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Revista chilena de pediatría

versión impresa ISSN 0370-4106

Rev. chil. pediatr. vol.90 no.3 Santiago jun. 2019 


Inflammatory myofibroblastic tumor: Variable presentation of the same pathology

Jorge E. Muñoz Moya1 

María Olga Alfaro Aguirre1 

Mauricio Leiva Silva1 

Elena Kakarieka Weisskopf2 

María Teresa López Sáez3  4 

1 Children's Surgery Service of the San Borja Arriarán Clinical Hospital, Chile.

2 Anatomopathology Service, San Borja Arriarán Clinical Hospital, Chile.

3 Urology service for children, San Borja Arriarán Clinical Hospital, Chile.

4 Children's Surgical Responsibility Center, San Borja Arriarán Clinical Hospital, Chile.



The inflammatory myofibroblastic tumor is an infrequent benign neoplasm with unpredictable cli nical behavior.


to describe three clinical cases at the San Borja Arriarán Clinical Hospital between March 2014 and January 2018 and to carry out an updated review of the literature.

Case 1:

14-year-old male adolescent, hospitalized due to abdominal pain, diagnosed with jejunojejunal intus susception secondary to an intestinal wall tumor. The histology was compatible with an inflamma tory myofibroblastic tumor.

Case 2:

12-year-old female adolescent, hospitalized due to pneumonia and low-back pain under study associated with weight loss. A retroperitoneal mass was diagnosed involving the right psoas muscle, paravertebral muscles, vertebrae, right kidney, and ipsilateral dia phragm. A puncture biopsy was performed and the result was compatible with an inflammatory myofibroblastic tumor.

Case 3:

11-year-old female pre-adolescent, hospitalized to study recurrent urinary tract infection. A bladder tumor was identified, and the biopsy showed compatibility with inflammatory myofibroblastic tumor.


Due to the variable behavior of the inflammatory myofibroblastic tumor, its management will depend on the location, expression of the anaplastic lymphoma kinase (ALK), tumor behavior, and the resection possibility.

Keywords: Inflammatory myofibroblastic tumor; tumor markers; surgical treatment


An inflammatory myofibroblastic tumor (IMT) is a benign tumor of intermediate biological behavior2,3. It is also known as inflammatory pseudotumor1, plasma cell granuloma, histiocytoma, xanthoma, fibroxanthoma, or inflammatory fibrosarcoma1,3,5,8.

It was first described in 1937 in a case with pulmo nary disease8,12 and has been reported in different ana tomical areas since then.

It occurs more frequently in infancy and in young adults2,3 and despite still having an uncertain etiology, it is associated with different factors such as trauma, in fections, genetics, and autoimmune pathologies1,3. The definitive diagnosis is histological3,4,5 and the treatment of choice is the surgical resection1,3,5.

Due to the infrequent nature of this pathology and the presence of three patients diagnosed with this tu mor at the Hospital Clínico San Borja Arriarán (HCS- BA), our main objective was to describe three IMT ca ses, diagnosed between March 2014 and January 2018. In addition, we will review and update the literature about this pathology.

Clinical Cases

Case 1

A 14-year-old male adolescent with no history of disease.

He consulted the Children’s Emergency Service due to a 7-days history of crampy abdominal pain and recurrent vomiting in the last 24 hours. The patient was evaluated on an outpatient basis and treated his symptoms without response, therefore, he consulted the HCSBA.

At admission, he was in poor general condition, dehydrated, and in a lot of pain. Resuscitation was ini tiated with saline solution, analgesics, and antiemetics. His tests showed: leukocytes: 15,240 x mm3; CRP: 1 mg/dl; liver profile in normal range; amylase: 197 mg/ dl; and creatinine: 1.52 mg/dl.

In abdominal x-ray (Figure 1A) was observed scar ce distal gas related to a stack of coins sign close to the mesogastrium and left flank (small intestine).

Figure 1 A) At the level of mesogas- trium and left flank small bowel loops can be seen with image in a stack of coins and little gas towards distal. B) je- junojejunal invagination secondary to intestinal wall tumor. C) Tumor seen on the endoluminal side. D) Sagittal section of the tumor that compromises the en tire wall of the jejunum. Homogeneous appearance and gummy consistency on palpation. 

The study was completed with abdominal ultra sound where a suggestive image of jejunal intussus ception secondary to polyp with proximal intestinal obstruction was observed.

The patient underwent an exploratory laparo tomy where jejunal intussusception was observed (Figure 1B), associated with a 5 x 3.5 cm mass in the intestinal wall, projected towards the lumen. Subse quently, en bloc resection was performed (Figure 1C and D).

The histology revealed ovoid to spindle-shaped tumor cells, elongated nuclei with moderate pleomor- phism and some histiocytoid cells of ganglion-like appearance with some mitosis, without intermixed atypical figures, with prominent lymphoplasmacytic inflammatory infiltration, and some eosinophils. In testinal wall presented tumor-free margins. Regarding immunohistochemistry tests, vimentin and alpha- SMA were positive; Ki-67 3% positive; CD68-positive in lymphoplasmacytic component, and anaplastic lymphoma kinase (ALK) weak to moderate positive in tumor cells. (Figure 2)

Figure 2 A and B HE staining. C: cyto plasmic positive ML actin in fused cells. D: ALK staining is weak to moderate positive in tumor cells. 

Lesion findings were consistent with IMT.

The patient continues in monitoring with oncolo gy after eight months of surgery, without recurrence episodes.

Case 2

12-year-old female adolescent, with hemoptysis history associated with weight loss and a 4-months low back pain history. She was hospitalized with a diag nosis of pneumonia, received antibiotic therapy and had a positive evolution. Due to the long-standing low back pain associated with weight loss, thoracic, abdo minal and pelvic tomography was performed which revealed retroperitoneal tumor involving right psoas, paravertebral muscles, bone infiltration into the spine, right diaphragm, and ipsilateral kidney.

After CT-guided needle biopsy, the sample histolo gy showed little to moderate cellularity, with spindle shaped cells of wavy and ovoid nuclei, and moderate infiltrate made up of lymphocytes, plasma cells, and histiocytes.

Regarding immunohistochemistry tests, vimentin, alpha-SMA, desmin, and myogenin were positive, and ALK was negative. The findings were consistent with IMT. (Figure 3)

Figure 3 A and C: HE staining. B and D actin ME positive in fused cells. 

Given the location and infiltrative component, the tumor was classified as unresectable, therefore, anti inflammatory therapy was initiated with Celecoxib 200 mg every 12 hours and Prednisone 20 mg every 12 hours. Although a partial reduction in tumor size was achieved, the patient continued with pain in the dorsal area, thus it was decided to add to the therapy Infliximab 300 mg IV every 24 hours in 0-2-6 weeks schedule. The patient presented an anaphylactic re action upon the second dose administration, there fore the use of methylprednisolone was required in the next cycle. Due to the adverse effects recurrence, Infliximab was replaced by another monoclonal anti body drug, Adalimumab, in doses of 40 mg SC every 15 days, associated with Celecoxib 200 mg every 12 hours and Prednisone 20 mg every 12 hours, achie ving absence of symptoms and a significant reduction in the tumor lesion size.

Case 3

11-year-old female pre-adolescent hospitalized due to repeated urinary tract infection (UTI) study. The abdominal physical examination showed a hypogastric mass.

Imaging studies were performed, where both ultra sound and abdominal CT (Figure 4A and B) showed a 7.8 x 5.5 x 5.7 cm solid vascularized cystic mass, in the posterolateral bladder wall. The lesion infiltrated the bladder wall and affected the mesentery in almost its entire pelvic extension (Figure 4C and D). Consi dering the radical cystectomy risk during the surgical procedure, it was decided to perform an incisional biopsy, whose histology was compatible with bladder IMT. Regarding immunohistochemistry tests, vimen- tin, desmin, alpha-SMA, cytokeratin, and ALM were positive, and ALK was negative.

Figure 4 A and B show TMI loca ted in the posterior bladder wall. C and D evidence of TMI displacing pelvic structures to the left. 

Treatment with COX-2 anti-inflammatory drugs associated with prednisone (there is no medication dose record) was indicated for approximately one year, achieving tumor remission. After the treatment period, an ultrasound was carried out identifying a residual lesion limited to a small segment of the bladder wall. Through cystoscopy, which showed a papillary lesion on the back side of the bladder (Figure 5A and B), the lesion was delimited, and a partial cystectomy was per formed with tumor-free margins. The biopsy (Figure 5C and D) showed a lesion compatible with IMT as sociated with Actinomyces israelii infection, which was probably the reason for the inflammatory reaction that causes the tumor. The patient was evaluated by the in fectious diseases department, starting antibiotic thera py with Sodium Penicillin IV for seven days and then Amoxicillin 1 g every 12 hours for six months with fa vorable response.

Figure 5 A and B cystoscopic ima ge of TMI. C and D muscular wall with smooth muscle infiltrated by myxobacterial myxoid tissue with foci of lymphoplasmacytic infiltrate and eosinophils. 

She currently remains in oncology monitoring, with no recurrence evidence.


IMT, also known as inflammatory pseudotumour1, is an infrequent benign neoplasm2,3,12, however, it is classified in the group of myofibroblastic tumors with intermediate behaviour4,6 due to its malignant potential, characterized by invasion of adjacent structures, recurrence, and future metastasis, where the latter is exceptional13,8.

It often occurs in children and young adults2,3,5,6, with a slight preference towards the male gender (M/F = 1.3/1)3.

Its etiology is uncertain but may be associated with trauma, surgeries, autoimmune pathologies, in flammation, and viral or bacterial infections such as the Epstein-Barr virus, herpes simplex virus, myco bacteria, and mycoplasma, among others. Genetic studies prove chromosomes translocation and genes fusion3,5,6,7,8,10.

This tumor is found in different anatomical áreas1,2,3, most frequently in the lung7,10. However, re cent studies described in (Table 1), show higher inciden ce in extra-pulmonary spots such as the abdominopel- vic cavity, where the liver is the main affected5. Atypical areas are also described8,9, such as the intestine, pan creas, genitourinary system, and bones.

Table 1 Anatomical location of inflammatory myofibroblastic tumor. 

The clinical presentation usually depends on the tumor location and may be asymptomatic2,11. Appro ximately 5 to 10% have systemic and physical manifes tations such as fever, weight loss, anorexia, microcytic and hypochromic anemia, hypergammaglobulinemia, and thrombocytosis (probably due to tumor produc tion of IL-1 and IL-6)4,5.

The lesion is generally single, although in 5% of ca ses it may be multiple5, and it is difficult to distinguish from other neoplasms through imaging studies1,2,5,6.

The definitive diagnosis is made with histology and immunohistochemistry studies7,9.

Three histological patterns have been described. The myxoid vascular pattern, the compact one of spindle-shaped cells with intermixed inflammatory cells, and the fibrous hypocellular one (dense collagen matrix predominance)3,4,5,13. Wang et al.3 showed that the spindle-shaped cell pattern was the most frequently represented in 96% of cases.

Microscopic study is not enough to differentiate it from other tumors such as stromal, leiomyosarcoma, and inflammatory malignant fibrous histiocytoma, so immunohistochemistry study is necessary to confirm the diagnosis. Mesenchymal cells are usually immuno-reactive for vimentin, desmin, alpha-SMA, and S1008 protein and negative for c-kit12.

Up to 71% of these tumors are positive for ALK- 18,12, which gives IMT greater susceptibility to drug treatment than those who do not express it4, but with a higher recurrence rate8. Genetic studies have determined that 50% of IMT will have an alteration in the ALK gene structure (chromosome 2p23), generating different fusion patterns7,9,14.

Tateishi Y et al.9 present a case of intraosseous IMT, where an ATIC-ALK fusion is identified through the FISH (fluorescence in situ hybridization) method.

Differential diagnosis is made with benign lesions such as giant cell granuloma, solitary fibrous tumor, myoepithelioma, myxofibroma7,9, and with malignant tumors such as low-grade myofibroblastic sarcoma, teratomas, rhabdomyosarcomas, and lymphomas3,7.

The IMT management will depend on its location, the ALK expression, its behavior, and the surgical re section feasibility.

In relation to behavior, cases of local infiltration, recurrence, and metastasis are described, however, there are also publications reporting spontaneous resolution6,12.

Zhao et al.6 presented two cases of adult patients diagnosed with an intra-abdominal inflammatory myofibroblastic tumor, cataloged as unresectable, and that regressed without any treatment. In addition, they presented a systematic review with a total of 36 pa tients with intra-abdominal tumors which presented spontaneous regression without surgical intervention6. The reason for spontaneous regression is not clear, but three factors are proposed that could influence:

1. Lesion location: Liver lesions have a better prog nosis compared to those located elsewhere in the abdomen, pelvis, or retroperitoneum.

2. Age of presentation: regression was more frequent in middle age and older patients.

3. Other factors such as aneuploidy, atypia, and gan glion-like cells were associated with increased re currence and malignant transformation6.

In relation to the therapeutic approach based on the inflammatory origin hypothesis, cases of non-ste roidal anti-inflammatory drugs and corticosteroids use have been reported12. It is suggested that anti-inflammatories would have an inhibitory effect on angiogenesis and cell proliferation through the induction of fibroblast apoptosis and therefore may inhibit tumor vascularization, endothelial proliferation, and tumor growth12. Tsuma et al. presented the case of a 13-year- old adolescent with IMT diagnosis, treated with COX- 2 inhibitors and prednisolone, achieving a reduction in the lesion size for later resection. Immunohistochemical analysis revealed COX-2 tumor expression which justified the selective COX-2 inhibitors efficacy in re ducing tumor size14.

The literature describes two cases of patients who did not respond to anti-inflammatory therapy and it was decided to use Infliximab, obtaining a favorable response and achieving lesions stability and a decrease in symptomatology in one of the cases12, and almost complete mass regression, associated with the sympto matology absence in the other one13.

The role of radiotherapy and chemotherapy is not yet clear4,12 since it has not shown a definitive benefit5, therefore, the treatment of choice is surgical resection which is healing1,3,5,8,12.

Recurrence ranges from 25 to 40% and is more fre quent in extra-pulmonary lesions and during the first year after resection3,5,7. If the removal is complete and the lesion shows tumor-free margins, the recurrence rate is less than 10%3. Metastases are infrequent and around 2%8,11.

The characteristics that can predict a worse prog nosis, recurrence and metastasis probability are female gender, age over 25 years, abdominopelvic location, large size, multinodular mass, incomplete resection, and ALK negative12.

Dalton B. et al. evaluated 32 patients with IMT diagnosis, determining a higher association with mor tality the disease persistence and recurrence (67 vs 0%)1.

Regarding follow-up, ultrasound monitoring is su ggested after resection, at 3, 6 and 12 months1,3.


IMT is classified as an intermediate behavioral myofibroblastic tumor. Its clinical manifestations are diverse and will be determined by the affected anato mical area. Management will depend on its location, ALK expression, behavior, and surgical resection fea sibility.

In this work, three cases were presented with di fferent clinical manifestations, management, and re sults, which supports the diversity of this entity. Until the review, the use of monoclonal antibodies is des cribed in only three patients worldwide, and our case is the second described in Chile. Although its results seem to be encouraging, more studies are needed to establish it as a therapy scheme in the management of ALK-negative IMT that is not susceptible to surgical resection.

Ethical Responsibilities

Human Beings and animals protection: Disclosure the authors state that the procedures were followed ac cording to the Declaration of Helsinki and the World Medical Association regarding human experimenta tion developed for the medical community.

Data confidentiality: The authors state that they have followed the protocols of their Center and Local regu lations on the publication of patient data.

Rights to privacy and informed consent: The authors have obtained the informed consent of the patients and/or subjects referred to in the article. This docu ment is in the possession of the correspondence author.

Financial Disclosure: Authors state that no economic support has been asso ciated with the present study.

Conflicts of Interest: Authors declare no conflict of interest regarding the present study.


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Received: September 21, 2018; Accepted: March 07, 2019

Correspondence: Jorge E. Muñoz M. E-mail:

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