Diagnostic challenges and clinical management of inflammatory myofibroblastic tumor: a retrospective case series study

Introduction

Inflammatory myofibroblastic tumor (IMT) is a rare mesenchymal tumor that originates from muscle and connective tissue. Its biological behavior lies between reactive hyperplasia and low-grade malignant soft tissue sarcoma (1). Although most IMTs present with an inert course and can be cured after local resection. Moreover, some cases (especially those in specific sites or with specific gene fusions) may exhibit aggressive behaviors, including local recurrence, distant metastasis, and even malignant transformation (2). IMT can occur at any age, typically in adolescents and children, with a male-to-female ratio of approximately 2:1 (3). The etiology of IMT remains unclear, but it may be related to factors such as inflammatory responses and gene mutations (4). Clinically, common symptoms of IMT include local masses, pain, sometimes accompanied by fever and general discomfort. IMT (5) mostly occurs in the chest, abdomen, and pelvis, but it can also occur in other sites. The existing clinical guidelines are mostly based on the limited data of IMT in the lungs or abdominal cavity. There is no consensus on the diagnostic criteria, risk assessment, and treatment strategies for IMT in rare sites. In imaging examinations (6,7), IMT presents as round, oval, or irregular masses. Most of them have clear boundaries and uneven low-density or high-density areas inside. Although modern imaging techniques [such as multimodal magnetic resonance imaging (MRI) and positron emission tomography (PET)-computed tomography (CT)] can improve the detection rate of lesions, it is still difficult to accurately distinguish IMT from other invasive tumors. The diagnosis of IMT relies on tissue biopsy and immunohistochemical staining. Although molecular tests [such as anaplastic lymphoma kinase (ALK) rearrangement] have been gradually applied in diagnosis, their value in predicting the biological behavior of IMT in different anatomical sites remains to be clarified. In terms of treatment, surgical resection (8) is the preferred method. For cases where surgical resection is not feasible or recurrence occurs, combined treatment methods such as radiotherapy and chemotherapy (4) can be considered. The prognosis of IMT patients varies from person to person. Generally speaking, benign IMT has a relatively better prognosis, while malignant IMT has a poorer prognosis. Due to the rarity and diverse clinical manifestations of IMT, in-depth research on IMT is conducive to improving the accuracy of diagnosis and treatment, thereby enhancing the prognosis of patients.

This study systematically analyzed six cases of IMT occurring in atypical sites such as the nasal cavity, sacrum, and bladder, aiming to reveal the special diagnostic dilemmas and treatment challenges faced by such tumors in clinical practice. The common theme of these cases is that even if the pathological manifestation is “low grade”, IMT occurring in specific anatomical sites can still present an unexpected invasive course (such as early recurrence or distant metastasis). This observation provides an important supplement to the current clinical paradigm that relies on pathological grading for prognosis assessment. By combining case data with literature comparison, we aim to provide a basis for improving individualized diagnosis and treatment strategies for this type of disease. We present this article in accordance with the AME Case Series reporting checklist (available at https://tcr.amegroups.com/article/view/10.21037/tcr-2025-1-2571/rc).

Case presentation

Materials and methods

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patients or legal guardians for the publication of this case series and accompanying images. A copy of the written consent is available for review by the editorial office of this journal. Between 2021 and 2022, six patients with IMT received surgical treatment at The Affiliated Hospital of Guizhou Medical University. We retrospectively collected the clinical data, imaging features, treatment measures, pathological diagnoses, and follow-up data of these patients. All the patients underwent CT or MRI. All the pathological sections were analyzed by experienced pathologists. Follow-up was usually conducted every 3 months in the first year, and every 6 months thereafter.

Clinical information

Table 1 summarizes the basic demographic characteristics and clinical manifestations of the six IMT patients. The patients had an average age of 41.67 years (range, 15 to 63 years). Of the six patients, three were female and three were male. The tumor was located in the right nasal cavity in one patient, the left upper arm in one patient, the right anterior chest wall in one patient, the sacrum in one patient, and the bladder in two patients. Two patients presented with a mass, two with pain, one with bleeding, and one with pain with hematuria. The maximum tumor diameter ranged from 2.0 to 9.5 cm (mean: 4.4 cm). No obvious abnormalities were found in the inflammation-related indicators and special tumor markers of all patients. Preoperative imaging showed no obvious lymph node enlargement, and the tumor growth rate was slow. At the time of diagnosis, immunoglobulin G4 (IGG4)-related diseases, lymphoma, sarcoma, and other diseases are not inclined to be considered.

Imaging features

Figure 1 shows the imaging findings of five patients with IMT. The patient with the sacral IMT had incomplete imaging data and was not included. In all three cases, the largest tumor was 9.5 cm in diameter. The tumors were oval or irregular in shape. The tumor boundaries were clear in 3 cases (60%) and blurred in 2 cases (40%). Four patients underwent enhanced CT, and all of these cases (100%) showed uneven enhancement. No invasion of adjacent tissues or distant metastasis was observed in these five patients. A tumor was observed in the preoperative imaging of each of the 5 patients (100%).

Figure 1 Imaging pictures. (A) CT of right nasal cavity tumor. (B) Enhanced CT of right nasal cavity tumor. (C) CT of recurrent tumor in the right nasal cavity. (D) MRI T1-weighted image of left upper arm tumor. (E) MRI T2-weighted image of left upper arm tumor. (F) Enhanced CT of right chest wall tumor. (G) CT of right bladder wall tumor. (H) Enhanced CT of right bladder wall tumor. (I) CT of right bladder wall tumor. (J) Enhanced CT scan of right bladder wall tumor. CT, computed tomography; MRI, magnetic resonance imaging.

Management

Case 1: a patient with right nasal IMT underwent nasal tumor resection at an external hospital 3 years ago. Postoperative pathology indicated IMT, and no further treatment was administered. The patient was admitted 2 months ago due to symptom recurrence, and further examinations confirmed tumor recurrence. After admission, endoscopic nasal tumor resection was performed. Intraoperatively, the tumor was found to be large with multiple areas of invasion, making complete resection impossible; therefore, palliative tumor resection was performed. Postoperatively, the patient received regular radiotherapy and chemotherapy. Symptoms recurred 7 months later, leading to another palliative surgical procedure, followed by continued adjuvant radiotherapy and chemotherapy. The patient died 4 months after the second surgery. The overall survival time from initial tumor detection to death was 4 years. Case 2: a patient with left upper arm IMT discovered a mass in the left upper arm measuring approximately 0.8 cm × 0.8 cm 3 years ago and underwent mass resection at an external hospital. Intraoperative margin assessment was not performed. Postoperative pathology indicated IMT, and no further treatment was administered. The mass recurred 1 month after surgery and gradually increased in size, reaching approximately 3 cm × 6 cm upon admission. After admission, surgical treatment was performed. Intraoperatively, the tumor tissue was found to be densely adherent to surrounding structures; therefore, a portion of normal muscle tissue along with the tumor was completely resected. Postoperative adjuvant radiotherapy was administered. Case 3: a patient with right anterior chest wall IMT presented with a right chest wall mass for 6 months. A biopsy at an external hospital suggested pleomorphic undifferentiated sarcoma. After admission, surgical treatment was performed. Intraoperatively, the tumor was clearly demarcated from surrounding tissues, with intact rib periosteum, and was completely resected. Intraoperative irrigation with lobaplatin was performed, followed by postoperative adjuvant radiotherapy. Case 4: a patient with right sacral IMT presented with right hip pain. Examinations at an external hospital 1 month earlier revealed PET-CT findings suggestive of multiple bone-destructive lesions, raising suspicion of systemic multiple bone metastases. Subsequently, a biopsy of the sacral mass confirmed myofibroblastoma. Open surgery was performed to expose the tumor, ligate the vessels supplying the tumor tissue, and carry out ablation for inactivation. After tumor inactivation, the tumor within the muscle tissue was excised using an electrocautery knife, and the tumor tissue within the sacral bone was thoroughly curetted. Bone cement reconstruction was performed. Postoperatively, the patient received radiotherapy, chemotherapy, and oral medications for symptomatic pain relief. Case 5: a patient with right lateral wall bladder IMT was admitted due to painful urination lasting 1 month. Cystoscopy at an external hospital suggested multiple bladder-occupying lesions. A biopsy indicated urothelial papilloma. After admission, transurethral resection of the bladder tumor (TURBT) was performed, with resection reaching the muscle layer. Postoperative biopsy revealed a papillary urothelial tumor combined with myofibroblastoma. Postoperative intravesical chemotherapy was administered. Case 6: a patient with right lateral wall bladder IMT was admitted due to painful urination and hematuria lasting 1 month. Ultrasound examination confirmed a bladder-occupying lesion. After admission, TURBT was performed, with resection reaching the muscle layer. Postoperative biopsy indicated myofibroblastoma. No specific treatment was administered postoperatively.

Histopathology

The pathological features of the IMT patients are shown in Figure 2. The gross tumor specimens were mostly oval solid masses, and the sections were mostly composed of grayish-white or grayish-brown tissue. Microscopic examinations showed that the tumors were formed by fusiform muscle fibers and inflammatory cells. Spindle cells were detected by immunohistochemistry in the six patients, and no necrotic changes were observed in any of the patients. Immunohistochemical staining showed that vimentin (6/6, 100%) and smooth muscle actin (SMA) (6/6, 100%) were expressed in the tumor cells of the six patients, while desmin was expressed in the tumor cells of four patients (4/6, 66.67%). The expression of ALK was tested by immunohistochemistry in only two patients, both of whom tested positive (2/2, 100%), but the results were not evaluated further, as the other patients were not tested for ALK.

Figure 2 Pathological features of IMT (×100). HE staining of right nasal cavity tumor (A), left upper arm tumor (B), right chest wall tumor (C), right sacral tumor (D), and right bladder tumor (E) showing that the tumors were composed of fusiform muscle fibroblasts. Immunohistochemistry of bladder tumors showing vimentin positive (F), SMA positive (G), desmin positive (H), and Ki-67 positive (I). HE, hematoxylin and eosin; IMT, inflammatory myofibroblastic tumor; SMA, smooth muscle actin.

Follow-up

All the IMT patients underwent surgery to remove the tumor and were actively followed up after surgery. Follow-up was conducted every 3 months in the first year and every 6 months thereafter. The average follow-up time was 19.67 months (range, 13–33 months). Case 1: a patient with right nasal IMT underwent surgical treatment at an external hospital 3 years ago due to nasal bleeding. The patient’s symptoms improved after the procedure. Three years later, symptoms recurred, and the patient underwent surgical treatment at The Affiliated Hospital of Guizhou Medical University. Postoperative symptoms gradually improved, and the patient received radiotherapy and chemotherapy. Symptoms recurred 7 months later, prompting another surgical intervention, followed by continued radiotherapy and chemotherapy. The patient died 4 months after the second surgery. Case 2: a patient with left upper arm IMT discovered a mass in the left upper arm 3 years ago and underwent mass resection at an external hospital. No special treatment was administered postoperatively. The mass recurred 1 month after surgery and gradually increased in size. Three years later, the patient underwent surgical treatment at The Affiliated Hospital of Guizhou Medical University, followed by regular radiotherapy. To date, no significant recurrence or metastasis has been observed during follow-up. Case 3: a patient with right anterior chest wall IMT underwent surgical treatment at The Affiliated Hospital of Guizhou Medical University, followed by regular radiotherapy. To date, no significant recurrence or metastasis has been observed during follow-up. Case 4: a patient with right sacral IMT was diagnosed with suspected systemic multiple bone metastases at the time of diagnosis. Surgical resection of the sacral tumor was performed, resulting in improvement of right hip pain. Postoperative radiotherapy and chemotherapy were administered irregularly. To date, follow-up examinations have shown no significant recurrence in the sacral region and no evidence of extraosseous metastasis. The patient reported multiple bone pain, which was managed with symptomatic pain relief medication. Case 5: a patient with right lateral wall bladder IMT underwent surgical treatment after admission, leading to improvement in urination. Postoperative intravesical chemotherapy was administered. To date, no significant recurrence or metastasis has been observed during follow-up, and no obvious urinary abnormalities have been reported. Case 6: a patient with right lateral wall bladder IMT underwent surgical treatment after admission, resulting in improved urination. No special treatment was administered postoperatively. To date, no significant recurrence or metastasis has been observed during follow-up, and no obvious urinary abnormalities have been reported.

Discussion

IMT is a tumor with “low malignant potential” or “borderline” characteristics, composed of myofibroblastic and spindle cells, and accompanied by inflammatory cell infiltration, such as lymphocytes, plasma cells, and eosinophils (1). Myofibroblasts in this tumor are the main cellular component, while inflammatory cells are scattered in the background of the tumor. IMT (9) was first described in 1939; however, it was not until the 20^th century and the 1990s (10) that the concept and classification of IMT gradually became clear. IMT can occur in various parts of the body (5), but the most common site is the lungs. In addition to the lungs, IMT can also occur in other organs and tissues, including the retroperitoneum, abdominal cavity, chest cavity, kidney, liver, pleura, bone, and soft tissue.

In terms of the age of onset, IMT is most common in children and adolescents (3), but it can occur at any age, and has a male-to-female ratio of about 2:1 (3). In this series of cases, we observed that the age of patients was distributed across all ages, which is consistent with literature reports. However, unlike previous reports in the literature, the gender ratio in this series of patients was equal; we believe that this difference may be due to the small number of patients in our study.

The pathogenesis of IMT is not fully understood (4) and may be related to inflammatory responses, infections, immune disorders, or other factors. IMT is a tumor with “low malignant potential” or “borderline” characteristics (11), and it only exhibits malignant behavior, with a risk of local recurrence and metastasis, in rare cases (12). Incomplete surgical resection is the most significant cause of recurrence and metastasis in IMT (13). In this case series, IMT recurred in two patients 3 years after surgical resection. These cases of recurrence might have been caused by unclear tumor boundaries or incomplete resection. In this study, imaging of the sacral IMT patient revealed multiple bone metastases throughout the body, with no clear evidence of a primary tumor in the internal organs. The tumor was thus considered to be of skeletal origin. Ultimately, the patient underwent resection of a right sacral mass due to hip pain. Postoperative pathological examination indicated IMT, leading to a diagnosis of IMT with multiple bone metastases. Combined with previous literature reports, this suggests that such tumors still carry a potential for metastasis. Following adjuvant therapy after surgery, the patient remains alive to date. Despite the malignant potential of this tumor, the majority of patients who undergo complete tumor resection can achieve clinical cure.

IMT can occur in any part of the body, but is most common in the lungs. When a patient has an unexplained mass, aberrant physical examination results, or associated site symptoms, the diagnosis of IMT may be appropriately investigated (14). Each patient’s symptoms are closely related to the location of the tumor. For example, if the site of the tumor is the lung, a patient may present with coughing, chest pain, breathing difficulties, and other symptoms. While if the site of the tumor is the abdomen, a patient may present with abdominal pain, indigestion, and other symptoms. Some patients may experience systemic symptoms, such as fever and weight loss. However, the symptoms of IMT patients are often not specific, and in most cases, tumors are accidentally found during other examinations (e.g., X-ray, CT, and MRI examinations) (15).

According to previous reports, IMTs range from 1 to 25 cm in size (15-17). In our study, the tumor diameter ranged from 2.0 to 9.5 cm, which is consistent with previous literature reports (15-17). Tumor size is not directly related to patient prognosis. However, a previous study found that patients with tumor diameters <6.5 cm have a higher survival rate than those with tumor diameters ≥6.5 cm (17). However, further research is needed to confirm this conclusion. In our case series, the patient with nasal IMT presented with a tumor larger than 6.5 cm upon admission and experienced multiple postoperative recurrences. The large size and challenging anatomical location of the tumor at the initial consultation likely increased the surgical difficulty and made complete resection more challenging, which may have contributed to the local recurrence of the tumor in this patient.

All six patients in this study underwent both CT and MRI examinations. Based on the findings from these cases and a review of previous literature, the imaging characteristics of IMT are summarized as follows. The imaging features of IMT are as follows: on a CT scan (6,7,18), IMT typically presents as a solitary, round, or lobulated mass, often appearing isodense or slightly hypodense with occasional calcifications. It usually has well-defined or partially defined borders. However, aggressive subtypes may exhibit infiltrative growth and can be accompanied by calcifications, hemorrhage, or necrosis. On contrast-enhanced CT, it shows mild or heterogeneous enhancement in the arterial phase and demonstrates persistent enhancement in the portal venous and delayed phases. On an MRI scan, on T1-weighted imaging, it predominantly appears isointense or slightly hypointense, while on T2-weighted imaging, the signal is highly heterogeneous, presenting a “cobblestone” or “whorled” pattern. This heterogeneity results from a mixture of densely cellular areas (hypointense), inflammatory/myxoid areas (hyperintense), and fibrotic regions (markedly hypointense) within the tumor. On diffusion-weighted imaging (DWI), the apparent diffusion coefficient (ADC) values are typically not low (or may even be mildly elevated), which differs from most malignant tumors, where high cellularity leads to reduced ADC values—a key distinguishing feature. Enhanced MRI is similar to CT in that it shows delayed, sustained, and non-uniform enhancement (19). On PET-CT scans, the maximum standardized uptake value (SUVmax) values of most IMT cases show mild to moderate uptake, which may present a “mismatch” between morphology and metabolism, presenting as soft tissue masses with clear boundaries and large volumes in morphology. However, their fluorodeoxyglucose (FDG) metabolic activity only shows a mild or moderate increase, which is helpful for differentiation from many highly metabolic invasive sarcomas (such as synovial sarcoma and rhabdomyosarcoma). It is the best tool for assessing whether there are multiple lesions or distant metastases, especially for cases that are invasive or recurrent at the time of diagnosis (20). The ultrasound manifestations of IMT are similar to those of MRI, which can present as extremely uneven echoes, with a vortex-like appearance (7). The imaging manifestations of IMT are diverse and non-specific, but certain features (such as the “cobblestone” sign on T2-weighted imaging and non-low ADC values on DWI) may suggest its possibility. Therefore, the final diagnosis of IMT needs to be confirmed by pathology and immunohistochemistry.

The pathological characteristics of IMT are as follows: cellular components (1): IMT is mainly composed of proliferating myofibroblasts and a large number of inflammatory cells (including lymphocytes, plasma cells, and eosinophils); cell morphology (1): myofibroblasts are usually spindle-shaped. Immunohistochemistry (8,21): in ≥50% of cases, one or more of SMA, vimentin, ALK, or desmin are positive. Among them, ALK is the most valuable diagnostic marker of IMT, and it has been reported that about 60–70% of cases express ALK (8,21). IMT usually has an ALK gene rearrangement (22), which increases the expression of ALK and may lead to the occurrence and development of tumors. The discovery of the ALK gene rearrangement represented a milestone in defining IMT as a tumor (23). A study also found that ALK inhibitors can be used as a first-line treatment option for adult patients with ALK-positive advanced IMT (24). Most IMT gross specimens are solid, well-defined grayish-white, or tan oval masses (15). Notably, the clinical manifestations of IMT are diverse, and IMT is easy to confuse with other diseases; thus, it is necessary to integrate pathologic, immunohistochemical, and molecular genetic information to ensure an accurate diagnosis. In this study, we presented six cases, all of which were positive for vimentin and SMA immunohistochemistry. Desmin immunohistochemistry was positive in 4 cases (66.67%). Two cases tested positive for ALK; however, the remaining four cases were not tested for ALK and thus could not be evaluated. The positive expression rate of Ki-67 in six IMT patients was 10–60%, and the proliferation index was relatively high, which might indicate that IMT has relatively active biological properties.

Based on our literature and clinical data analyses, the following information could play a certain role in the diagnosis of IMT: (I) it is more commonly observed in children and adolescents. and presents with mild or even no clinical symptoms in the early stage, but may present with tumor site-related symptoms in the late stage; (II) the tumor is a well-defined oval or irregular mass, mostly single, and generally a few centimeters to >10 cm in size; (III) on CT scans, it appears as a solitary, round, or lobulated mass with well-defined borders, showing isodense or mildly hypodense attenuation. On contrast-enhanced CT, it exhibits mild or heterogeneous enhancement during the arterial phase, with persistent enhancement in the portal venous and delayed phases; (IV) on an MRI scan, on T1-weighted imaging, it predominantly appears isointense or slightly hypointense, while on T2-weighted imaging, the signal is highly heterogeneous, presenting a “cobblestone” or “whorled” pattern; (V) histopathology typically reveals spindle cell proliferation and inflammatory cell infiltration; and (VI) immunohistochemistry usually shows one or more positive results for SMA, vimentin, ALK, or desmin. As IMT is relatively rare, there are few studies on it at home and abroad, and most such studies have been case reports. Larger clinical case reviews are needed to support these conclusions. In addition, IMT can also be diagnosed by percutaneous puncture biopsy (25), but biopsy may lead to tumor overflow, bleeding, and other adverse complications. The diagnosis of IMT follows an “imaging-pathology-molecular” three-step approach: after identifying a space-occupying lesion, pathology is obtained via biopsy or surgery. Diagnosis relies on typical morphology (spindle cells, inflammatory infiltration) and immunohistochemistry (ALK, etc.). ALK gene testing is recommended to guide treatment and prognosis evaluation. Finally, comprehensive risk stratification should be performed based on tumor location and biological behavior.

Preoperative imaging often cannot provide an accurate diagnosis. This is related to the small number of cases and the lack of characteristic imaging findings, which make it difficult to distinguish IMTs from other tumors before surgery. Preoperative imaging also cannot provide a further diagnosis. We comprehensively reviewed the literature and summarized some other diseases that are easily confused with IMT to improve the differential diagnosis of other diseases by preoperative doctors, reduce the overtreatment of patients caused by preoperative misdiagnosis, and assist in the formulation of reasonable treatment plans. IMT has a variety of imaging manifestations and may sometimes be confused with the following types of tumors: lung cancer (26): IMT often appears in the lung, and its image manifestations may be similar to lung cancer, which may present as a single lung nodule or mass with clear edges. Images show pulmonary parenchymal nodules or masses with blurred and irregular edges, calcification, cavities, necrosis, etc., accompanied by adjacent lymph nodes and distant metastases, pleural thickening, and pleural fluid accumulation, etc.; tuberculosis (26): imaging findings of IMT may be similar to those of tuberculosis, especially in cases of cavity formation or calcification in the lungs. The substantial lesions of lung tissue are often spotty and nodular; multiple lesions, multi-site distribution: these lesions are often irregular in shape with blurred edges. They can be accompanied by cavities, calcification, fibrosis, and other changes; hilar lymph node enlargement and calcification: these lesions may involve the pleura, mediastinum, and other sites; soft tissue sarcoma (27): IMT can appear in any part of the soft tissue, and its imaging findings may be similar to those of soft tissue sarcoma. The boundary of the mass is blurred, and necrosis, cystic change, and bleeding can be seen inside. The lesion is usually located in muscle or adipose tissue. Local infiltration and erosion of surrounding structures can be seen. Enhanced scans show moderate to obvious enhancement. It may be accompanied by peripheral lymph node enlargement and distant metastasis; lymphoma (28): IMTs may appear as multiple masses on imaging, and thus may be confused with lymphoma. The imaging features of lymphoma include lymph node enlargement, multiple foci, irregular shape, diffuse distribution, and low or high density; fibromas (29) and fibroids (30): the imaging findings of these tumors may be similar to those of IMTs, especially if the tumor has clear edges and a uniform internal structure. Fibromas are round or oval, with clear boundaries, uniform density, visible enhancement, and no adhesion to the surrounding tissue. Fibroids are round or oval, with clear boundaries and uniform density. They are often accompanied by calcification. There is no adhesion to the surrounding tissues. With the accumulation of clinical experience and the progress of science and technology, we have reason to believe that the preoperative misdiagnosis rate for IMT will be greatly reduced.

At present, the most effective treatment for IMT is the surgical resection of the tumor (8). When it is discovered, it typically has a bigger volume because it typically exhibits no overt signs of discomfort, and it is difficult to accurately diagnose and determine whether the tumor is benign or malignant before surgery. The specific mode of surgery should be determined according to the size of the tumor, its proximity to blood vessels and surrounding tissues, and the presence or absence of local invasion. Surgical operations should follow the “tumor-free” principle. During the operation, the tumor and the surrounding adherent tissues should be thoroughly removed. Complete resection is the key to possibly achieving a cure. Under the premise of preserving important functions, the resection range should be expanded as much as possible to ensure a negative resection margin. For recurrent or metastatic lesions, if technically feasible, reoperation can still be considered. For those with unresectable, metastatic, or high-risk recurrence conditions, drug treatment can be selected. The choice of first-line treatment depends on the ALK gene status. For ALK-positive patients, ALK tyrosine kinase inhibitors can be selected. For ALK-negative or unknown patients, chemotherapy can be chosen, and non-steroidal anti-inflammatory drugs may also be effective (4,8,24). Radiotherapy is usually not the main treatment method. It is mainly used for palliative care to relieve pain or compression symptoms for local lesions that cannot be operated on, or as an adjuvant treatment for patients with positive surgical margins after surgery who cannot undergo reoperation (17). Although IMTs usually do not invade neighboring organs, too large tumors can cause nearby structures to shift. In case 1, the tumor was located in the nasal cavity, and the tumor was large, resulting in a deviation of the nasal septum. In this study, the tumor in the nasal cavity IMT patient could not be completely resected, and despite combined repeated treatments, it ultimately led to multiple recurrences and even the patient’s death. In contrast, the upper arm IMT patient experienced postoperative tumor recurrence due to an insufficient initial resection margin but underwent a second surgical procedure at The Affiliated Hospital of Guizhou Medical University, during which the tumor was completely excised. Follow-up over several years has shown no recurrence. All other IMT patients in this series had their tumors fully resected, and long-term follow-up has confirmed no recurrence.

The first case of IMT was reported in 1939 (9). Since then, most IMT cases have been reported sporadically in the form of case reports, which lack statistical support. IMT is most common in the lungs but can occur in almost every organ. Independent risk factors affecting IMT may be related to the tumor location, size, positive tumor margin, and Ki-67 index. Postoperative tumor recurrence is closely associated with the status of the surgical margins. When Ki-67 exceeds 20% in tumor cells, it indicates active cell proliferation and usually indicates a poor prognosis. In this case series, Ki-67 reached or exceeded 20% in four patients, of whom two had recurrence after tumor resection, one patient had multiple systemic bone metastases, while the other patient had no recurrence or metastasis to date. At present, complete tumor resection is recommended by most scholars, but compared with adjuvant chemotherapy or radiotherapy, its survival benefit is still uncertain (17), and more clinical data are needed to confirm its use.

Our study had some limitations. Due to the rarity of IMT, only six patients were included in this single-center, retrospective study. Larger studies need to be conducted in the future to guide the diagnosis and treatment of IMT. The study had a number of advantages. First, to date, the total number of IMT cases reported in the literature has been small. Most of the IMT cases in the literature have been presented in the form of case reports, and most of the previous literature reports have only included imaging or pathological data of IMT. Therefore, we summarized the clinical data, imaging features, and pathological features of six cases of IMT to improve clinicians’ understanding of the disease. Second, since IMTs are difficult to distinguish from some other tumors in preoperative imaging, a correct preoperative diagnosis is particularly important for the treatment of IMT. We summarized the diagnosis and differential diagnosis of IMT based on our cases and searches of the latest literature. This study aimed to help doctors improve the rate of preoperative diagnosis of diseases and reduce the overtreatment of patients.

Conclusions

IMT is a tumor with “low malignant potential” or “borderline”, mainly requires radical surgical resection, and has a good prognosis, but as there is a possibility of recurrence, patients should be closely monitored. Its preoperative diagnosis is rather difficult, and it is prone to be confused with other tumors. When CT or MRI reveals a solitary mass with well-defined or ill-defined borders, particularly in young patients, and suggestive features such as a “cobblestone” pattern of high signal on T2-weighted imaging and non-low ADC values on DWI are present, the possibility of IMT should be considered. Pathology is the gold standard of diagnosis. When a patient cannot be treated surgically, and malignancy cannot be ruled out, it can be confirmed by a puncture biopsy, and guided diagnosis and treatment are required.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the AME Case Series reporting checklist. Available at https://tcr.amegroups.com/article/view/10.21037/tcr-2025-1-2571/rc

Peer Review File: Available at https://tcr.amegroups.com/article/view/10.21037/tcr-2025-1-2571/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tcr.amegroups.com/article/view/10.21037/tcr-2025-1-2571/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patients or legal guardians for the publication of this case series and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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(English Language Editor: L. Huleatt)