRMS is a heterogenous disease with ARMS and SRMS-ScRMS having an equally unfavorable outcome.

Lipoma of the Middle Finger Hampering its Movements

Dear sir, Lipomas are common soft tissue neoplasms and can be found anywhere in the body, especially in the head and neck region, as well as in the shoulder and back [1]. They are uncommon in the hand and are rarely found in the fingers with reported incidence of 1% [2]. According to WHO committee for the Classification of Soft Tissue Tumors, they are categorized into 9 entities, including lipoma, lipomatosis, lipomatosis of nerve, lipoblastoma, angiolipoma, myolipoma of soft tissue, chondroid lipoma, spindle cell/pleomorphic lipoma and hibernoma. Benign lipomatous lesions may also affect joints and tendon sheaths, either focally or diffusely [3]. Lipomas are often not considered in the initial differential diagnosis of digital swellings. We present a case with right middle finger lipoma involving the proximal interphalangeal joint. A 48-year-old male presented with swelling on the dorsomedial aspect of the proximal interphalangeal joint of the right middle finger, causing difficulty in finger movements (Fig. 1). The lesion had started one and a half year back and gradually increased in size thus causing discomfort in finger movements since last two months. Physical examination showed a 1.5 × 1.5 cm, nontender, subcutaneous swelling on the dorsomedial aspect of the proximal interphalangeal joint associated with some limitation of finger movements. Plain anteroposterior radiograph of the digit showed no invasion of the bone, thus excluding parosteal lipoma from the differential diagnosis. The patient was subjected to exploration of the finger under local anaesthesia using a longitudinal skin incision (Fig. 2). There was no difficulty in excising the swelling as its margins were free. It was excised completely and subjected to histopathology examination. After surgery, patient fully recovered the movements of the involved finger. Grossly, the swelling was 1.5 × 1.0 cm in size and was composed of fatty tissue. Histological results showed the swelling to be a lipoma. There was no evidence of recurrence or any restriction in finger movements during the two years of postoperative follow-up. Fig. 1 Lipoma of right middle finger Fig. 2 Lipoma protruding through incision Lipomas account for approximately 16% of soft tissue mesenchymal tumors. They are rarely encountered in the hand and are extremely rare in the digits. Neoplastic lesions (liposarcoma, lipoblastoma, Giant cell tumour, spindle cell lipoma, angiolipoma, and neural fibrolipoma) and non neoplastic lesions (implantation cyst, pyogenic granuloma, and nodular fasciitis) with clinical characteristics similar to those of a lipoma of the finger should be considered in the differential diagnoses of a mass in the finger. Careful dissection is necessary during the surgical procedure in order to avoid recurrence. Ultrasonography, computerized tomography, or magnetic resonance imaging are useful for more detailed investigations and differential diagnosis [4]. Although a lipoma in the finger is relatively rare, it should be included in the initial differential diagnoses of finger tumours. Although being rare entity, its awareness is imperative since the differential diagnosis from other soft tissue tumors is quite extensive so it should be included in the initial differential diagnoses of finger tumours.

Tumor híbrido de la vaina del nervio periférico de localización digital con componente neurofibroma-perineuroma. Descripción de un caso y revisión de la literatura

Hybrid peripheral nerve sheath tumour is a rare mesenchymal benign neoplasm recently included in the WHO classification of soft tissue tumours. It has a wide distribution but predominantly affects limbs and trunk. Histological findings reveal the presence of 2 or more cellular components originating in the peripheral nerve sheath with variable proportions of neurofibroma, schwannoma and perineurioma. We report a case of a 65-year-old male with a painless nodule in the 5th finger of his left hand which showed microscopic features of neurofibroma and perineurioma. We review the histological and immunohistochemical findings of this unusual, and often over-looked, tumour in the recent literature.

Clinical Characteristics and Outcomes for Solitary Fibrous Tumor (SFT): A Single Center Experience.

Solitary fibrous tumor (SFT) is a mesenchymal neoplasm of fibrous origin. The 2013 WHO classification of soft tissue tumors defines malignant forms as hypercellular, mitotically active (>4 mitosis/10 high-power fields), with cytological atypia, tumor necrosis, and/or infiltrative margins. With an IRB-approved protocol, we investigated patient records and clinicopathologic data from our Sarcoma Database to describe the clinical characteristics of both benign and malignant SFT. All pathology specimens were reviewed by two pathologists. Descriptive statistics and univariate/multivariate survival analysis were performed. Patient records and Social Security Death Index were used to evaluate vital status. Of 82 patients, 47 (57%) were women and 73 (89%) were Caucasian. Median age was 62 years (range, 20 to 89). Thirty-two (39%) patients succumbed to the disease. Primary tumor site was lung/pleura in 28 (34%), abdomen/pelvis in 23 (28%), extremity in 13 (16%), and head/neck in 9 (11%) patients. Pathology was described as benign in 42 (51%) and malignant in 40 (49%) patients. Compared to benign SFT, malignant histology is associated with larger tumor size, higher mitotic counts, metastatic disease at diagnosis, and greater use of chemotherapy and radiation therapy. Gender, age, and tumor site were not significantly different between benign and malignant subtypes. By univariate analysis, only benign vs. malignant variant and complete resection positively impacted overall survival (P = 0.02 and P<0.0001, respectively). In the multivariable analysis of overall survival, receiving chemotherapy or not receiving surgery were two variables significantly associated with higher failure rate in overall survival: patients with chemotherapy vs. no chemotherapy (P = 0.003, HR = 4.55, with 95% CI: 1.68–12.34) and patients without surgery vs. with surgery (P = 0.005, HR = 25.49, with 95% CI: 2.62–247.57). Clear survival differences exist between benign and malignant SFT. While surgery appears to be the best treatment option for benign and malignant SFT, better systemic therapies are needed to improve outcomes of patients with metastatic, malignant SFT.

Omental mesenteric myxoid hamartoma, a subtype of inflammatory myofibroblastic tumor? Considerations based on the histopathological evaluation of four cases.

Omental mesenteric myxoid hamartoma (OMH) is a distinctive myxoid lesion of infancy, characterized by a benign clinical behavior. In the current World Health Organization (WHO) classification of soft tissue tumors, it is considered as part of the morphologic spectrum of inflammatory myofibroblastic tumors (IMT), but this relationship with IMT is still subject to debate. Four lesions with histologic features of OMH occurring in newborns and toddlers are described and compared with classic, ALK-positive IMT. All OMH showed a peculiar dot-like immunostaining for ALK, which, in one of the cases, was cytogenetically found to be associated with an inversion of the ALK gene. While OMHs were positive for smooth muscle actin (SMA), desmin, WT1, podoplanin, and cytokeratins (CAM5.2 and AE1-3), IMT were consistently positive only for SMA (10 cases). ALK-1 displayed cytoplasmic staining in IMT and characteristic paranuclear dot-like staining in OMH.

Mesenchymal tumours of the mediastinum--part I.

The mediastinum is an anatomically defined space in which organs and major blood vessels reside with surrounding soft tissue elements. The thymus is an important organ in the mediastinum, and many of the masses encountered in the mediastinum are related to this organ. Most neoplasms diagnosed in the mediastinum are epithelial tumours (thymomas and thymic carcinomas), lymphomas or germ cell tumours. In contrast, soft tissue tumours of the mediastinum are rare. In 1963, Pachter and Lattes systematically reviewed soft tissue pathology of the mediastinum, covering the hitherto described [2, 226, 227] In this review, based on the 2013 WHO classification of soft tissue tumours and the 2015 WHO classification of tumours of the lung, pleura, thymus and heart, we provide an updated overview of mesenchymal tumours that may be encountered in the mediastinum.

Mesenchymal tumours of the mediastinum--part II.

This is the second part of a two-part review on soft tissue tumours which may be encountered in the mediastinum. This review is based on the 2013 WHO classification of soft tissue tumours and the 2015 WHO classification of tumours of the lung, pleura, thymus and heart and provides an updated overview of mesenchymal tumours that have been reported in the mediastinum.

Changes in the WHO classification of soft tissue tumors

This article reviews key changes in the current 2013 World Health Organization Classification of soft tissue tumors.

The evolving classification of soft tissue tumours – what’s next?

With the advent of the new format for WHO tumor classifications, there have been major changes in each of the most recent volumes (2002 and 2013) concerning soft tissue neoplasms. Perhaps foremost has been the disappearance of ‘malignant fibrous histiocytoma’ and ‘hemangiopericytoma’. In 2013 the category of undifferentiated sarcomas was introduced and a very large amount of new genetic data across many tumor types was incorporated. Even since the completion of the latest volume (which was published almost a year after the consensus meeting at which the content was finalised), there have been important new findings in solitary fibrous tumour, a subset of rhabdomyosarcomas and among round cell sarcomas. Increasing genetic overlap among seemingly distinct tumour types is emerging and, in the future, the relative importance of phenotype versus genotype will need to be determined. There also remain opportunities to address significant nomenclatural problems.

Quatrième édition de la classification OMS des tumeurs des tissus mous

The new World Health Organization (WHO) classification of soft tissue tumours was published in 2013, 11years after the previous edition. This new classification includes several changes: newly included sections (gastrointestinal stromal tumors…), newly recognized entities (pseudomiogenic haemangioendothelioma, haemosiderotic fibrolipomatous tumour…), and new genetic and molecular data leading to better understanding and definition of tumours, and are useful as diagnostic tools. This brief review summarizes changes in this new edition of the WHO classification of tumours of soft tissue.