First report of spontaneous hepatic fibrosarcoma in a white-tufted marmoset (Callithrix jacchus) kept in captivity.

Reports of sarcomas in nonhuman primates are scarce and, specifically, primary hepatic sarcomas are rare, as in humans. This is the first report of an aggressive hepatic fibrosarcoma in a young adult Callithrix jacchus. The final postmortem diagnosis was obtained by means of immunohistochemical analysis, which confirmed the tumor histogenesis.

Uterine Sarcoma With EML4::NTRK3 Fusion: A Spectrum of Mesenchymal Neoplasms Harboring Actionable Gene Fusions.

NTRK gene fusions are part of a paradigm shift in oncology, arising as one of the main genomic alterations with actionability in the so-called "agnostic setting." In gynecologic pathology, the recent description of uterine sarcoma resembling fibrosarcoma and with NTRK rearrangements ( NTRK -rearranged uterine sarcoma) highlights the importance of recognizing clinicopathological cues that can lead to genomic profiling. Herein, we report the case of a 43-year-old woman presenting with vaginal bleeding and pelvic mass. Histopathology of the tumor showed moderately atypical spindle cells arranged in long fascicles reminiscent of fibrosarcoma, along with immunohistochemical positivity for S100, CD34, and pan-tropomyosin receptor kinase. This prompted RNA-sequencing and the finding of a rare EML4::NTRK3 fusion. Clinical, histologic, and molecular findings are described, in addition to discussions regarding differential diagnoses and possible implications of the findings in clinical practice.

The Role of Methylation Analysis in Distinguishing Cellular Myxoma from Low-Grade Myxofibrosarcoma.

Cellular myxoma is a benign soft tissue tumor frequently associated with GNAS mutation that may morphologically resemble low-grade myxofibrosarcoma. This study aimed to identify the undescribed methylation profile of cellular myxoma and compare it to myxofibrosarcoma. We performed molecular analysis on twenty cellular myxomas and nine myxofibrosarcomas and analyzed the results using the methylation-based DKFZ sarcoma classifier. A total of 90% of the cellular myxomas had GNAS mutations (four loci had not been previously described). Copy number variations were found in all myxofibrosarcomas but in none of the cellular myxomas. In the classifier, none of the cellular myxomas reached the 0.9 threshold. Unsupervised t-SNE analysis demonstrated that cellular myxomas form their own clusters, distinct from myxofibrosarcomas. Our study shows the diagnostic potential and the limitations of molecular analysis in cases where morphology and immunohistochemistry are not sufficient to distinguish cellular myxoma from myxofibrosarcoma, particularly regarding GNAS wild-type tumors. The DKFZ sarcoma classifier only provided a valid prediction for one myxofibrosarcoma case; this limitation could be improved by training the tool with a more considerable number of cases. Additionally, the classifier should be introduced to a broader spectrum of mesenchymal neoplasms, including benign tumors like cellular myxoma, whose distinct methylation pattern we demonstrated.

COL1A1-PDGFB Fusion Associated Fibrosarcoma of the Uterine Corpus: A Case Report and Literature Review.

Uterine collagen type 1 alpha 1 (COL1A1) and platelet-derived growth factor beta chain (PDGFB) fusion associated fibrosarcoma is a recently described entity characterized by a specific translocation t(17;22) (q22;q13) leading to the formation of COL1A1-PDGFB fusion transcripts that are typically associated with dermatofibrosarcoma protuberans. So far, only 4 cases of COL1A1-PDGFB fusion associated fibrosarcoma involving the female reproductive system have been reported in the literature. All cases showed strong diffuse expression of CD34. COL1A1-PDGFB fusion associated fibrosarcomas are aggressive tumors with a propensity for chemotherapy resistance and a poor prognosis. We are reporting the fifth case of a uterine COL1A1-PDGFB fusion associated fibrosarcoma. A 58-yr-old female presented with a large uterine mass with extension into bilateral pelvic sidewalls, mesentery of rectosigmoid colon and the vagina. A hysterectomy, bilateral salpingo-oophorectomy, and tumor debulking procedure was performed. Microscopic evaluation revealed a mitotically active cellular spindle cell neoplasm with focal osteoclast like giant cells, myxoid changes and necrosis. CD34 was diffusely and strongly positive throughout the tumor. Next-generation sequencing showed presence of the COL1A1-PDGFB fusion. The patient was treated with multiple chemotherapy regimens, however, progressed under therapy with worsening symptoms and development of extensive pelvic disease. She died of disease 13 mo after the initial diagnosis. In summary, uterine COL1A1-PDGFB fusion associated fibrosarcomas are rare tumors with aggressive clinical behavior that need to be considered in the differential diagnosis of CD34-positive uterine spindle cell neoplasms. Novel treatment options may include imatinib, a tyrosine kinase inhibitor used for treatment of advanced and unresectable dermatofibrosarcoma protuberans that was given in 1 uterine sarcoma case and showed promising initial response.

Sclerosing Epithelioid Fibrosarcoma of the Liver in a Pediatric Patient.

Sclerosing epithelioid fibrosarcoma (SEF) is a rare but aggressive sarcoma. We report the first case of hepatic SEF in pediatric patient, which is also the second case in literature. A 17-year-old previously healthy female presented with a liver mass measuring 13.7 cm in greatest dimension and mild elevation of liver enzymes and cancer antigen 19-9. Needle biopsy revealed multiple cores of liver parenchyma mostly replaced by densely hyalinized fibrotic tissue and areas of small-to-medium sized epithelioid cells with eosinophilic and clear cytoplasm. Immunohistochemistry (IHC) demonstrated diffuse strong cytoplasmic staining of MUC4, suggesting a working diagnosis of sclerosing epithelioid fibrosarcoma (SEF)/low-grade fibromyxoid sarcoma (LGFMS). Liver explant demonstrated a well-circumscribed, nodular mass with firm, gray-white cut surface, and similar histopathology as seen in needle biopsy with no convincing evidence suggesting LGFMS. Sequencing panel revealed EWSR1::CREB3L1 gene fusion and confirmed the diagnosis of SEF. Post-operative cancer antigen 19-9 normalized 3 months after transplant; follow-up 3 and 6 months post-transplant imaging at that time showed no concern for disease recurrence.

Radical Resection of Pediatric Fibrosarcoma Is Not Associated With Survival Benefit: A Nationwide Database Analysis.

INTRODUCTION: Fibrosarcoma is one of the most common nonrhabdomyosarcoma soft tissue sarcomas in the pediatric population. Surgical resection is the cornerstone of treatment; however, optimal factors regarding the extent of fibrosarcoma resection in localized versus regional disease is poorly understood. METHODS: The Surveillance, Epidemiology, and End Results database was queried for patients who are 19 y old or younger with a diagnosis of fibrosarcoma from 1975 to 2016. Kaplan-Meier analyses were performed for disease-specific survival on clinical and pathologic variables. Multivariate analysis was performed based on significant predictors of disease-specific survival. RESULTS: There were 1290 patients (median age 13 [7-17] y) identified with fibrosarcoma. The overall survival rate at 20 y was 93%. Radical resection was performed on 22%, 40%, and 52% of patients with localized, regional, and distant Surveillance, Epidemiology, and End Results disease stage, respectively. Chemotherapy (P < 0.001), radiation (P < 0.001), histology (P < 0.001), and stage (P = 0.004) were significant predictors of increased mortality using univariate Kaplan-Meier analysis. Most patients (86%) with localized or regional stage who underwent radiation had fibrosarcomas of nondermatofibrosarcoma histology (P < 0.001). Dermatofibrosarcoma subtype comprised most radical resections (41%). Excluding distant stage, nondermatofibroma histology (hazard ratio 16.94, 95% confidence interval 3.77-76.01) and regional stage (hazard ratio 8.15, 95% confidence interval 2.93-22.69) were independent prognostic factors of mortality (both P < 0.001). Radical resection was not a significant independent prognostic indicator of survival. CONCLUSIONS: Nondermatofibrosarcoma subtype is independently associated with increased mortality. Although surgery remains the mainstay of treatment, the extent of resection is not a predictor of survival for patients with the localized and regional stage of disease.

Clinical, pathologic, and molecular analyses of superficial low-grade fibromyxoid sarcoma in two young patients: A rare and deceptive mimic of benignancy.

Low-grade fibromyxoid sarcoma (LGFMS) is a histopathologically deceptive soft tissue neoplasm with bland cytology, which is typically encountered in deep soft tissue of adults. We report two cases of superficial LGFMS in young patients (16 and 21 years old, respectively), which were difficult to diagnose on histopathologic and clinical findings alone. LGFMS commonly mimics benign neoplasms such as cellular neurothekeoma, fibromatosis, neurofibroma, and perineurioma. Malignancies included in the differential diagnosis are soft tissue neoplasms such as dermatofibrosarcoma protuberans and myxofibrosarcoma. A high degree of reported variation in pattern and cellularity among LGFMS further complicates the diagnosis. Careful examination and appropriate immunohistochemistry panels including MUC4 are essential for narrowing the differential diagnosis. Molecular studies for possible FUS translocation can confirm the diagnosis of LGFMS. Sufficient sampling and workup of these lesions are critical, especially in younger patients. Young age and superficial presentation can easily sway dermatopathologists/dermatologists toward an incorrect diagnosis of benignancy.

Congenital Infantile Fibrosarcoma Involving Pelvic Wall and Thigh Soft Tissues and Placenta, Presenting with Coagulopathy.

Infantile fibrosarcoma (IF) is a well characterized pediatric malignancy marked by gene rearrangements involving members of the NTRK family. In this report, we present a case of IF that presented in the inguinal region-proximal thigh and was initially thought to be a kaposiform hemangioendothelioma (KHE) because it presented with a bleeding diathesis thought to be Kasabach-Merritt phenomenon (KMP). Subsequently, the placental examination showed a neoplasm in the perivascular-subendothelial space of stem villi, initially thought to be myofibromatosis. Ultimately, a biopsy of the thigh mass showed IF with an NTRK3-ETV6 fusion. Subsequent FISH analysis of the placenta showed an ETV6 rearrangement confirming that it was also IF. Review of the laboratory studies suggests that disseminated intravascular coagulation may have been more likely than KMP, highlighting the difficulty in making this distinction in some cases. We believe this to be the first report of an IF presenting in a soft tissue site and the placenta, and discuss the possible mechanisms that could have allowed the IF in the leg to spread to the placenta.

Intramuscular Eyelid Myxoma.

Myxomas are a heterogeneous group of mesenchymal tumors. Soft tissue myxomas are divided into myocardial, intramuscular, juxta-articular, superficial, aggressive, and nerve sheath myxomas. Although benign, myxomas have site-specific biologic behavior and syndromic associations, which can influence prognosis and management. In addition, myxomas need to be distinguished from malignant neoplasms, such as myxofibrosarcomas, low-grade fibromyxoid sarcomas, myxoid liposarcomas, and peripheral nerve sheath tumors. While myxomas can occur throughout the body, these tumors arise more commonly in the thigh, shoulder, buttocks, and upper extremity, and less often in the head and neck. Rarely, myxomas can arise in a periocular location, typically in the conjunctiva and eyelid skin. In this case report, we present a patient with recurrent intramuscular myxoma of the eyelid and discuss the differential diagnosis and syndromic associations of this neoplasm. To our knowledge, there have been no prior reports of intramuscular myxoma of the eyelid and orbit.

An unusual fusion gene EML4-ALK in a patient with congenital mesoblastic nephroma.

Congenital mesoblastic nephroma (CMN), the most common renal tumor of infancy, is a mesenchymal neoplasm histologically classified into classic, cellular, or mixed types. Most cellular CMNs harbor a characteristic ETV6-NTRK3 fusion. Here, we report an unusual congenital mesoblastic nephroma presenting in a newborn boy with a novel EML4-ALK gene fusion revealed by Anchored Multiplex RNA Sequencing Assay. The EML4-ALK gene fusion expands the genetic spectrum implicated in the pathogenesis of congenital mesoblastic nephroma, with yet another example of kinase oncogenic activation through chromosomal rearrangement. The methylation profile of the tumor corresponds with infantile fibrosarcoma showing the biological similarity of these two entities.

A rare low-grade myofibroblastic sarcoma in lower jaw with the resemblance to benign lesions.

BACKGROUND: Low-grade myofibroblastic sarcoma (LGMS) is a rare solid infiltrative soft tissue tumor with a predilection for the head and neck region. CASE PRESENTATION: We report the diagnostic steps of a fast-growing lesion of the lower left jaw in a 45-year-old otherwise healthy woman. A first biopsy and subsequent histopathological examination showed potential differentials of a benign myofibroma, benign nodular fasciitis or an LGMS. This diagnostic overlap was a challenge for the decision of the further treatment approach. The treatment consisted of a segmental en bloc resection of the mandible including the second premolar, first and second molar. Histopathological examination of the resected tumor confirmed an LGMS. CONCLUSION: The histopathologic resemblance of LGMS to a range of benign and reactive tumors may lead to misdiagnosis and mistreatment. The rarity of LGMS explains the lack of established treatment protocols. This case shows the importance of adequate clinical decisions, expertise in the histopathology of rare tumors and interdisciplinary exchange to achieve state-of-the-art patient management.

Infantile Fibrosarcoma and Other Spindle Cell Neoplasms of Infancy. A Review of Morphologically Overlapping yet Molecularly Distinctive Entities.

BACKGROUND: Regardless of age at presentation, many soft tissue neoplasms have overlapping histopathologic and immunophenotypic features to serve as a diagnostic challenge. CASE REPORT: We reported a case of a spindle cell neoplasm in an infant, which was initially considered a vascular anomaly clinically and an eventual biopsy revealed marked inflammation with a spindle cell component that was resolved as an infantile fibrosarcoma with an ETV6 break-apart. CONCLUSION: The context of this case lead to a further consideration of various other spindle cell neoplasms arising predominantly in the soft tissues during the infancy period as defined by the first two years of age. Though sharing similar morphologic features, these tumors can be categorized into several molecular genetic groups, which have provided both diagnostic and pathogenetic insights as well as treatment options in some cases.

Fetal Mediastinal Fibrosarcoma. Report of Two Cases.

Introduction: One-third of fetal soft tissue tumors are malignant and include congenital fibrosarcoma (CF). We report two fetal CFs arising in the posterior mediastinum. Case Presentation: In case 1, the CF resulted in a mediastinal shift, extensive infiltration of the tumor around adjacent structures, pulmonary hypoplasia, pleural effusion, and rapid growth. The pregnancy was terminated. Case 2 had multiple intrathoracic masses, thoracic hypoplasia, pleural effusion, and fetal death. Both were diagnosed as fibrosarcoma at fetopsy. Discussion: Although congenital CF tends to be locally aggressive with a low metastatic rate, it tends to grow rapidly and the tumor location can affect fetal survival. In Case 1, the tumor demonstrated locally aggressive behavior whereas multiple distant metastases such as lung, liver, adrenals, and left eye were detected in Case 2. The tumor was directly responsible for intrauterine fetal demise in the second case.

The Giant Infantile Fibrosarcoma of Fetal Oropharynx and Anterior Neck.

Introduction: Infantile fibrosarcoma (IFS) usually arises in the extremities during the first 12 months of life and responds well to surgery. It is unusual in the oropharynx or the prenatal period. Case report: A giant solid mass was first detected in the oropharynx and anterior neck at 24 weeks of gestation by ultrasound and fetal MRI. An EXIT procedure with intrapartum intubation with appropriate supportive therapy was successful. The diagnosis of IFS was made postpartum, and the lesion responded to neoadjuvant chemotherapy. Conclusion: IFS may arise as early as 24 weeks of gestation. In this case, an EXIT procedure allowed postpartum diagnosis with subsequent treatment.

Primary sclerosing epithelioid fibrosarcoma of the spine: a single-institution experience.

AIMS: To present our experience on spinal sclerosing epithelioid fibrosarcoma (SEF) and review the existing literature pertaining to SEF of the spine. METHODS AND RESULTS: Six cases of spinal SEF were reviewed, and a literature search of all primary SEFs of the spine was performed. All tumours occurred in adults (median age, 41 years) and were located all along the spine, the lumbar vertebrae being the most commonly involved. All patients presented with pain that they had experienced for months. The mean tumour size at diagnosis was 52 mm. Five tumours showed a spectrum of microscopic features consistent with pure SEF, and one showed a hybrid morphology with areas of low-grade fibromyxoid sarcoma. All were diffusely and strongly positive for mucin 4. Two cases were initially misdiagnosed as epithelioid haemangioendothelioma and aggressive chondroblastoma. Fluorescence in-situ hybridisation showed rearrangements of either FUS or EWSR1 in four cases. Reverse transcription polymerase chain reaction showed the presence of FUS-CREB3L1 and EWSR1-CREB3L1 fusion transcripts in two cases and one case, respectively. Of five patients with follow-up data available, two developed one or more local recurrences and three patients had metastatic disease. Distant metastases were mainly to other osseous locations, followed by lungs and lymph nodes. At last follow-up, three patients had died of disease and one was alive with multiple metastases. CONCLUSIONS: SEF is an aggressive sarcoma that can involve the spine. It is important to recognise the spine as the primary location of SEF, in order to avoid misdiagnosis as more common primary spinal neoplasms, which can impact on therapeutic approaches.

Non-rhabdomyosarcoma soft tissue sarcomas diagnosed in patients at a young age. An overview of clinical, pathological, and molecular findings.

OBJECTIVE: Disease spectrum in pediatric sarcoma differs substantially from adults. We report a cohort of very young children with non-rhabdomyosarcoma soft tissue sarcoma (NRSTS) detailing their molecular features, treatment, and outcome. METHODS: We report features of consecutive children (age <2 years) with NRSTS (2000-2017). Archival pathological material was re-reviewed, with additional molecular techniques applied where indicated. RESULTS: Twenty-nine patients (16 females, 55%) were identified (median age 6 months; range 0-23). Most common diagnoses included infantile fibrosarcoma (IFS, n = 14, 48%), malignant rhabdoid tumor (MRT, n = 4, 14%), and undifferentiated sarcoma (n = 4, 14%). Twenty-seven of 29 (93%) had tumor molecular characterization to confirm diagnosis. Clinical presentation included a swelling/mass (n = 23, 79%). Disease extent was localized (n = 20, 69%), locoregional (n = 6, 21%), or metastatic (n = 3, 10%). Seventeen of 29 (59%) who underwent surgery achieved complete resection (R0). Other treatments included conventional chemotherapy (n = 26, 90%), molecularly targeted therapies (n = 3, 10%), and radiation (n = 5, 17%). At last follow-up (median 3 years; range 0.3-16.4), 23 (79%) were alive, disease-free and six (21%) had died of disease. All patients with IFS were alive and all those with MRT died. A cancer predisposition syndrome (CPS) was confirmed in three of 10 (30%) genetically tested patients. CONCLUSION: We recommend tumor molecular characterization in all young patients including evaluation for CPS to optimize treatment options and prognostication.

NTRK-rearranged Cervical Sarcoma: Expanding the Clinicopathologic Spectrum.

The NTRK genes (NTRK1, NTRK2, and NTRK3) encode for TrkA, TrkB, and TrkC, neurotrophic tyrosine receptor kinases which serve a variety of functions including in the regulation of pathways involved in carcinogenesis. A number of reports have described NTRK gene fusions in a variety of adult and pediatric tumor types from various organ systems including the central nervous system, thyroid gland, breast, and soft tissue. NTRK-rearranged uterine sarcomas are a recently described group of tumors which occur in both the uterine corpus and cervix, tend to morphologically resemble fibrosarcoma, and may behave aggressively, although data is limited given the newly recognized nature and thus relative rarity of these tumors. Herein, we present the case of a cervical sarcoma with SPECC1L-NTRK3 fusion (detected with Illumina RNA Fusion Panel), prospectively diagnosed at the time of cervical biopsy and subsequently treated with hysterectomy. The clinical presentation, radiologic findings, morphologic features, and immunohistochemical profile of this case will be reviewed and compared with the body of existing literature to date. Identification of NTRK-rearranged neoplasms is important as targeted therapy in the form of NTRK inhibitors has recently become widely available.

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.

Sclerosing Epithelioid Fibrosarcoma of the Kidney: First Reported Case in a Young Child.

Sclerosing epithelioid fibrosarcoma (SEF) is a rare variant of fibrosarcoma primarily arising in the deep soft tissue of the extremities and trunk. Despite having the morphologic appearance of a low-grade sarcoma, it generally has an aggressive clinical course with frequent local recurrences and distant metastases. It typically occurs in middle aged adults and is characterized by immunoexpression of MUC4 and recurrent gene fusions, most commonly EWSR1-CREB3L1. We report a primary renal SEF in a 4-year-old male. To our knowledge, this is the youngest patient reported with SEF and the second case of SEF in a pre-adolescent child. It is the eleventh reported case of primary renal SEF in the literature. While SEF arising in visceral organs is rare, the kidney is the most common primary site of any visceral organ. This case demonstrates SEF can occur in pre-adolescents, is an important consideration when evaluating sarcomas in young children, and should be considered in the differential diagnosis for primary renal tumors.

Differential diagnostic features between congenital haemangioma, KHE, and congenital fibrosarcoma: a single-centre experience.

Congenital haemangioma (CH) is a rare benign vascular tumour presenting at birth with excellent prognosis. Usually, CH regresses without treatment within the first few months of life. Kaposiform Haemangioendothelioma (KHE) is another type of vascular tumours that has been described as benign with locally aggressive potential. Although the diagnosis of vascular tumours is usually straightforward based on typical clinical presentation, yet some confusing similarities may exist with congenital sarcomas.Conclusion: Data of cases managed at the vascular anomaly clinic during the period 2015 through 2019 were retrospectively analysed. The study included three groups of patients: cases diagnosed as congenital haemangioma (9 cases), cases of Kaposiform Haemangioendothelioma who presented in the neonatal period (7 cases), as well as cases of congenital fibrosarcoma (4 cases) that were referred to the vascular anomaly clinic because of apparent similarity with vascular tumours. The hallmark of the study was to compare clinical and imaging features in the three groups to facilitate differentiation and remove diagnostic confusion when managing these rare cases in the future. What is Known: • Congenital haemangioma is a rare benign vascular tumour presenting at birth. • Kaposiform Haemangioendothelioma is another type of vascular tumours that has been described as benign with locally aggressive potential. What is New: • Confusing similarities may exist between vascular tumours and congenital sarcomas.