Successful treatment of lipofibromatosis-like neural tumor of the lumbar spine with an NTRK-fusion inhibitor

Current management of neurotrophic receptor tyrosine kinase fusion-positive sarcoma: an updated review

In recent years, pembrolizumab has demonstrated significant efficacy in treating tumors characterized by a high tumor mutational burden and high microsatellite instability. Tropomyosin receptor kinase (TRK) inhibitors have shown considerable efficacy against tumors harboring neurotrophic receptor tyrosine kinase (NTRK) fusion genes, highlighting the growing importance of personalized medicine in cancer treatment. Advanced sequencing technologies enable the rapid analysis of numerous genetic abnormalities in tumors, facilitating the identification of patients with positive biomarkers. These advances have increased the likelihood of providing effective, tailored treatments. NTRK fusion genes are present in various cancer types, including sarcomas, and the TRK inhibitors larotrectinib and entrectinib have been effectively used for these malignancies. Consequently, the treatment outcomes for NTRK fusion-positive tumors have improved significantly, reflecting a shift toward more personalized therapeutic approaches. This review focuses on NTRK fusion-positive sarcomas and comprehensively evaluates their epidemiology, clinical features, and radiological and histological characteristics. We also investigated the treatment landscape, including the latest methodologies involving TRK inhibitors, and discussed the long-term efficacy of these inhibitors, and their optimal order of use. Notably, larotrectinib has demonstrated a high response rate in infantile fibrosarcoma, and its efficacy has been confirmed even in advanced cases. However, further research is warranted to optimize treatment duration and subsequent management strategies. The accumulation of clinical cases worldwide will play a pivotal role in refining the treatment approaches for tumors associated with NTRK fusion genes.

Case Report: Misdiagnosis of a lipofibromatosis-like neural tumor of the dorsal skin as dermatofibrosarcoma protuberans

Background

Lipofibromatosis-like neural tumors (LPF-NT), which have only recently been established, are intermediate soft tissue tumors with neurotrophic tropomyosin receptor kinase 1 (NTRK1) gene alterations and are typically misdiagnosed as dermatofibrosarcoma protuberans, low-grade malignant peripheral nerve sheath tumors, or spindle cell lipoma due to their histopathological and immunohistochemical expression of CD34 and S-100.

Case presentation

The patient was admitted to our hospital with a painless back mass that had appeared more than 4 years prior to admission. Physical examination revealed a subcutaneous mass on the back, approximately 1.5 cm in diameter and protruding into the skin, with clear boundaries and no tenderness. The tumor was surgically resected. The postoperative pathological results suggested a spindle cell soft tissue tumor, and dermatofibrosarcoma protuberan was initially considered. After consultation at a provincial hospital, the patient was diagnosed with a cutaneous lipofibromatosis-like neural tumor of the back. A second extended resection was then performed. Intraoperative rapid freezing examination revealed negative incision margins.

Conclusion

Histological and immunohistochemical detections aid in the differential diagnosis of LPF-NTs. Complete surgical resection is the preferred treatment for LPF-NTs.

Imaging characterization of paediatric tumours with the neurotrophic tyrosine receptor kinase fusion transcript

OBJECTIVES

The neurotrophic tyrosine receptor kinase (NTRK) fusion transcript (FT) is a major genetic landmark of infantile fibrosarcoma (IFS) and cellular congenital mesoblastic nephroma (cCMN) but is also described in other tumours. The recent availability of NTRK-targeted drugs enhances the need for better identification. We aimed to describe the anatomic locations and imaging features of tumours with NTRK-FT in children.

CASE SERIES

Imaging characteristics of NTRK-FT tumours of 41 children (median age: 4 months; 63% <1 year old; range: 0-188) managed between 2001 and 2019 were retrospectively analysed. The tumours were located in the soft tissues (n = 24, including 19 IFS), kidneys (n = 9, including 8 cCMN), central nervous system (CNS) (n = 5), lung (n = 2), and bone (n = 1). The tumours were frequently deep-located (93%) and heterogeneous (71%) with necrotic (53%) or haemorrhagic components (29%). Although inconstant, enlarged intratumoural vessels were a recurrent finding (70%) with an irregular distribution (63%) in the most frequent anatomical locations.

CONCLUSION

Paediatric NTRK-FT tumours mainly occur in infants with very variable histotypes and locations. Rich and irregular intra-tumoural vascularization are recurrent findings.

ADVANCES IN KNOWLEDGE

Apart from IFS of soft tissues and cCMN of the kidneys, others NTRK-FT tumours locations have to be known, as CNS tumours. Better knowledge of the imaging characteristics may help guide the pathological and biological identification.

Detection of Novel Tyrosine Kinase Fusion Genes as Potential Therapeutic Targets in Bone and Soft Tissue Sarcomas Using DNA/RNA-based Clinical Sequencing

BACKGROUND

Approximately 1% of clinically treatable tyrosine kinase fusions, including anaplastic lymphoma kinase, neurotrophic tyrosine receptor kinase, RET proto-oncogene, and ROS proto-oncogene 1, have been identified in soft tissue sarcomas via comprehensive genome profiling based on DNA sequencing. Histologic tumor-specific fusion genes have been reported in approximately 20% of soft tissue sarcomas; however, unlike tyrosine kinase fusion genes, these fusions cannot be directly targeted in therapy. Approximately 80% of tumor-specific fusion-negative sarcomas, including myxofibrosarcoma and leiomyosarcoma, that are defined in complex karyotype sarcomas remain genetically uncharacterized; this mutually exclusive pattern of mutations suggests that other mutually exclusive driver oncogenes are yet to be discovered. Tumor-specific, fusion-negative sarcomas may be associated with unique translocations, and oncogenic fusion genes, including tyrosine kinase fusions, may have been overlooked in these sarcomas.

QUESTIONS/PURPOSES

(1) Can DNA- or RNA-based analysis reveal any characteristic gene alterations in bone and soft tissue sarcomas? (2) Can useful and potential tyrosine kinase fusions in tumors from tumor-specific, fusion-negative sarcomas be detected using an RNA-based screening system? (3) Do the identified potential fusion tumors, especially in neurotrophic tyrosine receptor kinase gene fusions in bone sarcoma, transform cells and respond to targeted drug treatment in in vitro assays? (4) Can the identified tyrosine kinase fusion genes in sarcomas be useful therapeutic targets?

METHODS

Between 2017 and 2020, we treated 100 patients for bone and soft tissue sarcomas at five institutions. Any biopsy or surgery from which a specimen could be obtained was included as potentially eligible. Ninety percent (90 patients) of patients were eligible; a further 8% (8 patients) were excluded because they were either lost to follow-up or their diagnosis was changed, leaving 82% (82 patients) for analysis here. To answer our first and second questions regarding gene alterations and potential tyrosine kinase fusions in eight bone and 74 soft tissue sarcomas, we used the TruSight Tumor 170 assay to detect mutations, copy number variations, and gene fusions in the samples. To answer our third question, we performed functional analyses involving in vitro assays to determine whether the identified tyrosine kinase fusions were associated with oncogenic abilities and drug responses. Finally, to determine usefulness as therapeutic targets, two pediatric patients harboring an NTRK fusion and an ALK fusion were treated with tyrosine kinase inhibitors in clinical trials.

RESULTS

DNA/RNA-based analysis demonstrated characteristic alterations in bone and soft tissue sarcomas; DNA-based analyses detected TP53 and copy number alterations of MDM2 and CDK4 . These single-nucleotide variants and copy number variations were enriched in specific fusion-negative sarcomas. RNA-based screening detected fusion genes in 24% (20 of 82) of patients. Useful potential fusions were detected in 19% (11 of 58) of tumor-specific fusion-negative sarcomas, with nine of these patients harboring tyrosine kinase fusion genes; five of these patients had in-frame tyrosine kinase fusion genes ( STRN3-NTRK3, VWC2-EGFR, ICK-KDR, FOXP2-MET , and CEP290-MET ) with unknown pathologic significance. The functional analysis revealed that STRN3-NTRK3 rearrangement that was identified in bone had a strong transforming potential in 3T3 cells, and that STRN3-NTRK3 -positive cells were sensitive to larotrectinib in vitro. To confirm the usefulness of identified tyrosine kinase fusion genes as therapeutic targets, patients with well-characterized LMNA-NTRK1 and CLTC-ALK fusions were treated with tyrosine kinase inhibitors in clinical trials, and a complete response was achieved.

CONCLUSION

We identified useful potential therapeutic targets for tyrosine kinase fusions in bone and soft tissue sarcomas using RNA-based analysis. We successfully identified STRN3-NTRK3 fusion in a patient with leiomyosarcoma of bone and determined the malignant potential of this fusion gene via functional analyses and drug effects. In light of these discoveries, comprehensive genome profiling should be considered even if the sarcoma is a bone sarcoma. There seem to be some limitations regarding current DNA-based comprehensive genome profiling tests, and it is important to use RNA testing for proper diagnosis and accurate identification of fusion genes. Studies on more patients, validation of results, and further functional analysis of unknown tyrosine kinase fusion genes are required to establish future treatments.

CLINICAL RELEVANCE

DNA- and RNA-based screening systems may be useful for detecting tyrosine kinase fusion genes in specific fusion-negative sarcomas and identifying key therapeutic targets, leading to possible breakthroughs in the treatment of bone and soft tissue sarcomas. Given that current DNA sequencing misses fusion genes, RNA-based screening systems should be widely considered as a worldwide test for sarcoma. If standard treatments such as chemotherapy are not effective, or even if the sarcoma is of bone, RNA sequencing should be considered to identify as many therapeutic targets as possible.

NTRK-rearranged spindle cell neoplasms: a clinicopathological and molecular study of 13 cases with peculiar characteristics at one of the largest institutions in China

NTRK-rearranged spindle cell neoplasms (NTRK-RSCNs) represent an emerging group of rare tumours defined using molecular means. To the best of our knowledge, there have been no large series of reports about this tumour in the Chinese population in English full-text articles. Herein, we present 13 NTRK-RSCNs with peculiar characteristics. Ten of the 13 (77%) patients were children without sex differences. The tumour locations included six trunks, four extremities, two recta, and one small bowel. The histological morphology included four lipofibromatosis-like neural tumour (LPF-NT)-like, eight malignant peripheral nerve sheath tumours (MPNST)/fibrosarcoma-like, and one extremely rare myxofibrosarcoma-like pattern. Immunohistochemically, all cases were CD34, pan-TRK and TRK-A positive, SOX-10 negative, and H3K27me3 intact. S-100 protein expression was identified in 11 of 13 (85%) cases. Genetically, NTRK1 rearrangements were considered positive (7/13, 54%) or suspicious for positivity (6/13, 46%) by fluorescence in situ hybridisation. Next-generation sequencing and Sanger sequencing confirmed NTRK1 fusions with a variety of partner genes, including five LMNA, three TPM3, one SQSTM1, three novel CPSF6, IGR (downstream PMVK), and GAS2L1 genes. Interestingly, the last tumour concurrently harboured a second EWSR1-PBX1 fusion, which has never been reported. Four patients developed local recurrence and two of them suffered metastasis. In our study, NTRK-RSCNs had peculiar fusions that displayed unusual or complicated clinicopathological features. Histological clues and IHC helped streamline a small subset of potential candidates. Although FISH is a powerful technology for identifying NTRK rearrangements, RNA-/DNA-based NGS is recommended for highly suspected cases in which FISH signal patterns are not discernible as classic positive patterns, particularly if targeted therapy is considered.

NTRK-rearranged spindle cell neoplasms are ubiquitous tumours of myofibroblastic lineage with a distinct methylation class

AIMS

NTRK gene fusions have been described in a wide variety of central nervous system (CNS) and soft tissue tumours, including the provisional tumour type 'spindle cell neoplasm, NTRK-rearranged' (SCN-NTRK), added to the 2020 World Health Organisation Classification of Soft Tissue Tumours. Because of histopathological and molecular overlaps with other soft tissue entities, controversy remains concerning the lineage and terminology of SCN-NTRK.

METHODS AND RESULTS

This study included 16 mesenchymal tumours displaying kinase gene fusions (NTRK fusions and one MET fusion) initially diagnosed as infantile fibrosarcomas (IFS), SCN-NTRK and adult-type fibrosarcomas from the soft tissue, viscera and CNS. We used immunohistochemistry, DNA methylation profiling, whole RNA-sequencing and ultrastructural analysis to characterise them. Unsupervised t-distributed stochastic neighbour embedding analysis showed that 11 cases (two CNS tumours and nine extra-CNS) formed a unique and new methylation cluster, while all tumours but one, initially diagnosed as IFS, clustered in a distinct methylation class. All the tumours except one formed a single cluster within the hierarchical clustering of whole RNA-sequencing data. Tumours from the novel methylation class co-expressed CD34 and S100, had variable histopathological grades and frequently displayed a CDKN2A deletion. Ultrastructural analyses evidenced a myofibroblastic differentiation.

CONCLUSIONS

Our findings confirm that SCN-NTRK share similar features in adults and children and in all locations combine an infiltrative pattern, distinct epigenetic and transcriptomic profiles, and ultrastructural evidence of a myofibroblastic lineage. Further studies may support the use of new terminology to better describe their myofibroblastic nature.

Lipofibromatosis-like neural tumors: Report of a case and review of 73 reported cases

Lipofibromatosis-like neural tumors (LPF-NTs) are a recently discovered group of spindle cell tumors defined by the presence of a lipofibromatosis-like pattern, CD34 and/or S100 reactivity, and frequent neurotrophic receptor tyrosine kinase 1 (NTRK1) gene rearrangements. As new cases emerge, the spectrum of features observed in LPF-NTs continues to evolve. Here we describe the case of an 11-year-old with LPF-NT with a dermatofibrosarcoma protuberans-like honeycomb pattern, CD34 and S100 co-expression, and an NTRK1 rearrangement. We also review the clinical and molecular features of the 73 cases of LPF-NT previously described in the literature.

Implementation of multi-mode nursing insulation program for patients receiving surgery for spine tumor: a propensity score-matched analysis

BACKGROUND

Spinal tumor surgery usually involved long operation time, large area of soft tissue resection and long wound, and was prone to hypothermia during the operation. Therefore, actively promoting insulation and optimizing the intraoperative insulation program have great potential in reducing the incidence of hypothermia and reducing the incidence of postoperative complications. In this study, we compared patients who did not implement multi-mode nursing insulation program (MNIP) with those who implemented MNIP, observing and comparing clinical outcomes, and complications in both groups, with the aim of developing an optimal management plan for the preoperative, intraoperative, and postoperative periods, respectively.

METHODS

We selected 2 periods of 1 year, before (n = 120 patients) and after MINP implementation (n = 120 patients). Data were collected on patient demographics, operative, perioperative details, temperature changes, anesthesia recovery effect, incidence of postoperative wound infection, length of hospital stay and complications. PS analyses were used for dealing with confounding bias in this retrospective observational study.

RESULTS

After PS matching, the outcomes of 120 well-balanced pairs of patients were compared (No-MNIP vs MNIP). There was no significant difference concerning the satisfaction survey. The results indicated that the MNIP had better insulation effect at 90 min, 120 min, 150 min after anesthesia induction and after surgery. There were 16 cases of complications in the No-MNIP group and 5 cases in the MNIP group postoperative, which have significant statistical difference.

CONCLUSION

In this study, the incidence of intraoperative hypothermia was effectively reduced by adopting the multi-mode insulation scheme, thus reducing the incidence of incision infection and shortening the length of hospital stay of patients.

Primary extradural tumors of the spinal column: A comprehensive treatment guide for the spine surgeon based on the 5th Edition of the World Health Organization bone and soft-tissue tumor classification

BACKGROUND

In 2020, the World Health Organization (WHO) published the 5th version of the soft tissue and bone tumor classification. Based on this novel classification system, we reviewed the current knowledge on all tumor entities with spinal manifestations, their biologic behavior, and most importantly the appropriate treatment options as well as surgical approaches.

METHODS

All tumor entities were extracted from the WHO Soft-Tissue and Bone Tumor Classification (5th Edition). PubMed and Google Scholar were searched for the published cases of spinal tumor manifestations for each entity, and the following characteristics were extracted: Growth pattern, ability to metastasize, peak age, incidence, treatment, type of surgical resection indicated, recurrence rate, risk factors, 5-year survival rate, key molecular or genetic alterations, and possible associated tumor syndromes. Surgical treatment strategies as well as nonsurgical treatment recommendations are presented based on the biologic behavior of each lesion.

RESULTS

Out of 163 primary tumor entities of bone and soft tissue, 92 lesions have been reported along the spinal axis. Of these 92 entities, 54 have the potential to metastasize. The peak age ranges from conatal lesions to 72 years. For each tumor entity, we present recommended surgical treatment strategies based on the ability to locally destruct tissue, to grow, recur after resection, undergo malignant transformation as well as survival rates. In addition, potential systemic treatment recommendations for each tumor entity are outlined.

CONCLUSION

Based on the 5th Edition of the WHO bone and soft tumor classification, we identified 92 out of 163 tumor entities, which potentially can have spinal manifestations. Exact preoperative tissue diagnosis and interdisciplinary case discussions are crucial. Surgical resection is indicated in a significant subset of patients and has to be tailored to the specific biologic behavior of the targeted tumor entity based on the considerations outlined in detail in this article.

Update on Superficial Spindle Cell Mesenchymal Tumors in Children

The diagnosis of cutaneous and subcutaneous spindle cell neoplasms in children is often challenging and has potential therapeutic and prognostic implications. Although correctly diagnosing dermatofibrosarcoma protuberans and infantile fibrosarcoma is paramount, pathologists should not ignore a number of diagnostic pitfalls linked to mostly rare tumors with completely different clinical outcomes. In the last decade, a spectrum of novel entities has been described; information from molecular biology has helped to shape this new landscape for spindle cell tumors. Here, we review the most noteworthy neoplasms in this spectrum, with a focus on their histological similarities: fibroblastic connective tissue nevus, medallion-like dermal dendrocyte hamartoma, or plaque-like CD34-positive dermal fibroma, which share features with fibrous hamartoma of infancy; lipofibromatosis and lipofibromatosis-like neural tumor; and plexiform myofibroblastoma, a recently described neoplasm that should be distinguished from plexiform fibrohistiocytic tumor. These tumors also have genetic similarities, particularly gene rearrangements involving NTRK3 or NTRK1. These genetic features are not only essential for the differential diagnosis of infantile fibrosarcoma but are also of diagnostic value for lipofibromatosis-like neural tumors. The more recently described RET, RAF1, and BRAF gene fusions are also discussed.

Interstitial Deletions Generating Fusion Genes

A fusion gene is the physical juxtaposition of two different genes resulting in a structure consisting of the head of one gene and the tail of the other. Gene fusion is often a primary neoplasia-inducing event in leukemias, lymphomas, solid malignancies as well as benign tumors. Knowledge about fusion genes is crucial not only for our understanding of tumorigenesis, but also for the diagnosis, prognostication, and treatment of cancer. Balanced chromosomal rearrangements, in particular translocations and inversions, are the most frequent genetic events leading to the generation of fusion genes. In the present review, we summarize the existing knowledge on chromosome deletions as a mechanism for fusion gene formation. Such deletions are mostly submicroscopic and, hence, not detected by cytogenetic analyses but by array comparative genome hybridization (aCGH) and/or high throughput sequencing (HTS). They are found across the genome in a variety of neoplasias. As tumors are increasingly analyzed using aCGH and HTS, it is likely that more interstitial deletions giving rise to fusion genes will be found, significantly impacting our understanding and treatment of cancer.

Staging and Classification of Primary Musculoskeletal Bone and Soft Tissue Tumors Based on 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 has resulted in newly designated lesions, reclassification of lesion categories, and improved specificity of diagnosis. While 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 approaching primary musculoskeletal neoplasms through a multidisciplinary approach with colleagues in pathology, orthopedic oncology, radiation oncology, and medical oncology, radiologists may promote improved diagnosis, treatment, and outcomes.