Inflammatory myofibroblastic tumors are uncommon tumors; they usually present as solitary masses in the pulmonary parenchyma. Involvement of trachea by myofibroblastic tumors is a rare occurrence. Tracheal tumors are often misdiagnosed as obstructive airway disease in adults and foreign body aspiration in children. A high index of suspicion including bronchoscopic examination is required for diagnosis. Herein, we report the case of a 15-year old girl who was initially misdiagnosed with bronchial asthma and finally diagnosed to have tracheal inflammatory myofibroblastic tumor. We have also conducted a systematic review of the literature on tracheal inflammatory myofibroblastic tumor reported in children.
A 15-year-old girl presented to the emergency department with complaints of dry cough and breathlessness of 4 months duration. Over 4 months the breathlessness worsened and her activities of daily living became limited. She also noted wheezing sounds and found that her breathlessness was partly relieved in the sitting position. There was no history of hemoptysis. She presented to the emergency department with acute worsening of her dyspnea. The patient was initially diagnosed to have severe acute asthma and treated with inhaled bronchodilators and parenteral steroids. However, she did not respond to treatment and developed type 2 respiratory failure. She was endotracheally intubated and mechanically ventilated. Over the next 2 days, she improved, was extubated, and discharged with a label of bronchial asthma.
Within the next few days, her symptoms reappeared and now she was referred to our clinic for evaluation. Lateral soft tissue radiograph of the neck showed the presence of a soft tissue mass compressing the superior part of the trachea from the posterior aspect (Fig. 1). This was confirmed by a computed tomographic scan, which demonstrated a broad-based growth arising from the posterior wall of the trachea 1 cm below the vocal cords, approximately 1.7 cm in length (Fig. 2). She underwent flexible bronchoscopy for further evaluation, which also demonstrated a growth arising from the posterior wall of the trachea just below the vocal cords with 70% luminal obstruction. For diagnostic and therapeutic purposes, she underwent rigid bronchoscopy under general anesthesia (Fig. 3). The tumor was “cored” with the bevel of the rigid scope and removed with an optical biopsy forceps (Fig. 3); the tissue retrieved was sent for histopathologic examination.
Histology revealed a mixture of spindle cells showing fibroblastic and myofibroblastic differentiation arranged in short fascicles and a storiform pattern. The spindle cells had oval nuclei, fine chromatin, inconspicuous nucleoli, and bipolar, lightly eosinophilic cytoplasm. The background showed large areas of hyalinization and scanty inflammatory infiltrate comprising of lymphocytes and plasma cells (Fig. 4). Immunohistochemical analysis showed patchy cytoplasmic positivity for smooth muscle actin and diffuse cytoplasmic positivity for ALK (Fig. 4). IgG4 immunostain did not reveal any IgG4-positive plasma cells. On the basis of morphology and anaplastic lymphoma kinase (ALK) positivity, a diagnosis of inflammatory myofibroblastic tumor was made.
Post procedure the patient had symptomatic improvement. A repeat radiograph of the neck showed significant reduction in the intraluminal growth (Fig. 1B). She was discharged with an advice to undergo a surgical resection, which the patient and the parents refused. She is symptom free at 6 months follow-up.
We systematically searched the PubMed and EmBase databases using the following free text terms: inflammatory pseudotumor OR pseudosarcomatous myofibroblastic proliferation OR plasma cell granuloma OR xanthomatous pseudotumor OR inflammatory myofibrohistiocytic proliferation OR inflammatory fibrosarcoma OR inflammatory myofibroblastic tumor OR fibroxanthoma OR histiocytoma OR fibrous histiocytoma OR xanthomatous pseudotumor OR postinflammatory pseudotumor OR mast cell tumor OR plasma cell-histiocytoma complex AND trachea OR bronchi OR bronchus OR airways OR airway OR respiratory tract OR respiratory system. Separate searches were also carried out for “inflammatory myofibroblastic tumor” and “tracheal tumor.” In addition, we searched our personal files. The searches were limited by the following: English, age below 18 years. We included case reports and case series published in the last 4 decades on inflammatory myofibroblastic tumor.
Inflammatory myofibroblastic tumor (IMT) was first described in 1939 by Brunn and colleagues and christened the current term by Umiker and colleagues in 1954, as it imitated a malignant tumor.1 Although it represents only 0.7% to 1% of all bronchopulmonary neoplasms, it is the most common pulmonary neoplasm in children below 16 years of age.2 There has been a confusion with regard to its etiology and exact status, which is reflected in the multiple terms the tumor carries, namely plasma cell granuloma, inflammatory pseudotumor, inflammatory fibrosarcoma, pseudosarcomatous myofibroblastic proliferation, xanthomatous pseudotumor, inflammatory myofibrohistiocytic proliferation, and inflammatory fibrosarcoma.1,3
The etiology of this tumor has not been clearly defined. In the earlier literature it was thought to be a reactive process rather than a tumor, hence the name “pseudotumor.” Presently, it is believed to be a low-grade benign tumor characterized by the presence of a clonal population of cells; however, it has been known to occasionally behave in a locally invasive manner and even to metastasize.4 The histopathologic appearance is characterized by the presence of myofibroblastic spindle-shaped cells in the background of an inflammatory cell infiltrate consisting of lymphocytes, plasma cells, and eosinophils. The cells are nonreactive for IgG4, which excludes IgG4-related pseudotumor, a close differential diagnosis.5–7
Recently, these tumors have been found to be positive for the ALK gene rearrangements. The ALK gene is located on the chromosome locus 2p23 and codes for a receptor tyrosine kinase belonging to the insulin receptor superfamily. ALK kinase activity has been inversely correlated with promotion of apoptosis, and ALK gene rearrangement has been demonstrated in multiple malignancies including anaplastic large cell lymphoma, small cell carcinoma of the lung, neuroblastoma, and some rare sarcomas and carcinomas. About 50% of IMTs are positive for the ALK translocation and this is more common in younger patients. There is no clear correlation between ALK expression and prognosis or recurrence, although some studies have demonstrated a better prognosis with ALK expression.8 Our patient was found to be positive for ALK expression.
Clinically, these tumors are mostly found in the lung with other common sites being the orbit, the peritoneum, and the mesentery. However, they may be found in almost any site in the body.2,3,9,10 In the lung, they are commonly found in the pulmonary parenchyma; primary tracheal tumors are rare.2,3 In the tracheobronchial tree the tumors may be asymptomatic or present with features of airway obstruction, recurrent pneumonias, or asthma.11,12 As in our case, the patient may be misdiagnosed as asthma. Systemic symptoms may or may not be present; they are attributed to the secretions of cytokines, especially interleukin-1.1
A systematic review of the literature yielded 52 cases of tracheal IMTs reported in children.2,13–55 The tumor was found to be more common in the upper trachea and presented with symptoms of endobronchial disease such as cough, hemoptysis, dyspnea, and wheeze. A few of these patients were misdiagnosed as suffering from bronchial asthma and treated accordingly (Table 1). Radiologically, pulmonary IMTs present as lobulated masses with sharp distinct margins in the peripheral parenchyma with a heterogenous attenuation and enhancement. They have a predilection for lower lobe involvement. Calcification has also been noted. Less common presentations include central masses, pleural based nodules, and mediastinal lymphadenopathy.1 Although these tumors are benign, invasion of local structures, especially the vertebra and thoracic vessels may occur.12 The recurrence rate of these tumors varies from 8% to 24% and recurrences can occur anywhere from 1 to 24 months.12 We found that 36 of the 52 cases we reviewed responded to primary treatment, either surgical or bronchoscopic (Table 2), whereas recurrence was seen in 9 cases (Table 3). The prognosis is generally good if the tumor has been removed completely.
The treatment of IMTs is surgical removal wherever possible because of the risk of malignant transformation.12 This holds true for all primary tracheal tumors, as well. Although there are some reports on IMTs being managed with therapeutic bronchoscopy alone,2,14,26,41,53,54 we found at least 5 instances in which bronchoscopy had to be followed up with surgery for either complete removal or recurrence (Tables 1, 2).31,36,44,47 Thus, therapeutic bronchoscopy has a limited role in management of these tumors. In patients presenting acutely with respiratory symptoms, the rigid bronchoscope can be used to debulk the tumor for relief of airway obstruction, as was done in our case.3
The discovery of the presence of ALK gene rearrangements in IMTs raises the possibility of treatment of these tumors by ALK inhibitors. A report published in 2010 demonstrated that crizotinib, an ALK inhibitor, induced partial remission in a patient of IMT who was positive for the ALK mutation.56 Moreover, cyclo-oxygenase 2 inhibitors, especially celecoxib, have been demonstrated to induce remission in ALK-negative individuals.57,58 The potential of these upcoming treatments is enormous, and further studies are required to fully inculcate them into the therapeutic algorithm.
In conclusion, tracheobronchial tumors are rare in children, the most common being IMT. The closest histologic differential diagnosis is inflammatory pseudotumor, which is IgG4-positive. Fifty percent of IMTs are positive for ALK gene rearrangements. Treatment involves surgical resection. Endobronchial treatment is required only in emergency situations and in those unwilling for surgery. New and upcoming treatments include ALK inhibitors like crizotinib.
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