Pediatric Bladder Inflammatory Myofibroblastic Tumor: A Rare Case Report and Treatment Approach

Inflammatory myofibroblastic tumor (IMT) is a rare mesenchymal neoplasm with intermediate malignancy potential, commonly affecting the lungs and intra-abdominal organs but rarely the bladder. We report a 10-year-old girl with bladder IMT presenting as painless hematuria leading to syncope and requiring transfusion. Initial biopsy suggested rhabdomyosarcoma, but histopathology confirmed IMT. Partial bladder resection was performed, followed by crizotinib treatment due to positive margins and recurrent symptoms. One-year follow-up showed no recurrence. This case highlights the importance of early diagnosis, surgical management, and targeted therapy. Further studies are needed to optimize treatment strategies for pediatric bladder IMT.

Inflammatory myofibroblastic tumor (IMT) is a rare mesenchymal neoplasm with intermediate malignancy potential, primarily affecting children and young adults [1]. Its diverse histological and radiological features, variable behavior including spontaneous regression, local recurrence, and metastasis and rarity contribute to its incomplete understanding [2]. It can arise in various locations, most commonly in the lung, retroperitoneum, and gastrointestinal tract [3]. Only 9.5% of extrapulmonary IMTs originate from the genitourinary system, with the bladder being the most common site in the genitourinary tract [4]. Symptoms depend on tumor size and location. It is estimated that one-third of patients exhibiting systemic symptoms such as fever, fatigue, growth retardation, or anemia [5, 6]. Complete resection is the preferred treatment, but systemic therapies are considered for unresectable or incompletely removed tumors. Advances in tumor biology and genetics have facilitated targeted therapies, yet optimal management remains uncertain. Bladder masses are rare in pediatric patients, complicating diagnosis and necessitating histological confirmation. We report a case of a 10-year-old girl with macroscopic hematuria due to a bladder IMT. Case Report A 10-year-old female was admitted to another hospital with painless gross macroscopic hematuria leading to syncope and requiring transfusion. Ultrasonography (US) revealed a well-circumscribed mass lesion located at the bladder base. Due to uncontrollable hematuria, a palliative laparotomy was performed. Initial biopsy suggested rhabdomyosarcoma, but histopathological evaluation confirmed an inflammatory myofibroblastic tumor (IMT). The patient was subsequently referred to our institution for further examination and management. The patient’s medical history was otherwise unremarkable, and both physical examination and hematologic evaluations were normal. Abdominal US demonstrated a well-defined hypoechoic lesion measuring 30×20 mm at the base of the bladder, with no calcification. Color Doppler imaging indicated mild vascularization of the lesion. Magnetic resonance imaging (MRI) revealed a contrast-enhanced solid mass measuring 20×23×30 mm located in the left posterolateral wall of the bladder, near the bladder neck (Fig. 1). On the cystoscopy, the right ureter orifice was seen, but the left orifice was not discernible due to the protruding mass on the left side of the bladder, which extended to the bladder neck. The patient underwent partial bladder resection, preserving both the ureters and the trigone. Since the diagnosis was previously confirmed by biopsy, excision was performed with the aim of preserving bladder function and the left ureter. Postoperative recovery was uneventful, with no complications. The diagnosis of inflammatory myofibroblastic tumor was confirmed by histopathological examination. The surgical margins were positive. Immunohistochemical analysis revealed patchy staining with smooth muscle actin, focal weak positivity with ALK, and negativity with desmin. Staining for Myo D1 and myogenin was nonspecific. The Ki-67 proliferation index was approximately 5% (Fig. 2). Our patient was followed for six months without treatment. Later, the complaint of hematuria recurred, and hence MRI was performed. Minimal nonspecific wall thickening was observed in the bladder. No findings in favor of recurrence were found. The patient was started on crizotinib treatment due to recurring complaints and positive surgical margins. She has been using crizotinib for ten months. Hematuria resolved with crizotinib treatment and after one year follow-up there are no evidence of recurrent disease.

Inflammatory myofibroblastic tumors (IMT) are rare mesenchymal neoplasms, primarily affecting the lungs and intra-abdominal organs but occasionally arising in genitourinary structures like the bladder [6]. In pediatric patients, bladder IMTs are exceptionally rare, necessitating a multidisciplinary diagnostic and treatment approach. Their unpredictable clinical behavior, from benign to locally aggressive forms, highlights the comprehensive management strategies. The clinical presentation of IMT varies by tumor localization. In bladder IMTs, common symptoms include hematuria, dysuria, and obstructive urinary symptoms [7]. These symptoms can mimic other benign and malignant bladder lesions, making imaging and histopathological confirmation essential. In our case, the patient presented with painless gross hematuria leading to syncope and requiring transfusion, a rare and severe manifestation of bladder IMT. Definitive diagnosis is established through histopathological examination and immunohistochemical analysis. The hallmark histological features of IMT include spindle cell proliferation with an inflammatory infiltrate rich in plasma cells, lymphocytes, and eosinophils [8]. Immunohistochemical staining for anaplastic lymphoma kinase (ALK), smooth muscle actin (SMA), and desmin aids in distinguishing IMTs from other spindle cell neoplasms. Our case exhibited patchy SMA positivity, focal weak ALK positivity, and negativity for desmin, with a Ki-67 proliferation index of approximately 5%, consistent with previously reported findings in bladder IMTs [8, 9]. The etiology of IMT is still unclear. There are hypotheses that infection, trauma, instrumentation and immunosuppression are effective in pathogenesis [10, 11]. Genetic abnormalities also play a key role in tumorigenesis, as ALK gene mutations are identified in 50–70% of cases [12]. In pediatric bladder IMTs, ALK positivity serves as a crucial biomarker for treatment decisions, while ALK-negative tumors tend to be more aggressive, necessitating alternative therapies [13]. Other genetic alterations, including ROS1 and PDGFRB rearrangements, have been implicated in a subset of IMTs, suggesting potential targets for novel therapies [14]. Surgical intervention is the primary treatment option for patients with localized inflammatory myofibroblastic tumors [15]. Although this tumor is generally considered benign, some cases have been reported to exhibit distant metastasis or local recurrence. The incidence of local recurrence in large pediatric series has been reported to range from 15% to 37% [16]. However, as illustrated by the case we presented, partial excision may also be considered in cases where organ involvement could impact vitality, quality of life, and functionality. In cases where surgical margins are not clear or when complete resection is challenging, additional therapeutic options are considered. ALK inhibitors such as crizotinib and alectinib have demonstrated promising outcomes in ALK-positive IMTs, providing an effective non-surgical alternative [17, 18]. Our patient initially underwent surveillance after surgery but later developed recurrent hematuria, prompting an MRI evaluation, which showed minimal nonspecific bladder wall thickening without evidence of recurrence. Due to her persistent symptoms and positive margins, she was started on crizotinib treatment, which led to complete resolution of hematuria and no signs of disease recurrence at one-year follow-up. This aligns with previous reports demonstrating crizotinib’s efficacy in achieving remission in ALK-positive IMTs [18]. While IMTs generally have a favorable prognosis, recurrence rates vary depending on tumor localization, histological features, and completeness of resection. A study on recurrent IMTs reported that bladder IMTs may recur following transurethral resection, particularly in cases with positive surgical margins or incomplete excision, emphasizing the need for long-term follow-up [19]. Close post-treatment monitoring with periodic imaging is recommended to detect early recurrence and guide further management. The integration of molecular profiling into treatment planning enables a more personalized approach, optimizing therapeutic outcomes for pediatric patients with IMTs.

Pediatric bladder IMTs are rare and require detailed clinical and pathological evaluation for optimal treatment. ALK mutations play a key role in therapeutic decisions, supporting the use of targeted therapies alongside surgery. Total excision is preferred when feasible; otherwise, organ- and function-preserving surgery should be considered. Our case highlights the importance of early diagnosis, surgical management, and targeted therapy for residual disease, demonstrating crizotinib’s efficacy in preventing recurrence. Advances in molecular diagnostics and targeted therapies offer promising prospects, particularly for recurrent or unresectable cases. Larger studies are needed to further clarify the pathogenesis, genetic profile, and optimal treatment strategies for pediatric IMTs. Conflicts of Interest There are no conflicts of interest. Financial Support and Sponsorship Nil.

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Authors Metrics & Citations Metrics Article Usage 251views 163downloads Citations Download citation Kubra Ozturk Yuzdemir, Idil Rana User, H.Nursun Ozcan, et al. Pediatric Bladder Inflammatory Myofibroblastic Tumor: A Rare Case Report and Treatment Approach. Authorea. 18 March 2025. DOI: https://doi.org/10.22541/au.174228171.18055562/v1 DOI: https://doi.org/10.22541/au.174228171.18055562/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu.