Molecular characterization of inflammatory myofibroblastic tumors with frequent ALK and ROS1 gene fusions and rare novel RET rearrangement

Insights into inflammatory myofibroblastic tumor: A complex and challenging diagnosis

Inflammatory myofibroblastic tumor (IMT), also known as inflammatory pseudotumor or plasma cell granuloma, is an uncommon soft tissue tumor of mesenchymal origin with low to intermediate malignant potential. IMTs are most commonly located in the lung, abdomen/pelvis, or retroperitoneum, primarily affecting children and young adults. Although metastasis is rare, IMTs can recur after surgical resection, as oftentimes resection is limited due to infiltration with surrounding tissue. Here, we present a challenging case of IMT in a 22-year-old male who presented with chest pain and shortness of breath. Extensive diagnostic workup, including multiple biopsies and imaging studies, raised suspicion of malignancy, though initial biopsies failed to confirm a diagnosis. This case highlights the diagnostic difficulties and the importance of a coordinated approach in the diagnosis and management of IMT.

Clinicopathological and Molecular Features of Primary Inflammatory Myofibroblastic Tumor in Nasal Cavity and Paranasal Sinuses

Background

Inflammatory myofibroblastic tumor (IMT) in the nasal cavity and sinuses is rare and has special clinical and pathological characteristics with poor prognosis. This study aimed to investigate the clinicopathological and molecular features of primary IMT in the nasal cavity and paranasal sinuses.

Methods

The clinical features, histopathological findings, immunohistochemical findings and results of molecular genetic examination were retrospectively analyzed in 25 patients who were diagnosed with IMT in the nasal cavity and paranasal sinuses.

Results

Tumor tissues were mainly composed of obese spindle-shaped myofibroblasts, fibroblasts, and chronic inflammatory cells. The inflammatory cells included plasma cells, lymphocytes, eosinophils, foam histiocytes and multinuclear giant cells. Immunohistochemical staining showed the tumor was positive to anaplastic lymphoma kinase (ALK) in two patients. ALK fusion mutation was detected by PCR in only 1 patient.

Conclusion

Nasal and paranasal sinus IMTs are rare, exhibit histopathological diversity with low specificity, and require careful differentiation from inflammatory and autoimmune disorders. These tumors demonstrate a worse prognosis compared to IMTs in other anatomic locations, along with a significantly lower rate of ALK gene rearrangement. Identifying molecular target alterations can enhance precision diagnosis and targeted therapeutic strategies.

Inflammatory Myofibroblastic Tumor: An Updated Review

Inflammatory myofibroblastic tumor (IMT) is a rare neoplasm that is characterized by a proliferation of myofibroblastic and fibroblastic spindle cells, accompanied by an inflammatory infiltrate that is abundant in plasma cells, lymphocytes, and eosinophils. IMT can arise in various anatomical locations but most commonly occurs in the abdominal cavity, retroperitoneum, and lung, particularly in children and young adults. IMT typically demonstrates local invasion or recurrence, whereas metastasis is rare. IMTs pose a diagnostic challenge because of their overlapping morphological characteristics with a heterogeneous group of nonneoplastic and neoplastic lesions. Precise diagnosis is crucial for optimal management and accurate prognostication. Despite recent advancements in IMT diagnosis and treatment, its biological complexity and clinical management remain challenging due to significant histological heterogeneity and molecular genetic diversity. This review provides comprehensive updates on the clinical, molecular, and pathological characteristics of IMT, highlighting the diagnostic approaches and key differential diagnoses.

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.

Inflammatory myofibroblastic tumor in the liver after bone marrow transplantation: case report and literature review

Introduction

Inflammatory myofibroblastic tumor (IMT) is a rare low-grade malignant neoplasm in the liver. Timely diagnosis and treatment of IMT are challenging due to its atypical symptoms and imaging results.

Case report

We report a 46-year-old woman who presented to our hospital with persistent hyperpyrexia and discomfort in the right upper abdomen for 2 months post bone marrow transplantation. Radiological findings revealed a space-occupying lesion of uncertain nature in the liver. Since the histological examination of the biopsy specimen indicated IMT, she underwent surgical resection. Subsequently, the postoperative pathology confirmed the diagnosis of IMT. The patient's febrile condition subsided after the surgery. A magnetic resonance imaging (MRI) scan performed 8 months later showed no signs of recurrence.

Conclusion

IMTs are caused by genetic rearrangements. Diagnosing IMT can be challenging especially in this case as we had to differentiate the tumor from inflammatory diseases associated with bone marrow transplantation. Hence, a thorough pathological immunohistochemical examination is required to confirm its diagnosis. Local IMTs should be treated with radical surgical resection. In cases of distant metastasis or incomplete resection cases, chemotherapy, targeted therapy, or immunotherapy can be utilized. Regular follow-up is crucial for improving the patient's survival rate.

Methotrexate resistance and its regulatory mechanisms in pediatric tumors and beyond

Methotrexate (MTX) is a critical antimetabolite drug in treating various pediatric diseases, including acute lymphoblastic leukemia (ALL), non-Hodgkin lymphoma (NHL), brain tumors, osteosarcoma, inflammatory myofibroblastic tumor (IMT), juvenile scleroderma (JS), and juvenile idiopathic arthritis (JIA). MTX acts as a folate antagonist by inhibiting dihydrofolate reductase (DHFR), an enzyme essential for the synthesis of tetrahydrofolate. This disruption impairs DNA synthesis, repair, and cellular replication, particularly affecting rapidly dividing cells. Despite its efficacy, MTX resistance poses significant challenges, particularly in pediatric oncology, where it undermines the ability to achieve sustained therapeutic effects, resulting in reduced therapeutic efficacy and poor prognosis. The mechanisms of MTX resistance encompassed reduced enzyme activity pivotal for MTX metabolism, enhanced expression of efflux transporters, genetic variations, and alterations in signaling pathways. Multifaceted strategies have been explored to overcome MTX resistance. Combination therapies with ginger extract, gold nanoparticles, and arsenic trioxide (ATO) have been investigated to augment MTX's cytotoxic effects. Synergies with mTOR inhibitors and MDM2 inhibitors have demonstrated enhanced outcomes in ALL. In JIA, targeting ATP-binding cassette (ABC) transporters and modulating transforming growth factor‑β (TGF-β) signaling pathways have emerged as promising approaches. For osteosarcoma, emphasis on autophagy pathways and non-coding RNAs influencing chemotherapy sensitivity could enhance MTX effectiveness. This review delineates MTX's therapeutic roles, elucidates its resistance mechanisms, and discusses current and potential strategies for managing MTX resistance to bolster treatment effectiveness in pediatric tumors and other diseases. This knowledge base could underpin further research and development of personalized treatments to optimize MTX's clinical benefits.

Mesenteric inflammatory myofibroblastic tumor (IMT), a rare neoplasm in a pediatric patient: imaging findings and literature review

Inflammatory myofibroblastic tumors (IMTs) are rare neoplasms commonly classified as having "intermediate malignancy" due to their unique clinical, pathological, and molecular features. These tumors can exhibit aggressive biological behavior, including local invasion, recurrence, and, on rare occasions, distant metastasis. IMTs may arise in various anatomical locations, with the lung, mesentery, and omentum being the most frequent sites. Although IMTs can occur at any age, they are more commonly diagnosed in children and young adults. Their clinical manifestations and imaging findings are often nonspecific and may resemble malignant pathology, making diagnosis challenging. Moreover, the histopathological characteristics of IMTs can overlap with those of other conditions. In this report, we present a case of multicentric abdominal IMT in a pediatric patient and review the imaging features of abdominal IMTs in children, as documented in the limited number of available cases. Accurate differential diagnosis requires a comprehensive understanding of both the clinical presentation and radiographic features of these tumors. Radiologists should be familiar with the distinctive imaging characteristics of IMTs to ensure that this rare pathology is considered in the differential diagnosis of any abdominal mass in pediatric patients.

Inflammatory myofibroblastic tumor of the adrenal gland: A case report

INTRODUCTION AND IMPORTANCE

Inflammatory myofibroblastic tumor (IMT) is an extremely rare sarcoma mainly reported in the lung. The adrenal gland, however, is an extremely rare site of occurrence. Herein, we report a case of a large adrenal mass with no contributory imaging features presenting a challenging pathological diagnosis.

CASE PRESENTATION

A healthy 32-year-old male patient, with no personal nor family history, presented with loss of body weight and condition developing for two months. Physical examination revealed no abnormalities with a soft and depressible abdomen and absence of palpable lump. Circulating Chromogranin A and catecholamine metabolites were within normal range. The preoperative imaging features were noncontributory. The pathological examination on biopsy specimen concluded to a spindle cell proliferation set in a chronically inflamed background suggesting the diagnosis of IMT. The patient, subsequently, underwent radical nephrectomy unveiling a 25 cm adrenal mass. Pathological findings on resection specimen confirmed the diagnosis of IMT of the left adrenal gland.

CLINICAL DISCUSSION

Due to their rarity in the adrenal gland and their noncontributory radiological features, IMTs are typically not considered as a potential diagnosis in this location. As a result, this condition is often underdiagnosed. In this setting, suspicion for IMT should be raised when spindle cell histology is observed.

CONCLUSION

It is fundamental for practicians to keep this entity in mind as the treatment consists of complete tumor extirpation. The latter being the only guarantee of recurrence free follow up.

Pediatric Genitourinary Tumors: The Developmental Angle

Pediatric cancer is relatively rare compared to cancer in adults. Most pediatric neoplasms affect the hemopoietic and central nervous systems. Of the solid extracranial tumors, renal and genitourinary lesions are among the most frequent pediatric neoplasms. Wilms tumors (nephroblastomas) and their variants predominate. Others are less frequent, and their rarity leads to significant diagnostic challenges. This review presents the most important points for diagnosis using histopathological, immunophenotypical, and molecular novel information on the most important renal and genitourinary pediatric neoplasms.

Mesenchymal Tumors of the Tubular Gastrointestinal Tract (Non-GIST): The GI Pathologist's Approach

Mesenchymal neoplasms of the gastrointestinal tract are rare compared with epithelial lesions. However, over the past few decades, the increasing volume of gastrointestinal endoscopy has expedited the recognition of several novel entities with varying clinical significance. Its spectrum extends from reactive changes and benign neoplasms to highly aggressive sarcomas. At the malignant end of the spectrum, the importance of correctly diagnosing these tumors is underscored by the specific therapeutic implications available for some tumor types (eg, tyrosine kinase inhibitors for gastrointestinal stromal tumors) that allow personalized treatments. Benign lesions frequently surface among routine polypectomy specimens, sometimes offering diagnostic challenges. However, precise classification is the only way to avoid prognostic uncertainty and overtreatment, and to recognize possible syndromic associations. Hereby, we offer a pragmatic review of the topic from the gastrointestinal pathologist's perspective, who, although more accustomed to epithelial neoplasms, can use an algorithmic approach to diagnose mesenchymal entities successfully.

Partial response to lorlatinib in thoracic inflammatory myofibroblastic tumor harboring complex and rare ALK fusions: a case report

Background

Targeted therapy has dramatically altered the treatment paradigm for some patients with inflammatory myofibroblastic tumor (IMT) that possesses specific molecular aberrations. IMT is an exceedingly rare type of sarcoma, with about 50% of cases featuring anaplastic lymphoma kinase (ALK) gene rearrangements. The treatment of IMT with ALK fusions using ALK tyrosine kinase inhibitors (TKIs) has become increasingly common. However, until now, there is a lack of evidence supporting the efficacy of third-generation ALK-TKIs in this disease category.

Case Description

Here, we report the first case of a patient with advanced IMT harboring the EML4-ALK fusion gene along with two rare ALK fusion genes: PLB1-ALK, which has only been reported in two cases of lung adenocarcinoma and large cell neuroendocrine carcinoma, and unreported ALMS1-ALK. The patient achieved partial response (PR) following first-line treatment with lorlatinib and subsequently underwent successful surgical intervention.

Conclusions

This is the inaugural case of a third-generation ALK-TKI achieving therapeutic success in advanced IMT with complex ALK rearrangements, including rare and previously uncharacterized fusion subtypes. Although the biological functions of these two rare ALK fusions still need to be confirmed, this case underscores the dependency of ALK-rearranged IMT on ALK-mediated signaling, suggesting that third-generation ALK-TKIs may offer an optimal targeted therapeutic strategy for ALK-dependent mesenchymal tumor subtypes.

Inflammatory myofibroblastic tumors in children: clinical characteristics and treatment outcomes with a focus on targeted therapies

BACKGROUND

Inflammatory myofibroblastic tumors (IMTs) are rare neoplasms in children. Traditionally, surgical resection has been the primary treatment modality with limited efficacy reported for conventional chemotherapy and radiation therapy. Recently, targeted therapies have emerged as potential options for selected cases. This study aimed to evaluate the demographic, clinical, laboratory, and radiological characteristics, as well as treatment outcomes, in children diagnosed with IMTs.

METHODS

This study involved a retrospective review of medical records for eight children diagnosed with IMTs between 1990 and 2022. We collected demographic, clinical, laboratory, and radiological data, as well as treatment outcomes. Data on tumor characteristics, surgical procedures, and chemotherapy or targeted therapy treatments were extracted.

RESULTS

The mean age at diagnosis was 9 years. None presented with metastatic disease at the time of diagnosis. Anaplastic lymphoma kinase (ALK) positivity was identified in tumor tissue from five patients. Among the six patients who underwent surgical resection, three achieved negative surgical margins. Of the three patients with positive surgical margins, one underwent re-resection, local and metastatic recurrences were noted in another, and one was started on crizotinib. A patient with an inoperable tumor at diagnosis was initiated on crizotinib and achieved complete remission. Ceritinib was administered to a patient with YWHAE-ROS fusion, resulting in more than 90% reduction in tumor volume. The median follow-up time was 67.5 months. The five-year overall survival and event-free survival rates for the cohort were 85.7% and 72.9%, respectively.

CONCLUSIONS

While surgical resection remains the cornerstone of treatment for IMTs, favorable outcomes can be achieved with chemotherapy and targeted therapies in selected cases. Increasing the utilization of targeted therapies may be beneficial, particularly through molecular studies aimed at minimizing the side effects associated with conventional chemotherapy.

Mesenchymal Tumors of the Liver: An Update Review

Hepatic mesenchymal tumors (HMTs) are non-epithelial benign and malignant tumors with or without specific mesenchymal cell differentiation. They are relatively uncommon. Except for mesenchymal hamartoma, calcified nested stromal-epithelial tumor, and embryonal sarcoma, most mesenchymal lesions are not specific to the liver. Pathologists face challenges in diagnosing HMTs due to their diverse morphologies and phenotypic variations. Accurate diagnosis is critical for directing appropriate patient care and predicting outcomes. This review focuses on mesenchymal tumors with a relative predilection for the liver, including vascular and non-vascular mesenchymal neoplasms. It provides a thorough and up-to-date overview, concentrating on clinical and pathological features, differential diagnosis, and diagnostic approaches.

PDGFRA::USP8 Fusion in a Cutaneous Inflammatory Myofibroblastic Tumor, Highlighting Genetic Pleiotropy of Kinase Gene Fusions in Soft Tissue Neoplasms

PDGFRA

USP8 fusions have recently been described in neoplasms in the provisional category of calcified chondroid mesenchymal neoplasm (CCMN). Here, we describe a cutaneous inflammatory myofibroblastic tumor (IMT) on the upper leg of a 24-year-old male harboring the same fusion product. The tumor showed a morphology typical of IMT, including a concomitant inflammatory infiltrate; in addition, there was strong immunohistochemical PDGFRα overexpression. Methylation profiling (Sarcoma classifier v12.2) was consistent with IMT (calibrated score 0.99). Herein, we review other soft tissue tumors with PDGFRA fusions, emphasizing PDGFRA::USP8 fusions, further highlighting the genetic pleiotropy of kinase gene fusions in soft tissue tumors. In addition, this case expands the landscape of kinase fusions in IMT, presented by an extremely rare cutaneous IMT.

Effective Use of ALK Inhibitors in EML4::ALK-Positive Lymphatic Malformations

Genetically targeted medications are emerging as important therapies for lymphatic malformations (LMs) unresponsive to sirolimus. We describe two patients with EML4::ALK-positive LMs, one with Gorham Stout disease and one with a large genitourinary (GU) LM, who were successfully treated with ALK inhibitors. This report adds ALK inhibitors to the growing toolbox of molecularly targeted therapies for LMs.

An ALK Immunohistochemical Pitfall: ALK-Positive Histiocytosis Versus Angiomatoid Fibrous Histiocytoma

The proliferation of recognized neoplasms related to related to rearrangements involving kinase genes, arising in diverse somatic tissue lineages, poses an increasing challenge in surgical pathology. For instance, ALK rearrangements have been observed in diverse neoplasms of epithelial, connective tissue, and hematolymphoid lineages, many of which are associated with overexpression of ALK by immunohistochemistry as a useful biomarker. An even higher order challenge and pitfall would be the scenario where a tumor without an ALK rearrangement nonetheless overexpresses the protein, thereby simulating an ALK-defined neoplasm. Herein, we present this exact scenario, where an angiomatoid fibrous histiocytoma, exhibiting the recently-described phenomenon of its overexpression of ALK, clinically, histologically, and immunophenotypically simulated ALK-positive histiocytosis.

SARCP, a Clinical Next-Generation Sequencing Assay for the Detection of Gene Fusions in Sarcomas: A Description of the First 652 Cases

An amplicon-based targeted next-generation sequencing (NGS) assay for the detection of gene fusions in sarcomas was developed, validated, and implemented. This assay can detect fusions in targeted regions of 138 genes and BCOR internal tandem duplications. This study reviews our experience with testing on the first 652 patients analyzed. Gene fusions were detected in 238 (36.5%) of 652 cases, including 83 distinct fusions in the 238 fusion-positive cases, 10 of which had not been previously described. Among the 238 fusion-positive cases, the results assisted in establishing a diagnosis for 137 (58%) cases, confirmed a suspected diagnosis in 66 (28%) cases, changed a suspected diagnosis in 25 (10%) cases, and were novel fusions with unknown clinical significance in 10 (4%) cases. Twenty-six cases had gene fusions (ALK, ROS1, NTRK1, NTRK3, and COL1A1::PDGFB) for which there are targetable therapies. BCOR internal tandem duplications were identified in 6 (1.2%) of 485 patients. Among the 138 genes in the panel, 66 were involved in one or more fusions, and 72 were not involved in any fusions. There was little overlap between the genes involved as 5'-partners (31 different genes) and 3'-partners (37 different genes). This study shows the clinical utility of a next-generation sequencing gene fusion detection assay for the diagnosis and treatment of sarcomas.

What is new in fibroblastic/myofibroblastic tumors in children

Fibroblastic and myofibroblastic neoplasms represent about 12% of pediatric soft tissue tumors. Most of these neoplasms in children are either benign or locally aggressive with rare metastasis, while malignant cases are uncommon. Diagnosing these tumors is challenging due to overlapping morphologies and the limited utility of immunohistochemistry. Advances in molecular techniques, especially RNA sequencing, have improved our understanding of the molecular drivers of these tumors, leading to better classification. Key molecular alterations, such as RTK and MAPK activation, are central in the development of tumors like infantile fibrosarcoma (IFS) and inflammatory myofibroblastic tumors (IMT). The identification of alternative fusions in IFS and IMT underscores the importance of an integrated diagnostic approach. Furthermore, new RTK-driven lesions, now included in the WHO's "NTRK-rearranged mesenchymal neoplasms", have been identified. This review provides an update on recent findings in RTK-driven myofibroblastic tumors and highlights novel entities still in need of classification.

"Update on pediatric primary liver tumors"

Liver masses are common in children, however primary malignant neoplasms are rare, representing only 1% of all pediatric cancers. Hepatocellular neoplasms are the most common primary liver malignancies and hepatoblastoma (HB) is the most frequently diagnosed. The incidence of HB, which is increasing, is approximately of 2 cases per million in the United States, followed by hepatocellular carcinoma (HCC). Pediatric primary liver tumors of mesenchymal origin are less common, except for benign vascular tumors (hemangiomas). Malignant mesenchymal neoplasms represent approximately 10-15% of all, the most common being embryonal sarcoma and malignant rhabdoid tumor. Malignant vascular tumors are rare, but epithelioid hemangioendothelioma (EHE) and angiosarcoma can be seen in children. The development and adoption of consensus diagnostic, therapeutic and risk-stratifying approaches for pediatric patients with malignant liver tumors has been historically challenged by their rarity and by their diverse clinical and histological appearance. On-going collaborative efforts of international consortia including the Children's Oncology Group (COG) in North America, the German Society of Paediatric Oncology and Haematology (GPOH), the Societe Internationale d' Oncologie Pediatrique Liver Tumor Study Group (SIOPEL) in Europe and the Japanese Liver Tumor group (JPLT), have made significant contributions to understanding the clinical and histopathological features, as well as the underlying biology of pediatric liver tumors, in particular HB. A new classification of pediatric liver tumors drafted at the international consensus meeting held in Los Angeles, has been incorporated in the recent WHO classification and is currently used by the PHITT (Paediatric Hepatic Malignancy International Tumour Trial) and other therapeutic protocols. This manuscript provides an overview of salient diagnostic features and updates in classification and molecular characterization for the most common pediatric primary liver neoplasms. It also includes a brief overview of other less common but relevant tumors, which should be considered in the differential diagnosis.

Pediatric skull inflammatory myofibroblastic tumor: a rare case report and literature review

Inflammatory myofibroblastic tumors (IMTs) represent rare neoplasms, particularly infrequent in the pediatric skull. We present a novel case of a newborn male with a 5 cm right temporal mass and discuss current diagnostic and treatment options for IMTs. A multidisciplinary effort to surgically remove the lesion was successful, and the patient's skull defect healed without neurological deficits. The etiology of IMTs remains elusive, with proposed associations with chromosomal mutations in the anaplastic lymphoma kinase (ALK) gene. Surgical excision remains the primary treatment for IMTs. Promising pharmacological treatments, like Crizotinib, warrant further research into understanding potential alternatives in IMT management.

An Inflammatory Myofibroblastic Tumor With a Novel ALKV1180L Mutation Leading to Acquired Resistance to Tyrosine Kinase Inhibitors

Inflammatory myofibroblastic tumor (IMT) is a rare mesenchymal neoplasm that can locally recur and potentially metastasize. Approximately 50% of IMTs harbor rearrangements in the gene encoding anaplastic lymphoma kinase (ALK), a receptor tyrosine kinase that can be therapeutically targeted with tyrosine kinase inhibitors (TKIs). With successful application of TKI in ALK-positive nonsmall cell carcinoma (NSCLC), ALK inhibitors are often first-line treatments for patients with unresectable or metastatic IMTs. Although acquired resistance to these agents may develop, resistance mechanisms are sparsely reported for IMTs. Here we report a case of a 71 year-old man with metastatic pulmonary IMT harboring a DCTN1::ALK fusion that progressed during alectinib TKI treatment. Whole exome sequencing of an enlarging metastatic lesion in right 4th rib revealed a novel p.V1180L mutation in the ALK tyrosine kinase domain as the mechanism of acquired resistance. To our knowledge, this is the first report of acquired p. V1180L mutation in IMTs treated with TKIs. In cases of ALK-positive IMTs that progress on TKI therapy, targeted sequencing for acquired ALK mutations may inform clinical decisions to adopt second-line therapeutic strategies.

Efficacy of core biopsies for diagnosing inflammatory myofibroblastic tumors in pediatric patients: case series from a single tertiary referral center

Background

Inflammatory myofibroblastic tumors (IMTs) are rare, often non-metastasizing neoplasms characterized by fibro/myofibroblastic spindle cells with varying infiltrates of plasma cells, lymphocytes, and/or eosinophils. Despite their generally indolent nature, IMTs can exhibit locally aggressive behavior and a significant tendency for local recurrence, making complete surgical resection the standard treatment approach. Accurate diagnosis can be challenging due to the overlap in imaging features with more aggressive tumors, necessitating preoperative biopsies to enable differential diagnosis and guide treatment decisions. The complexity of distinguishing IMTs from other malignancies underscores the importance of biopsy in establishing an accurate diagnosis and planning appropriate management strategies.

Case Description

This study presents the cases of four pediatric patients (three males, one female) diagnosed with IMT, involving tumors located in the lung (one case), bladder (one case), and liver (two cases). Initial minimally invasive biopsies, including a US-guided tru-cut core biopsy and a percutaneous core biopsy in one case, as well as endoscopic core biopsies in two other cases, yielded inconclusive results. These initial procedures failed to provide definitive diagnostic information, necessitating the use of more precise diagnostic techniques to achieve a definitive histological diagnosis of IMT.

Conclusions

The findings indicate that when initial biopsy results are inconclusive in cases suspected to be IMT, more precise diagnostic procedures may be necessary to secure a definitive diagnosis. This highlights the need for careful consideration of alternative biopsy methods to ensure accurate identification and effective management of IMT in pediatric patients.

ALK-rearranged, CD34-positive spindle cell neoplasms resembling dermatofibrosarcoma protuberans: a study of seven cases

AIMS

The majority of dermatofibrosarcoma protuberans (DFSP) harbour PDGFB or PDGFD rearrangements. We encountered ALK expression/rearrangement in a PDGFB/D-negative CD34-positive spindle cell neoplasm with features similar to DFSP, prompting evaluation of ALK-rearrangements in DFSP and plaque-like CD34-positive dermal fibroma (P-LDF).

METHODS AND RESULTS

We searched the archives of academic institutions for cases previously coded as DFSP and P-LDF. NGS-naïve or PDGFB-negative DFSP were screened for ALK (clone D5F3) expression by immunohistochemistry. NGS or ALK FISH was performed on ALK-positive cases. Methylome profiling studies were performed and compared with conventional DFSP. One case of "DFSP" and two "P-LDF" with ALK expression were identified from the archives, while four cases were detected prospectively. These seven cases (6F:1M; 8 months to 76 years) arose in the dermis of the arm (two), scalp, eyelid, thigh, abdomen, and shoulder and ranged from 0.4 to 4.2 cm. Tumours were composed of spindled cells and displayed a storiform growth pattern. Cytologic atypia was absent, and mitotic figures were scarce (0-2/10 HPFs, high power fields). The lesional cells were diffusely positive for CD34 and ALK and negative for S100 protein. By NGS (n = 5), ALK fusion partners included DCTN1 (2), PLEKHH2, and CLIP2 in DFSP-like cases and FLNA in P-LDF-like lesions. ALK FISH was positive in one (of two) cases previously labelled P-LDF. Methylome profiling of two (of three) ALK-rearranged DFSP-like tumours showed clustering with conventional DFSP in the UMAP dimension reduction plot. To date, no tumour has recurred (n = 2; 26, 27 months).

CONCLUSION

We describe a cohort of novel ALK-rearranged tumours with morphologic features similar to DFSP.

Urachal inflammatory myofibroblastic tumor with FN1: : ALK fusion: A case report and literature review

Urachal tumors are rare and comprise of both benign and malignant neoplasms. Epithelial origin tumors are more common than mesenchymal origin tumors. We report a case Urachal inflammatory myofibroblastic tumor (IMFT) in a 12 year old boy who presented with symptoms of lower abdominal pain and burning micturition. Upon evaluation was found to have a soft tissue mass anterior to urinary bladder wall. A laparoscopic excision of tumor was done. Histopathological and immunohistochemical examination confirmed the diagnosis of IMFT. Next generation sequencing identified FN1-ALK gene fusion.

Recurrent Inflammatory Myofibroblastic Tumor of Larynx Harboring a Novel THBS1::ALK Fusion

Inflammatory myofibroblastic tumor (IMT) is a rare soft tissue tumor primarily occurring in the abdominopelvic region of young patients, and it is characterized by spindle-shaped myofibroblasts, or fibroblasts surrounded by inflammatory infiltrate. Herein, we report a case of a 24-year-old male with a firm submucosal mass in the anterior right vocal fold diagnosed as an IMT that recurred 14 months later. The tumor demonstrated a novel THBS1::ALK fusion containing Exons 1-7 of the thrombospondin 1 (THBS1) gene fused to Exon 19 of the anaplastic lymphoma kinase (ALK) gene via next-generation sequencing with the NextSeq sequencer. The fusion of THBS1 to ALK potentially results in increased expression and constitutive activation of the ALK kinase domain. These findings not only broaden the repertoire of known ALK fusion partners implicated in tumorigenesis but also provide a novel avenue for investigating the etiology of recurrent IMT by considering this fusion event as a causal factor. To our knowledge, this is the second case of IMT of the larynx with this novel mutation reported in the literature and the first such case with a detailed description of this specific fusion and clinical recurrence.

A Case Report of Inflammatory Myofibroblastic Tumor of the Sphenoidal Sinus

Inflammatory myofibroblastic tumor (IMT) is a tumor composed of differentiated myofibroblastic spindle-shaped cells. It occurs in the soft tissues of the abdomen and lungs, and is very rare in the sphenoid sinus. The diagnosis depends on histopathology and immunohistochemistry, and is easily misdiagnosed. Although metastasis is rare, the recurrence rate is high. Surgical resection is the treatment of choice, and where complete resection is difficult, radiation therapy, hormonal therapy, or molecular targeted drug therapy can be administered. We report a rare case of IMT with a primary origin in the sphenoid sinus, which was entirely resected by nasal endoscopy and confirmed by histological examination.

Uterine Inflammatory Myofibroblastic Tumors: p16 as a Surrogate for CDKN2A Deletion and Predictor of Aggressive Behavior

Uterine inflammatory myofibroblastic tumors (IMTs) are rare mesenchymal neoplasms of uncertain malignant potential. Aside from the recently described risk stratification score, which has not been validated by other studies, and rare reports of aberrant p16 expression in malignant tumors, there are no criteria to reliably predict behavior. Herein, we evaluated the clinicopathologic features and p16 expression patterns in 30 IMTs, with genomic profiling performed in a subset (13 malignant, 3 benign). Fifteen patients had malignant IMTs, defined by extrauterine disease at diagnosis (n=5) or recurrence (n=10; median: 24 mo). Patients ranged from 8 to 65 (median: 51) years and tumors from 6 to 22 (median: 12.5) cm. In primary tumors (n=13), infiltrative borders were noted in 10, moderate/severe cytologic atypia in 9, tumor cell necrosis in 7, and lymphovascular invasion in 6, while mitoses ranged from 0 to 21 (median: 7) per 10 high-power fields. In contrast, 15 patients with benign IMTs ranged from 28 to 65 (median: 44) years, with follow-up of 18 to 114 (median: 41) months. Tumors ranged from 1.9 to 8.5 (median: 5.5) cm, 2 demonstrated infiltrative borders, and 1 had moderate cytologic atypia. No other high-risk histologic features were observed. Application of the previously described clinicopathologic risk stratification score in all primary IMTs with complete data (n=18) classified 8 as high-risk (all malignant), 8 as intermediate-risk (3 malignant, 5 benign), and 2 as low-risk (benign). p16 was aberrant in all malignant IMTs, with <1% expression noted in 10, overexpression (>90%) in 4, and subclonal loss in 1; all benign tumors had patchy staining (20% to 80%; median 50%). Molecular analysis detected CDKN2A deletions in 8 of 9 tumors with <1% p16 expression, while the other harbored a TERT promoter mutation. TERT promoter mutations were also identified in 2 of 3 IMTs with p16 overexpression. Neither of these alterations was detected in the 3 sequenced benign IMTs. Thus, we recommend performing p16 on all uterine IMTs, which, combined with the risk stratification score, is a promising and cost-effective tool for predicting CDKN2A status and outcome in these patients. It may be particularly useful for tumors with incomplete information for risk stratification (ie, morcellated tumors) and for further stratifying intermediate-risk IMTs when sequencing is unavailable.

Inflammatory myofibroblastic tumor from molecular diagnostics to current treatment

Inflammatory myofibroblastic tumor (IMT) is a rare neoplasm with intermediate malignancy characterized by a propensity for recurrence but a low metastatic rate. Diagnostic challenges arise from the diverse pathological presentation, variable symptomatology, and lack of different imaging features. However, IMT is identified by the fusion of the anaplastic lymphoma kinase (ALK) gene, which is present in approximately 70% of cases, with various fusion partners, including ran-binding protein 2 (RANBP2), which allows confirmation of the diagnosis. While surgery is the preferred approach for localized tumors, the optimal long-term treatment for advanced or metastatic disease is difficult to define. Targeted therapies are crucial for achieving sustained response to treatment within the context of genetic alteration in IMT. Crizotinib, an ALK tyrosine kinase inhibitor (TKI), was officially approved by the US Food and Drug Administration (FDA) in 2020 to treat IMT with ALK rearrangement. However, most patients face resistance and disease progression, requiring consideration of sequential treatments. Combining radiotherapy with targeted therapy appears to be beneficial in this indication. Early promising results have also been achieved with immunotherapy, indicating potential for combined therapy approaches. However, defined recommendations are still lacking. This review analyzes the available research on IMT, including genetic disorders and their impact on the course of the disease, data on the latest targeted therapy regimens and the possibility of developing immunotherapy in this indication, as well as summarizing general knowledge about prognostic and predictive factors, also in terms of resistance to systemic therapy.

Sarcoma of the Lung and Mediastinum

Primary sarcoma of the lung and mediastinum is rare. The diagnosis requires careful exclusion of sarcomatoid carcinoma, sarcomatoid mesothelioma, and metastases from extra-thoracic sites. This review summarizes the key morphologic, immunohistochemical, and molecular characteristics of sarcomas that are encountered in the lung and mediastinum. The tumor types discussed are synovial sarcoma, well-differentiated/dedifferentiated liposarcoma, myxoid pleomorphic liposarcoma, intimal sarcoma of the pulmonary artery, inflammatory myofibroblastic tumor, epithelioid hemangioendothelioma, primary pulmonary myxoid sarcoma, malignant peripheral nerve sheath tumor, Ewing sarcoma, and CIC-rearranged sarcoma. Relevant differential diagnoses are also addressed.

Podcast on Emerging Treatment Options for Pediatric Patients with ALK-Positive Anaplastic Large Cell Lymphoma and Inflammatory Myofibroblastic Tumors

Anaplastic large cell lymphoma (ALCL) and inflammatory myofibroblastic tumor (IMT) are rare cancers observed predominantly in children and young adults. ALCL accounts for 10-15% of all pediatric non-Hodgkin lymphomas and is commonly diagnosed at an advanced stage of disease. In children, 84-91% of cases of ALCL harbor an anaplastic lymphoma kinase (ALK) gene translocation. IMT is a rare mesenchymal neoplasm that also tends to occur in children and adolescents. Approximately 50-70% of IMT cases involve rearrangements in the ALK gene. A combination of chemotherapeutic drugs is typically used for children with ALK-positive ALCL, and the only known curative therapy for ALK-positive IMT is complete surgical resection. Crizotinib, a first-generation ALK inhibitor, was approved in the USA in 2021 for pediatric patients and young adults with relapsed or refractory ALK-positive ALCL; however, its safety and efficacy have not been established in older adults. In 2022, crizotinib was approved for adult and pediatric patients with unresectable, recurrent, or refractory ALK-positive IMT. This podcast provides an overview of ALK-positive ALCL and IMT. We discuss the current treatment landscape, the role of ALK tyrosine kinase inhibitors, and areas of future research.

Two cases of inflammatory myofibroblastic tumor treated with targeted drugs: A case report

INTRODUCTION

Inflammatory myofibroblastic tumor (IMT) is a rare invasive soft tissue tumor. Many IMTs are positive for anaplastic lymphoma kinase (ALK) with ALK gene fusion; other gene mutations have also been reported, which indicates a key role for genetic testing and the development of target therapy to optimize treatment strategies.

PATIENT CONCERNS

We report 2 patients who obtained clinical benefits following targeted treatment with ensartinib.

DIAGNOSIS

The first patient was diagnosed as IMT, with TFG-ROS1 fusion gene mutation. The second patient was IMT harboring the ALK-STRN fusion gene mutation.

INTERVENTIONS

We performed gene testing for these 2 patients. According to the test result, both patients received ensartinib 225 mg QD as targeted therapy for a 30-day cycle.

OUTCOMES

The first patient achieved partial remission and maintained a stable state for 14.7 months. The second patient was treated for 10 months and reached complete remission after 5 months and is currently still benefiting from treatment. Treatment-related side effects were mild in both patients.

CONCLUSION

Our cases provided some new insights and approaches for the clinical diagnosis and treatment of IMT.

Update on immunohistochemistry in bone and soft tissue tumors: Cost-effectively replacing molecular testing with immunohistochemistry

Soft tissue tumors form part of a challenging domain in diagnostic pathology owing to their comparative rarity, astonishing histologic diversity, and overlap between entities. Many of these tumors are now known to be defined by highly recurrent, or, in some instances, unique molecular alterations. Insights from gene profiling continue to elucidate the wider molecular landscape of soft tissue tumors; many of these advances have been co-opted by immunohistochemistry (IHC) for diagnostic applications. There now exists a multitude of antibodies serving as surrogate markers of recurrent gene fusions, amplifications, and point mutations, which, in certain settings, can replace the need for more resource and time-intensive cytogenetic and molecular genetic analyses. IHC presents many advantages including rapid turnaround time, cost-effectiveness, and interpretative reproducibility. A sensible application of these immunohistochemical markers complemented by a working knowledge of the molecular pathogenesis of bone and soft tissue tumors permits accurate diagnosis in the majority of cases. In this review, we will outline some of these biomarkers while emphasizing molecular correlates and highlighting interpretative challenges and pitfalls.

CD74/SLC34A2-ROS1 Fusion Variants Involving the Transmembrane Region Predict Poor Response to Crizotinib in NSCLC Independent of TP53 Mutations

INTRODUCTION

Variable partners and breakpoints have been reported in patients with ROS1-rearranged NSCLC. Here, we investigated the association of fusion partners and breakpoints with crizotinib efficacy in NSCLCs with common ROS1 fusions.

METHODS

DNA and RNA next-generation sequencing (NGS) and immunohistochemistry were performed to characterize ROS1 fusions.

RESULTS

Using DNA NGS, we identified ROS1 fusions in 210 cases, comprising 171 common (CD74/EZR/TPM3/SDC4/SLC34A2-ROS1) and 39 uncommon (variants identified in <5%) ROS1 fusion cases. DNA NGS detected variable ROS1 genomic breakpoints in common ROS1 fusions, whereas RNA NGS found ROS1 breakpoints mainly occurring in exons 32, 34 and 35, resulting in long (exon 32) and short (exon 34 or 35) ROS1 fusions. ROS1 immunohistochemistry revealed that membranous and cytoplasmic staining was predominant in long ROS1 fusions, whereas cytoplasmic staining was predominant in short ROS1 fusions (p = 0.006). For patients who received first-line crizotinib, median progression-free survival (mPFS) was lower in patients with long ROS1 fusions than those with short ROS1 fusions (8.0 versus 24.0 mo, p = 0.006). Moreover, mPFS for patients with and without TP53 mutations was 8.0 and 19.0 months, respectively (p = 0.159); mPFS for patients with and without BIM deletion polymorphism was 5.0 and 22.0 months, respectively (p = 0.003). When analyzing together with fusion partners, patients with long CD74/SLC34A2-ROS1 fusions were found to have shorter PFS than those with other ROS1, regardless of the presence or absence of TP53 mutations (p < 0.001 and p = 0.002, respectively).

CONCLUSIONS

Long CD74/SLC34A2-ROS1 fusions, which retain transmembrane regions in ROS1 and fusion partners, are associated with poor response to crizotinib independent of TP53 mutations.

Current treatment and novel insights regarding ROS1-targeted therapy in malignant tumors

BACKGROUND

The proto-oncogene ROS1 encodes an intrinsic type I membrane protein of the tyrosine kinase/insulin receptor family. ROS1 facilitates the progression of various malignancies via self-mutations or rearrangements. Studies on ROS1-directed tyrosine kinase inhibitors have been conducted, and some have been approved by the FDA for clinical use. However, the adverse effects and mechanisms of resistance associated with ROS1 inhibitors remain unknown. In addition, next-generation ROS1 inhibitors, which have the advantage of treating central nervous system metastases and alleviating endogenous drug resistance, are still in the clinical trial stage.

METHOD

In this study, we searched relevant articles reporting the mechanism and clinical application of ROS1 in recent years; systematically reviewed the biological mechanisms, diagnostic methods, and research progress on ROS1 inhibitors; and provided perspectives for the future of ROS1-targeted therapy.

RESULTS

ROS1 is most expressed in malignant tumours. Only a few ROS1 kinase inhibitors are currently approved for use in NSCLC, the efficacy of other TKIs for NSCLC and other malignancies has not been ascertained. There is no effective standard treatment for adverse events or resistance to ROS1-targeted therapy. Next-generation TKIs appear capable of overcoming resistance and delaying central nervous system metastasis, but with a greater incidence of adverse effects.

CONCLUSIONS

Further research on next-generation TKIs regarding the localization of ROS1 and its fusion partners, binding sites for targeted drugs, and coadministration with other drugs is required. The correlation between TKIs and chemotherapy or immunotherapy in clinical practice requires further study.

Abdominal inflammatory myofibroblastic tumour: Clinicopathological and molecular analysis of 20 cases, highlighting potential therapeutic targets

AIMS

Inflammatory myofibroblastic tumour (IMT) is a rare mesenchymal neoplasm of intermediate malignant potential, occurring at any age and at multiple sites. Epithelioid inflammatory myofibroblastic sarcoma (EIMS) is an aggressive subtype of IMT, typically involving the abdomen. Most IMTs harbour kinase gene fusions, especially involving ALK and ROS1, but 20-30% of IMTs show no detectable translocations. The aim of this study is to further delineate clinicopathological and molecular characteristics of abdominal IMT and discover potential new therapeutic targets.

METHODS AND RESULTS

In 20 IMTs, including four EIMS, RNA fusion analysis was performed, followed by multiplex DNA analysis if no ALK or ROS1 fusion was detected. Fourteen IMTs (70.0%) had an ALK translocation and the fusion partner was identified in 11, including a RRBP1::ALK fusion, not previously described in classical (non-EIMS) IMT. RANBP2::ALK fusion was demonstrated in all EIMS. One IMT had a ROS1 fusion. In all ALK/ROS1 translocation-negative IMTs mutations or fusions - as yet unreported in primary IMT - were found in genes related to the receptor tyrosine kinase (RTK)/PI3K/AKT pathway. Three of four patients with EIMS died of disease [mean survival 8 months (4-15 months)], whereas only one of 14 classical IMT patients succumbed to disease [mean follow-up time 52 months (2-204 months); P < 0.01].

CONCLUSION

This study shows the wide clinical spectrum of abdominal IMTs and affirms the poor prognosis of EIMS, raising discussion about its status as IMT subtype. Furthermore, the newly detected alterations of the RTK/PI3K/AKT pathway expand the molecular landscape of IMTs and provide potential therapeutic targets.

Endobronchial Inflammatory Myofibroblastic Tumour Masquerading as a Ruptured Hydatid Cyst

Inflammatory myofibroblastic tumours (IMTs) represent a rare group of neoplastic lesions characterized by a diverse clinical presentation. Endobronchial involvement is infrequently reported, and its manifestation mimicking the symptoms of a ruptured hydatid cyst adds an additional layer of complexity to the diagnostic challenge. This case report delves into an exceptional clinical scenario where an endobronchial IMT masqueraded as a ruptured hydatid cyst, initially confounding the diagnostic team. Through a detailed examination of the patient's clinical history, radiological imaging, bronchoscopy findings and subsequent histopathological analysis, we aim to contribute to the existing medical literature and shed light on the nuances encountered in accurately identifying and differentiating these two entities.

Reclassification of a spindle cell sarcoma after identification of a TFG-ROS1 fusion: A case demonstrating the clinical benefit of next-generation sequencing in sarcoma

BACKGROUND

Inflammatory myofibroblastic tumors (IMTs) are rare mesenchymal soft tissue sarcomas that often present diagnostic challenges due to their wide and varied morphology. A subset of IMTs have fusions involving ALK or ROS1. The role of next-generation sequencing (NGS) for classification of unselected sarcomas remains controversial.

METHODS AND RESULTS

We report a case of a metastatic sarcoma in a 34-year-old female originally diagnosed as an unclassified spindle cell sarcoma with myofibroblastic differentiation and later reclassified as IMT after NGS revealed a TFG-ROS1 rearrangement. Histologically, the neoplasm had spindle cell morphology with a lobulated to focally infiltrative growth pattern with scant inflammatory cell infiltrate. Immunohistochemistry demonstrated focal desmin and variable smooth muscle actin staining but was negative for SOX10, S100, and CD34. Fluorescence in situ hybridization was negative for USP6 or ALK gene rearrangements. NGS revealed a TFG-ROS1 rearrangement and the patient was treated with crizotinib with clinical benefit.

CONCLUSIONS

We discuss the role of NGS as well as its potential benefit in patients with unresectable, ALK-negative metastatic disease. Considering this case and previous literature, we support the use of NGS for patients requiring systemic treatment.

Functional Classification of Fusion Proteins in Sarcoma

Sarcomas comprise a heterogeneous group of malignant tumors of mesenchymal origin. More than 80 entities are associated with different mesenchymal lineages. Sarcomas with fibroblastic, muscle, bone, vascular, adipocytic, and other characteristics are distinguished. Nearly half of all entities contain specific chromosomal translocations that give rise to fusion proteins. These are mostly pathognomonic, and their detection by various molecular techniques supports histopathologic classification. Moreover, the fusion proteins act as oncogenic drivers, and their blockade represents a promising therapeutic approach. This review summarizes the current knowledge on fusion proteins in sarcoma. We categorize the different fusion proteins into functional classes, including kinases, epigenetic regulators, and transcription factors, and describe their mechanisms of action. Interestingly, while fusion proteins acting as transcription factors are found in all mesenchymal lineages, the others have a more restricted pattern. Most kinase-driven sarcomas belong to the fibroblastic/myofibroblastic lineage. Fusion proteins with an epigenetic function are mainly associated with sarcomas of unclear differentiation, suggesting that epigenetic dysregulation leads to a major change in cell identity. Comparison of mechanisms of action reveals recurrent functional modes, including antagonism of Polycomb activity by fusion proteins with epigenetic activity and recruitment of histone acetyltransferases by fusion transcription factors of the myogenic lineage. Finally, based on their biology, we describe potential approaches to block the activity of fusion proteins for therapeutic intervention. Overall, our work highlights differences as well as similarities in the biology of fusion proteins from different sarcomas and provides the basis for a functional classification.

A rare huge bladder inflammatory myofibroblastic tumor treated by en bloc resection with diode laser: a case report and literature review

Background

Inflammatory myofibroblastic tumor (IMT) is a rare neoplasm with malignant potential. Bladder IMT is even rarer and mainly treated by surgical resection However, partial or radical cystectomy would affect the quality of life of patients due to major surgical trauma, and classical TURBT is hard to avoid intraoperative complications including obturator nerve reflex and bleeding etc. Therefore, the safe and effective better choice of surgical approaches become critical to bladder IMT.

Case presentation

A 42-year-old male patient was admitted to the department of urology with persistent painless gross hematuria for more than 10 days without the presentation of hypertension. Preoperative routine urine examination of red blood cells was 7738.9/HPF (normal range ≤ 3/HPF). CTU indicated a space occupying lesion (6.0 cm×5.0 cm) in the left posterior wall of the bladder with heterogeneous enhancement in the excretory phase. MRI also indicated bladder tumor with slightly equal SI on T1WI and mixed high SI on T2WI (6.0 cm×5.1cm×3.5cm) in the left posterior wall of the bladder. En bloc resection of bladder IMT with 1470 nm diode laser in combination of removing the enucleated tumor by the morcellator system was performed. Postoperative pathological examination revealed bladder IMT, with IHC positive for Ki-67 (15-20%), CK AE1/AE3, SMA, and Desmin of bladder IMT and negative for ALK of bladder IMT as well as FISH negative for ALK gene rearrangement. Second TUR with 1470 nm diode laser was performed within 6 weeks to reduce postoperative risk of recurrence due to highly malignant potential for the high expression of Ki-67 (15-20%) and negative ALK in IHC staining. The second postoperative pathology report showed chronic inflammation concomitant with edema of the bladder mucosa without bladder IMT, furthermore no tumor was observed in muscularis propria layer of bladder. No recurrence occurred during the period of 24-month follow-up.

Conclusion

En bloc resection of bladder IMT in combination of the following second transurethral resection with 1470 nm diode laser is a safe and effective surgical approach for the huge bladder IMT with highly malignant potential.

Mimickers of immunoglobulin G4-related hepatobiliary disease on biopsy

With the growing recognition of IgG4-related hepatobiliary disease, establishing a definitive diagnosis relies mainly on a combination of clinical findings, serological markers, and imaging modalities. However, the role of histopathological evaluation remains indispensable, particularly in cases necessitating differential diagnosis or malignancy exclusion. While diagnosing IgG4-related hepatobiliary disease through surgical resection specimens is often straightforward, pathologists encounter substantial challenges when evaluating biopsies. The increasing rarity of surgical interventions exacerbates this due to improved disease recognition and suspicion. Numerous confounding factors, including the absence of the characteristic histologic features, limited tissue sample size, biopsy artifacts, and the limited value of IgG4 counts, further complicate the diagnostic process. Additionally, many other disorders exhibit clinical and histological features that overlap with IgG4-related disease, intensifying the complexity of interpreting biopsy specimens. This article explores the clinical and histomorphologic features of IgG4-related hepatobiliary disease and its potential mimickers. It offers valuable insights for pathologists and clinicians when confronted with biopsy specimens from hepatobiliary organs.

A rare inflammatory myofibroblastic tumor appearing both inside and outside the heart

BACKGROUND

Inflammatory myofibroblastic tumor (IMT) is an uncommon cardiac tumor that primarily affects infants, children, and young adults. While complete surgical resection generally leads to a favorable prognosis, accurate diagnostic tests remain limited.

CASE PRESENTATION

We describe the case of a 26-year-old female who had a dual tumor inside and outside the heart and was misdiagnosed by echocardiography and MRI. We also review 71 cases of cardiac IMTs from the literature regarding their epidemiology, clinical presentation, and outcome.

CONCLUSION

Early detection of this rare disorder is essential for optimal surgical management.

Kinase Fusions in Spitz Melanocytic Tumors: The Past, the Present, and the Future

In recent years, particular interest has developed in molecular biology applied to the field of dermatopathology, with a focus on nevi of the Spitz spectrum. From 2014 onwards, an increasing number of papers have been published to classify, stratify, and correctly frame molecular alterations, including kinase fusions. In this paper, we try to synthesize the knowledge gained in this area so far. In December 2023, we searched Medline and Scopus for case reports and case series, narrative and systematic reviews, meta-analyses, observational studies-either longitudinal or historical, case series, and case reports published in English in the last 15 years using the keywords spitzoid neoplasms, kinase fusions, ALK, ROS1, NTRK (1-2-3), MET, RET, MAP3K8, and RAF1. ALK-rearranged Spitz tumors and ROS-1-rearranged tumors are among the most studied and characterized entities in the literature, in an attempt (although not always successful) to correlate histopathological features with the probable molecular driver alteration. NTRK-, RET-, and MET-rearranged Spitz tumors present another studied and characterized entity, with several rearrangements described but as of yet incomplete information about their prognostic significance. Furthermore, although rarer, rearrangements of serine-threonine kinases such as BRAF, RAF1, and MAP3K8 have also been described, but more cases with more detailed information about possible histopathological alterations, mechanisms of etiopathogenesis, and also prognosis are needed. The knowledge of molecular drivers is of great interest in the field of melanocytic diagnostics, and it is important to consider that in addition to immunohistochemistry, molecular techniques such as FISH, PCR, and/or NGS are essential to confirm and classify the different patterns of mutation. Future studies with large case series and molecular sequencing techniques are needed to allow for a more complete and comprehensive understanding of the role of fusion kinases in the spitzoid tumor family.

A case of inflammatory myofibroblastic tumor harboring EML4-ALK fusion with a brain metastasis responding to alectinib

Metastatic inflammatory myofibroblastic tumor (IMT) is very rare and detailed reports on diagnosis and treatment are limited. Here, we report a case of metastatic IMT with ALK rearrangement. A 73-year-old woman was diagnosed with IMT involving a brain metastasis. Next generation sequencing (NGS) panel testing with Oncomine dx target test revealed that her tumor was positive for EML4-ALK. Treatment with alectinib was initiated, resulting in remarkable shrinkage of both the primary tumor and the brain metastasis. This report is the first to identify ALK rearrangement in IMT using a commercially available NGS panel testing, followed by treatment with alectinib. This case suggests that NGS panel testing may be useful in the diagnosis and treatment of patients with metastatic IMT.

Unraveling the spectrum of inflammatory myofibroblastic tumors in the lung: A comprehensive case series highlighting endobronchial, pleural, and lung parenchymal tumors

Objectives

Diverse cases of inflammatory myofibroblastic tumors (IMTs) in the lung (pleural, endobronchial, and parenchymal) are presented while discussing the (preoperative) diagnostic challenges and treatment modalities. Other objectives include emphasizing the significance of gene rearrangements and highlighting the multidisciplinary approach in addressing IMTs.

Methods

Four cases of IMT in the lung are presented, including a young adolescent girl with an ETV6-neurotrophic tyrosine receptor kinase 3 (NTRK3) gene rearrangement, a 5-year-old boy with challenging preoperative diagnosis, and 2 middle-aged women with respectively pleural and endobronchial tumors with one peribronchial relapse.

Results

The cases demonstrate the diverse clinical presentations and diagnostic complexities associated with IMT in the lung. Surgical resection remains the primary treatment modality, with complete resection leading to a cure in most patients. Unfortunately, aggressive relapse can occur, as in our last case of an endobronchial tumor. Frozen section may confirm the presence of malignant cells perioperatively and impact further treatment. The presence of gene rearrangements, such as ETV6-NTRK3, suggests potential therapeutic implications.

Conclusions

Early detection and complete surgical removal of IMT are crucial for effective treatment. Identifying gene rearrangements such as ETV6-NTRK3 holds promise for targeted therapies. Diagnostic challenges, including the controversy of biopsies and preoperative evaluations, underscore the importance of a multidisciplinary approach. Anatomopathological recognition of IMT stays demanding. Close surveillance is necessary due to potential relapse, whereas frozen section perioperatively can help further treatment. This case series emphasizes the diagnostic challenges and therapeutic considerations for IMT in the lung.

Case report: Adult NTRK-rearranged spindle cell neoplasms with TPM3-NTRK1 fusion in the pelvic

NTRK-rearranged spindle cell neoplasms (NTRK-RSCNs) are rare soft tissue tumor molecularly characterized by NTRK gene rearrangement, which occurs mostly in children and young adults, and rarely in adults. The abnormal tumor located in superficial or deep soft tissues of human extremities and trunk mostly, and rarely also involves abdominal organs. In this case, we report a malignant NTRK-RSCN that occurred in the pelvic region of an adult. The patient was found to have a large tumor in the pelvic region with a pathological diagnosis of infiltrative growth of short spindle-shaped tumor cells with marked heterogeneity. Immunohistochemistry of this patient showed positive vimentin, pan-TRK and Ki67 (approximately 60%) indicators with negative S100, Desmin and DOG1. Molecular diagnosis revealed c-KIT and PDGFRα wild type with TPM3-NTRK1 fusion, unfortunately this patient had a rapidly progressive disease and passed away. This case highlights the gene mutation in the molecular characteristics of NTRK-RSCNs, and the significance of accurate molecular typing for the diagnosis of difficult cases.

Gastric and cardiac inflammatory myofibroblastic tumor: an extremely rare case

BACKGROUND

Inflammatory myofibroblastic tumor (IMT) is a unique, rarely metastatic tumor composed of myofibroblasts and fibrous spindle cells with inflammatory cell infiltration that can affect any organ in the human body. By reviewing the relevant literature on PubMed, we found that this is the first case report of IMT with both gastric and cardiac involvement.

CASE PRESENTATION

A 57-year-old male patient was admitted to the hospital with complaints of malaise, poor appetite, and epigastric pain with black stools. We found a mass in the patient's stomach and left atrium by contrast-enhanced computed tomography, 18 F-fluorodeoxyglucose positron emission tomography/computed tomography, and other tests. The patient underwent laparoscopic Billroth II subtotal gastrectomy and Braun's gastrointestinal reconstruction under general anesthesia. On the 46th day following stomach surgery, the cardiac tumor was removed under general anesthesia. The patient has treated with doxorubicin 70 mg of D1 chemotherapy two months after cardiac surgery. Postoperative pathological immunohistochemistry of the mass confirmed the diagnosis of an IMT. His review three months after the cardiac surgery suggested the progression of the left atrial mass, but he declined further treatment and finally died one month after the review.

CONCLUSIONS

As a unique class of tumors that rarely metastasize, IMTs have an unknown etiology and pathogenesis, and distant metastasis is primarily observed in patients with negative activin receptor-like kinase (ALK) expression. The preferred treatment for IMT is complete surgical resection, and the effectiveness of adjuvant therapy for patients with distant metastases is still being determined. The clinical presentation of IMT lacks specificity and is often related to the location of tumor growth, which poses a diagnostic challenge. Pathological immunohistochemistry is the only way to confirm the diagnosis at present. Our case report reminds clinicians that a category of ALK-negative IMT with a tendency toward distant metastasis should not be ignored.

Practical Considerations for Oncogenic Fusion Detection and Reporting in Solid Tumors

BACKGROUND

Chromosomal rearrangements that result in oncogenic fusions can hold tremendous clinical significance in solid tumors, often with diagnostic or treatment implications.

CONTENT

Traditionally, low-throughput methods such as fluorescence in situ hybridization were used to identify fusions in the clinical laboratory. With the rise of next-generation sequencing techniques and the broad adoption of comprehensive genomic profiling, the practice of screening for fusions as part of an oncologic workup has evolved. RNA sequencing methods are increasingly used, as these comprehensive high-throughput assays have many advantages over traditional techniques. Several RNA sequencing platforms are available, each with benefits and drawbacks. Regardless of the approach, systematic evaluation of the RNA sequencing results and the fusions identified by the assay should be performed. Assessment of fusion events relies upon evaluation of quality evidence, structural evidence, and functional evidence to ensure accurate fusion reporting and interpretation.

SUMMARY

Given the clinical significance of gene fusions in oncology, understanding the variety of assays available for fusion detection, their benefits and drawbacks, and how they are used in the identification and interpretation of gene fusions is important for the modern precision oncology practice.

New Perspectives in the Treatment of Inflammatory Myofibroblastic Tumor with ALK Translocation: Case Report

Introduction

Inflammatory myofibroblastic tumor (IMT) is a rare entity, classified within soft tissue sarcomas. It is an intermediate malignancy tumor, which seldom presents as metastatic disease. The treatment of choice is surgery, except in cases where surgery is not possible due to localization or if it presents with metastatic disease. Approximately 50% of IMTs will exhibit ALK translocation, providing a therapeutic target for these patients.

Case Presentation

A case is presented of a patient with metastatic IMT in complete response to treatment with alectinib, maintained for over 4 years.

Conclusion

This case showed a long time complete response in patient with IMT treated with alectinib.

Mesenchymal tumours of the pleura: review and update

Primary mesenchymal tumours of the pleura are uncommon and can be diagnostically challenging due to their overlapping histopathologic and immunophenotypic features. Herein we discuss selected mesenchymal tumours of the pleura, including solitary fibrous tumour, calcifying fibrous tumour, desmoid fibromatosis, synovial sarcoma, schwannoma, malignant peripheral nerve sheath tumour, inflammatory myofibroblastic tumour, follicular dendritic cell sarcoma, epithelioid hemangioendothelioma, and desmoplastic small round cell tumour. We review their clinicopathologic characteristics, along with an update on the relevant immunohistochemical and molecular features.

Individualized targeted treatment in a case of a rare TFG::ROS1 fusion positive inflammatory myofibroblastic tumor (IMT)

BACKGROUND

Inflammatory myofibroblastic tumor (IMTs) are rare mesenchymal neoplasms with slow growth. Resection is considered as therapeutic standard, with chemotherapy being insufficiently effective in advanced disease. ALK translocations are present in 50% of cases, ROS1 fusions (YWHAE::ROS1, TFG::ROS1) are extremely rare. Here, we present a case with TFG::ROS1 fusion and highlight the significance of molecular tumor boards (MTBs) in clinical precision oncology for post-last-line therapy.

CASE PRESENTATION

A 32-year-old woman presented with IMT diagnosed at age 27 for biopsy and treatment evaluation. Previous treatments included multiple resections and systemic therapy with vinblastine, cyclophosphamide, and methotrexate. A computed tomography scan showed extensive tumor infiltration of the psoas muscles and the posterior abdomen. Next generation sequencing revealed an actionable ROS1 fusion (TFG::ROS1) with breakpoints at exon 4/35 including the kinase domain and activating the RAS-pathway. TFG, the Trk-fused gene, exerts functions such as intracellular trafficking and exhibits high sequence homology between species. Based on single reports about efficacy of ROS1-targeting in ROS1 translocation positive IMTs the patient was started on crizotinib, an ATP-competitive small molecule c-MET, ALK and ROS1-inhibitor. With a follow-up of more than 9 months, the patient continues to show a profound response with major tumor regression, improved quality of life and no evidence for severe adverse events.

CONCLUSION

This case underscores the importance of the availability of modern molecular diagnostics and interdisciplinarity in precision oncology to identify rare, disease-defining genotypes that make an otherwise difficult-to-treat disease targetable.