Histological diagnostic discrepancy and its clinical impact in bone and soft tissue tumors referred to a sarcoma center.

Histological diagnosis of sarcomas (malignant bone and soft tissue tumors) is challenging due to their rarity, morphological diversity, and constantly evolving diagnostic criteria. In this study, we aimed to assess the concordance in histological diagnosis of bone and soft tissue tumors between referring hospitals and a tertiary sarcoma center and analyzed the clinical impact of the diagnostic alteration. We analyzed 628 consecutively accessioned specimens from 624 patients who visited a specialized sarcoma center for treatment. The diagnoses at referring hospitals and those at the sarcoma center were compared and classified into four categories: agreed, disagreed, specified, and de-specified. Of the 628 specimens, the diagnoses agreed in 403 (64.2%) specimens, whereas some changes were made in 225 (35.8%) specimens: disagreed in 153 (24.3%), specified in 52 (8.3%), and de-specified in 20 (3.2%) cases. The benign/intermediate/malignant judgment changed for 92 cases (14.6%). The diagnostic change resulted in patient management modification in 91 cases (14.5%), including surgical and medical treatment changes. The main inferred reason for the diagnostic discrepancies was a different interpretation of morphological findings of the tumor, which accounted for 48.9% of the cases. This was followed by the unavailability of specialized immunohistochemical antibodies and the unavailability of genetic analysis. In summary, our study clarified the actual clinical impact of diagnostic discrepancy in bone and soft tissue tumors. This may underscore the value of pathology consultation, facilitating access to specialized diagnostic tools, and continued education. These measures are expected to improve diagnostic precision and ultimately benefit patients.

The Incidence of Multiple Fusions in a Series of Pediatric Soft Tissue and Bone Tumors.

BACKGROUND: Next generation sequencing (NGS) has increased the detection of fusion genes in cancer. NGS has found multiple fusions in single tumor samples; however, the incidence of this in pediatric soft tissue and bone tumors (PSTBTs) is not well documented. The aim of this study is to catalogue the incidence of multiple fusions in a series of PSTBTs, and apply a modified gene fusion classification system to determine clinical relevance. METHODOLOGY: RNA from 78 bone and soft tissue tumors and 7 external quality assessment samples were sequenced and analyzed using recently-described Metafusion (MF) software and classified using a modification of previously-published schema for fusion classification into 3 tiers: 1, strong clinical significance; 2, potential clinical significance; and 3, unknown clinical significance. RESULTS: One-hundred forty-five fusions were detected in 85 samples. Fifty-five samples (65%) had a single fusion and 30 (35%) had more than 1 fusion. No samples contained more than 1 tier 1 fusion. There were 40 tier 1 (28%), 36 tier 2 (24%), and 69 (48%) tier 3 fusions. CONCLUSIONS: A significant percentage of PSTBTs harbor more than 1 fusion, and by applying a modified fusion classification scheme, the potential clinical relevance of such fusions can be determined.

Recent advances in molecular profiling of bone and soft tissue tumors.

The molecular characterization of soft tissue and bone tumors is a rapidly evolving field that has changed the perspective of how these tumors are diagnosed today. Morphology and clinico-radiological context still represent the cornerstone of diagnostic considerations but are increasingly complemented by molecular data that aid in objectifying and confirming the classification. The spectrum of analyses comprises mutation or gene fusion specific immunohistochemical antibodies, fluorescence in situ hybridization, DNA and RNA sequencing as well as CpG methylation profiling. This article provides an overview of which tools are presently available to characterize bone and soft tissue neoplasms molecularly, what limitations should be considered, and what conclusions can be drawn from the individual findings.

Fusion-driven Spindle Cell Rhabdomyosarcomas of Bone and Soft Tissue: A Clinicopathologic and Molecular Genetic Study of 25 Cases.

The evolving classification of rhabdomyosarcoma (RMS) now includes spindle cell RMS (SRMS). Bone/soft tissue SRMS often harbor TFCP2, or less often MEIS1 rearrangements. We studied 25 fusion-driven SRMS involving bone (n = 19) and soft tissue (n = 6). Osseous SRMS occurred in 13 women and 6 men (median age: 41 years) and involved the pelvis (5), sacrum (2), spine (4), maxilla (4), mandible (1), skull (1), and femur (2). Follow-up (median: 5 months) demonstrated local recurrence in 2/16 and distant metastases in 8/17 patients (median time to metastasis: 1 month). Eight patients died of disease; 9 were alive with disease. Soft tissue SRMS occurred in 4 men and 2 women (median: 50 years). Follow-up (median: 10 months) revealed distant metastasis at diagnosis (1), alive with unresected tumor (1), and no evidence of disease (4). Next-generation sequencing demonstrated FUS::TFCP2 (12), EWSR1::TFCP2 (3) and MEIS1::NCOA2 (2); FISH identified EWSR1 (2) rearrangements. Most TFCP2-rearranged SRMS (13/17) showed spindled/epithelioid morphology, rarely with rhabdomyoblasts. The bone tumors were diffusely desmin and MyoD1 positive with limited myogenin; 10/13 were ALK -positive and 6/15 were keratin positive. Soft tissue SRMS harbored EWSR1::TFCP2, MEIS1::NCOA2, ZFP64::NCOA2, MEIS1::FOXO1, TCF12::VGLL3 and DCTN1::ALK, and displayed spindled/epithelioid, leiomyomatous, and myxofibrosarcoma-like morphologies. Immunohistochemistry (IHC) was positive for MyoD1 (6/6), focal desmin (5/6), myogenin (3/6), and keratin (1/6). We conclude that TFCP2-rearranged SRMS of bone and soft tissue show consistent morphologic and IHC features, likely representing a distinct subset of RMS. Non-TFCP2 fusion-positive SRMS could represent a single RMS subset, multiple subtypes of RMS, or "fusion-defined" sarcomas with rhabdomyoblastic differentiation.

EWSR1::NR4A3 gene fusion in a cutaneous atypical myoepithelial neoplasm.

Myoepithelial neoplasms of the skin and soft tissue are rare and share histopathologic features with their salivary gland counterpart. We present a case of an atypical myoepithelial neoplasm from the back of a 72-year-old female. This lesion harbored an EWSR1::NR4A3 gene fusion, a genetic signature characteristically seen in extraskeletal myxoid chondrosarcoma. To our knowledge, this is a unique case of an atypical cutaneous myoepithelial neoplasm harboring EWSR1::NR4A3 fusion.

Expanding the Spectrum of Perioral Myogenic Tumors in Pediatric Patients: An SRF::NCOA2 Fused Perivascular Tumor of the Philtrum.

BACKGROUND: Perivascular tumors, which include myopericytoma and myofibroma, are rare benign soft tissue neoplasms composed of perivascular smooth muscle cells. Most demonstrate characteristic morphology and are readily diagnosed. However, a recently identified hypercellular subset shows atypical histologic features and harbor unique SRF gene fusions. These cellular perivascular tumors can mimic other more common sarcomas with myogenic differentiation. METHODS: Clinical, radiological, morphological, immunohistochemical, and molecular findings were reviewed. RESULTS: A slow-growing, fluctuant mass was noted within the philtrum at 16 months. Ultrasonography revealed a well-circumscribed cystic hypoechoic lesion. A small (1.0 cm), tan, well-circumscribed soft-tissue mass was excised after continued growth. Histologically, the encapsulated tumor was hypercellular and composed of spindle cells with predominantly-storiform architecture, focal perivascular condensation, dilated branching thin-walled vessels, increased mitoses, and a smooth muscle immunophenotype. An SRF::NCOA2 fusion was identified. CONCLUSION: We report the first case of an SRF-rearranged cellular myopericytoma in the perioral region in a young child. This case expands the differential diagnosis of perioral soft tissue tumors with myogenic differentiation. We highlight key clinical, pathological, and molecular features. As we illustrate, these rare tumors pose a considerable diagnostic challenge, and risk misdiagnosis as sarcoma, most notably spindle cell rhabdomyosarcoma.

Mucosal Soft Tissue Lesions.

Mucosal soft tissue lesions are fairly common in the pediatric population. However, the precise prevalence is unknown. This is the result of the limited number of studies, the use of various diagnostic criteria in those studies, and the transient nature of commonly encountered lesions in this population. In this section, we seek to familiarize the pediatric pathologist with a sampling of mucosal soft tissue lesions encountered in pediatric patients, highlight key diagnostic features and correlations with systemic diseases should they exist.

Postoperative drainage management and wound complications following resection of lower limb soft tissue tumors: a retrospective cohort study.

PURPOSE: Postoperative wound complications are common in patients undergoing resection of lower extremity soft tissue tumors. Postoperative drainage therapy ensures adequate wound healing but may delay or complicate it. The aim of this study is to evaluate the incidence of postoperative wound complications and delayed or prolonged drainage treatment and to propose a standardized definition and severity grading of complex postoperative courses. METHODS: A monocentric retrospective analysis of 80 patients who had undergone primary resection of lower extremity soft tissue tumors was performed. A new classification was developed, which takes into account postoperative drainage characteristics and wound complications. Based on this classification, risk factors and the prognostic value of daily drainage volumes were evaluated. RESULTS: According to this new definition, regular postoperative course grade 0 (no wound complication and timely drainage removal) occurred in 26 patients (32.5%), grade A (minor wound complications or delayed drainage removal) in 12 (15.0%), grade B (major wound complication or prolonged drainage therapy) in 31 (38.8%), and grade C (reoperation) in 11 (13.7%) patients. Tumor-specific characteristics, such as tumor size (p = 0.0004), proximal tumor location (p = 0.0484), and tumor depth (p = 0.0138) were identified as risk factors for complex postoperative courses (grades B and C). Drainage volume on postoperative day 4 was a suitable predictor for complex courses (cutoff of 70 ml/d). CONCLUSION: The proposed definition incorporates wound complications and drainage management while also being clinically relevant and easy to apply. It may serve as a standardized endpoint for assessing the postoperative course after resection of lower extremity soft tissue tumors.

Small (≤5 cm) soft tissue tumors of the extremity and superficial trunk: MRI features and demographic characteristics associated with malignancy.

BACKGROUND: Although a substantial proportion of small soft tissue tumors are malignant, magnetic resonance imaging (MRI) features and demographic characteristics associated with these tumors have not been well described. PURPOSE: To investigate the MRI features and demographic characteristics associated with small (≤5 cm) malignant soft tissue tumors, and to identify independent predictors that allow differentiation of small benign and malignant soft tissue tumors. MATERIAL AND METHODS: This retrospective study evaluated patients who underwent surgical excision of small soft tissue tumors of the extremities and superficial trunk, and preoperative contrast-enhanced MRI. Seven MRI findings (tumor depth, tumor-fascia relationship, heterogeneity of signal intensity, necrosis, peritumoral edema, peritumoral enhancement, and margin) and two demographic parameters (age and sex) were included in univariate and multivariate logistic regression analyses to identify independent predictors of small malignant soft tissue tumors. RESULTS: A total of 221 patients (102 men; mean age=45.6 ± 17.6 years) with 72 malignant and 149 benign tumors were included. In the univariate analysis, peritumoral edema (odds ratio [OR] = 3.854; P < 0.001) and peritumoral enhancement (OR = 3.966; P < 0.001) and patient age (≥46 years) (OR = 2.154; P = 0.009) were significantly associated with malignancy. Multivariate analysis showed that peritumoral enhancement on MRI (OR = 3.728; P < 0.001) and patient age (≥46 years) (OR = 1.907; P = 0.036) were independent predictors of malignancy. The combination of these two parameters showed accuracy of 75.1%, sensitivity of 55.6%, and specificity of 84.6% to predict malignancy. CONCLUSION: Among several MRI and demographic features, the presence of peritumoral enhancement on MRI and patient age (≥46 years) were independent predictors of malignancy in small soft tissue tumors.

Percutaneous biopsy of musculoskeletal tumors and the potential for needle tract seeding: technical considerations, current controversies, and outcomes.

Multidisciplinary communication and planning between the musculoskeletal radiologist and orthopedic oncologist are essential for proper biopsy planning when a primary musculoskeletal malignancy is suspected. Image-guided percutaneous biopsy allows for real-time visualization of the biopsy needle and surrounding structures, combining high diagnostic accuracy with safety and cost-effectiveness. However, determining a surgically optimal biopsy trajectory for a mass can be technically challenging due to critical surrounding anatomy or challenging needle approach angles. Inappropriately placed biopsies can have serious repercussions on patient function and oncological survival. The potential for needle tract seeding and local recurrence after biopsy of sarcoma has been central to the debate regarding the need for excision of the biopsy tract. This multidisciplinary review highlights current controversies in the field, including the issue of core needle biopsy tracts and their excision, technical considerations and advances in image-guidance in the setting of challenging biopsies, advances in histopathological diagnostics with implications for targeted therapy in sarcoma, as well as surgical and oncological outcomes after needle tract biopsy.

Fibrous hamartoma of infancy. Radiologic-pathologic study of 21 cases: 8 with predominant pseudoangiomatous pattern.

Fibrous hamartoma of infancy (FHI) is a very rare benign soft tissue lesion that principally affects the axilla, trunk, and upper extremities of children younger than 2 years. It is usually cured by local excision. Histologically, these lesions have a triphasic morphology in an organoid pattern: mature adipose tissue, fibroblastic/myofibroblastic trabeculae, and small round cell nests in a myxoid matrix. However, morphologic variants have recently been described. Focal areas with a pseudoangiomatous pattern have been found in some FHI, but few cases with predominant pseudoangiomatous areas have been previously described in the medical literature. We report 21 new cases of FHI, 8 of them with a predominant pseudoangiomatous pattern. Our cases with a predominant pseudoangiomatous pattern did not present specific radiological findings.

[Changes in the WHO classification (2020) of soft tissue tumors]. / Izmeneniya v klassifikatsii VOZ (2020 g.) opukholei myagkikh tkanei.

The article provides an overview of the main changes in the current (2020) WHO classification of soft tissue tumors, as well as selected updates that have occurred since the release of the classification.

[Surgical treatment of cervical neurovascular bundle tumors]. / Khirurgicheskoe lechenie bol'nykh s opukholyami sosudisto-nervnogo puchka shei.

OBJECTIVE: To determine the main principles of a patient-oriented individual approach to diagnosis and surgical treatment of cervical neurovascular bundle tumors considering the capabilities of neurosurgical hospital. MATERIAL AND METHODS: There were 92 patients with cervical soft tissue tumors affecting neurovascular bundle. Age of patients ranged from 9 to 81 years (mean 47). There were 65.1% women and 34.9% men. We found chemodectoma (47.4%), neurofibroma (15.8%), neurinoma (13.2%), papillary thyroid cancer (5.3%), salivary gland heterotopia (5.3%), salivary gland adenocarcinoma (5.3%), Hodgkin lymphoma (2.6%), hemangioendothelioma (2.6%) and cavernous lymphangioma (2.6%). Diagnostic algorithm included neurological examinations, Doppler ultrasound of supra-aortic arteries, transcranial ultrasound of cerebral vessels, MRI of cervical soft tissues, CT-AG, MR-AG, CT-perfusion, direct selective angiography. RESULTS: A total of 94 surgical interventions were performed. All surgeries were performed using surgical optics and neurophysiological monitoring of cranial nerves IX, X, XII. We chose resection technique depending on localization, histological features and blood supply of tumor. En-bloc resection was performed in 46 cases, removal of fragments - in 23 cases, intracapsular resection of tumor followed by resection of the capsule - in 26 cases. Total and subtotal resection was performed in 68 (72%) and 23 (24%) cases, respectively. Three (4%) patients underwent partial resection of infiltrative tumors for carotid artery decompression and histological analysis. In 76% of cases, baseline symptoms of disease regressed after surgery. Persistent moderate bulbar disorders were observed in 16 patients (17%). Ischemic complications with additional surgical interventions were observed in 2 cases. CONCLUSION: Patients with cervical soft tissue tumors require individual approach regarding choosing the optimal surgical treatment including possible preoperative embolization of tumor, en-bloc or intracapsular resection and carotid artery repair.

Primary Site Identification of Soft-Tissue Mass: Things to Know in MRI Assessment.

The spectrum of soft-tissue mass is varied, including neoplastic and nonneoplastic/inflammatory lesions. However, soft-tissue tumors have similar imaging findings and, therefore, the diagnosis of soft-tissue mass is challenging. Although careful assessment of the internal characteristics on imaging can often narrow the differential diagnoses, the differential diagnosis may be out of the question if identification of the soft-tissue mass origin is missed. The purpose of this article is to review the imaging findings and the essential anatomy to identify the primary site of the soft-tissue mass, and discuss the associated potential pitfalls. In order not to fall into a pitfall, recognition of characteristic imaging findings indicating the origin of the soft-tissue mass and anatomical knowledge of the normal tissue distribution are necessary. LEVEL OF EVIDENCE: 5 TECHNICAL EFFICACY STAGE: 3.

MRI evaluation of soft tissue tumors: comparison of a fast, isotropic, 3D T2-weighted fat-saturated sequence with a conventional 2D T2-weighted fat-saturated sequence for tumor characteristics, resolution, and acquisition time.

OBJECTIVES: To test whether a 4-fold accelerated 3D T2-weighted (T2) CAIPIRINHA SPACE TSE sequence with isotropic voxel size is equivalent to conventional 2DT2 TSE for the evaluation of intrinsic and perilesional soft tissue tumors (STT) characteristics. METHODS: For 108 patients with histologically-proven STTs, MRI, including 3DT2 (CAIPIRINHA SPACE TSE) and 2DT2 (TSE) sequences, was performed. Two radiologists evaluated each sequence for quality (diagnostic, non-diagnostic), tumor characteristics (heterogeneity, signal intensity, margin), and the presence or absence of cortical involvement, marrow edema, and perilesional edema (PLE); tumor size and PLE extent were measured. Signal-to-noise (SNR) and contrast-to-noise (CNR) ratios and acquisition times for 2DT2 in two planes and 3DT2 sequences were reported. Descriptive statistics and inter-method agreement were reported. RESULTS: Image quality was diagnostic for all sequences (100% [108/108]). No difference was observed between 3DT2 and 2DT2 tumor characteristics (p < 0.05). There was no difference in mean tumor size (3DT2: 2.9 ± 2.5 cm, 2DT2: 2.8 ± 2.6 cm, p = 0.4) or PLE extent (3DT2:0.5 ± 1.2 cm, 2DT2:0.5 ± 1.0 cm, p = 0.9) between the sequences. There was no difference in the SNR of tumors, marrow, and fat between the sequences, whereas the SNR of muscle was higher (p < 0.05) on 3DT2 than 2DT2. CNR measures on 3DT2 were similar to 2DT2 (p > 0.1). The average acquisition time was shorter for 3DT2 compared with 2DT2 (343 ± 127 s vs 475 ± 162 s, respectively). CONCLUSION: Isotropic 3DT2 MRI offers higher spatial resolution, faster acquisition times, and equivalent assessments of STT characteristics compared to conventional 2DT2 MRI in two planes. 3DT2 is interchangeable with a 2DT2 sequence in tumor protocols. KEY POINTS: • Isotropic 3DT2 CAIPIRINHA SPACE TSE offers higher spatial resolution than 2DT2 TSE and is equivalent to 2DT2 TSE for assessments of soft tissue tumor intrinsic and perilesional characteristics. • Multiplanar reformats of 3DT2 CAIPIRINHA SPACE TSE can substitute for 2DT2 TSE acquired in multiple planes, thereby reducing the acquisition time of MRI tumor protocols. • 3DT2 CAIPIRINHA SPACE TSE and 2DT2 TSE had similar CNR of tissues.

Diagnostic delay in soft tissue tumors: a single-center study of a university cancer center with a focus on health services research.

BACKGROUND: Lumps and soft tissue tumors (STT) are frequent reasons for consulting a physician. Most STT are benign, and lumps are not always associated with a tumor. MRI is the most advanced imaging modality to assist a provisional diagnosis of STT. Only a small fraction of STT is malignant, these soft tissue sarcomas are known for their aggressive growth. The study aims to analyze the influence of the MRI report on the speed of treatment of patients with suspected STT. METHODS: This was a retrospective, longitudinal, single-center study from 2011-2020. We included adult patients who had biopsies or resections of masses suspicious for STT in MRI exams. MRI reports were classified as benign (I), intermediate/unclear (II), or malignant (III). For these cohorts, time was statistically analyzed from MRI scan to first contact with the University cancer center (UCC) and surgery. Furthermore, distance in kilometers from the patients´ home to the UCC was examined and compared to age and suspected malignancy. RESULTS: Three hundred two patients (♀130; ♂172) were included. Histologic analyses revealed 286 tumors. The average age of the patients was 54.7(SD: 16.2) years. Malignant tumors were more often suspected in older patients (p = 0.0098). Patients with a benign diagnosed tumor in MRI contacted the UCC after an average of 31.3 (SD: 47.8) days. In contrast, patients with suspicion of a malignant tumor contacted the UCC significantly earlier, after 14.1 days (SD: 17.1); p = 0.0098. Likewise, the time between first contact and biopsy/resection was 32.8 days (SD: 35.7) for suspiciously benign tumors, and potentially malignant tumors were treated significantly faster 14.8 (SD: 16.0) days; (p = 0.028). Patients traveled on average 47.5 km (range: 0.5-483) to contact a specialized physician at the UCC. Suspected degree of malignancy or patient´s age had no statistical influence on traveled distance. DISCUSSION: The treatment speed depended to a great extent on the suspected malignancy of the STT in the MRI report. The provisional diagnoses from the radiologist highly influenced the time delay between MRI scan and first contact to the UCC and surgical treatment. No discrimination of age or distance to the UCC was observed in this study.

Can homogeneous, lipomatous tumors be primarily resected without biopsy? A retrospective analysis of 240 tumors.

BACKGROUND: According to guidelines, every soft tissue tumor (STT) larger than 3 cm should be biopsied before definitive resection. Advances in magnetic resonance imaging (MRI) improve the possibility to give a provisional diagnosis of the tumor's entity. Can lipomas and atypical lipomatous tumors (ALTs) of the extremities therefore be primarily marginally resected based on interpretation of MR images without a previous biopsy?. METHODS: In this retrospective, single-center study, 240 patients with the suspicion of a lipomatous tumor in MRI and surgical treatment in our institution between 2011 and 2020 were included. MR imaging was performed before surgery. All resected specimens underwent histopathological analysis. RESULTS: The collective comprised 142 tumors that were suspected as lipoma or ALT by the radiologist and underwent primary marginal resection (PMR). One case had myxoid liposarcoma that was underestimated on MRI and needed radical follow-up resection. One-hundred forty-one patients were cured after PMR. Ninety-eight patients were biopsied initially and in 93 cases resected afterwards according to the necessary oncological margins. CONCLUSION: In our institution, PMR is performed if a lipoma or ALT is suspected on MR imaging. Our treatment method and the diagnostic algorithm are presented. Primary resection spares patients from one surgical procedure, but a slight risk for underestimation of the tumor remains.

Mismatch repair deficiency is rare in bone and soft tissue tumors.

INTRODUCTION: There has been an increased demand for mismatch repair (MMR) status testing in sarcoma patients after the success of immune checkpoint inhibition (ICI) in MMR deficient tumors. However, data on MMR deficiency in bone and soft tissue tumors is sparse, rendering it unclear if routine screening should be applied. Hence, we aimed to study the frequency of MMR deficiency in bone and soft tissue tumors after we were prompted by two (potential) Lynch syndrome patients developing sarcomas. METHODS: Immunohistochemical expression of MLH1, PMS2, MSH2 and MSH6 was assessed on tissue micro arrays (TMAs), and included 353 bone and 539 soft tissue tumors. Molecular data was either retrieved from reports or microsatellite instability (MSI) analysis was performed. In MLH1 negative cases, additional MLH1 promoter hypermethylation analysis followed. Furthermore, a systematic literature review on MMR deficiency in bone and soft tissue tumors was conducted. RESULTS: Eight MMR deficient tumors were identified (1%), which included four leiomyosarcoma, two rhabdomyosarcoma, one malignant peripheral nerve sheath tumor and one radiation-associated sarcoma. Three patients were suspected for Lynch syndrome. Literature review revealed 30 MMR deficient sarcomas, of which 33% were undifferentiated/unclassifiable sarcomas. 57% of the patients were genetically predisposed. CONCLUSION: MMR deficiency is rare in bone and soft tissue tumors. Screening focusing on tumors with myogenic differentiation, undifferentiated/unclassifiable sarcomas and in patients with a genetic predisposition / co-occurrence of other malignancies can be helpful in identifying patients potentially eligible for ICI.

Staging and Classification of Primary Musculoskeletal Bone and Soft-Tissue Tumors According to the 2020 WHO Update, From the AJR Special Series on Cancer Staging.

Staging of primary musculoskeletal bone and soft-tissue tumors is most commonly performed using the AJCC and the Enneking or Musculoskeletal Tumor Society (MSTS) staging systems. Radiologic imaging is integral in achieving adequate musculoskeletal neoplastic staging by defining lesion extent and identifying regional lymph node involvement and distant metastatic disease. Additional important features in surgical planning, though not distinct components of the staging systems, include cortical involvement, joint invasion, and neurovascular encasement; these features are optimally evaluated by MRI. In 2020, the WHO updated the classification of primary musculoskeletal tumors of soft tissue and bone. The update reflects the continued explosion in identification of novel gene alterations in many bone and soft-tissue neoplasms. This growth in gene alteration identification has resulted in newly designated lesions, reclassification of lesion categories, and improved specificity of diagnosis. Although radiologists do not need to have a comprehensive knowledge of the pathologic details, a broad working understanding of the most recent update is important to aid accurate and timely diagnosis given that histologic grading is a component of all staging systems. By using a multidisciplinary approach for primary musculoskeletal neoplasms involving colleagues in pathology, orthopedic oncology, radiation oncology, and medical oncology, radiologists may promote improved diagnosis, treatment, and outcomes.

Second Report of PDE10A-BRAF Fusion in Pediatric Spindle Cell Sarcoma With Infantile Fibrosarcoma-Like Morphology Suggesting PDE10A-BRAF Fusion Is a Recurrent Event.

Infantile/congenital fibrosarcoma (IFS) is the most common soft tissue tumor in children less than one year of age. The most common anatomic site of IFS is in the extremities or trunk, and rarely in the abdomen or retroperitoneum. Approximately 70-90% of cases are characterized by a distinct t(12;15)(p13;q25) translocation resulting in an ETV6-NTRK3 gene fusion. As such, TRK inhibitors are considered frontline therapy in TRK-fusion positive IFS. The ETV6-NTRK3 fusion is also detected in congenital mesoblastic nephroma (CMN) and less frequently in myeloid leukemias, secretory breast carcinoma, and mammary-type secretory carcinoma of the skin and salivary glands. Infrequently, cases of tumors with IFS-like morphology without the characteristic ETV6-NTRK3 gene fusion have been identified. Herein, an ETV6-NTRK3 fusion negative spindle cell sarcoma with IFS-like morphology subjected to genomic profiling revealed a PDE10A-BRAF fusion, a fusion event that has been detected previously in an isolated case of undifferentiated infantile sarcoma.