Inflammatory myofibroblastic tumor of lung in an adult female—a rare case

Abstract

Inflammatory myofibroblastic tumor occurs primarily in the viscera and soft tissue of children and young adults. This tumor is potentially malignant because of its tendency for local recurrence and its ability to metastasize. It is composed of a variable mixture of collagen, inflammatory cells, and usually bland spindle cells showing myofibroblastic differentiation. We report a 38-year-old female diagnosed with inflammatory myofibroblastic tumor preoperatively and has undergone right upper and middle lobectomy through fifth intercostal space for the same. Post-operative histopathology corroborated with preoperative diagnosis.

Introduction

Inflammatory myofibroblastic tumor (IMT) is a rare benign tumor accounting for 0.7% of all lung tumors [1, 2]. It was first described by Brunn in 1939 [3]. Its origin is unknown, but recent studies have shown that it is a true tumor rather than a reactionary process [1, 4]. They are also known as “plasma cell granuloma,” “histiocytoma,” and “fibroxanthoma” depending on the predominant cell type.

The standard procedure, for both diagnosis and treatment, is surgical resection. They have the capacity for local invasion, rapid growth, and sarcomatous transformation. Non-surgical modalities have been employed in patients in whom resection was incomplete, in whom there has been recurrence, or who are poor surgical candidates. Spontaneous regression is extremely rare.

Its clinical and radiological manifestations are protean. That is why diagnosis is difficult to establish unless a surgical resection or tissue sampling is performed followed by histopathological examination and immunohistochemistry is done [2].

It is the most common lung tumor below 16 years of age and the most common endobronchial mesenchymal lesion in childhood [1]. Inflammatory myofibroblastic tumor has an equal sex distribution and occurs in all ages, though most occur in individuals less than 40 years.

Case report

A 38-year female patient was referred from the chest department with the diagnosis of space-occupying lesion (SOL) in upper lobe of the right lung.

Patient had a history of recurrent lower respiratory tract infection (LRTI), diffuse right-sided chest pain, and occasional hemoptysis for last 1 year. Pulmonary tuberculosis was ruled out by routine investigations in the chest OPD because pulmonary tuberculosis is a very common disease in our region and it is a great imitator. Chest X-ray showed a homogenous opacity invading the entire upper lobe of the right lung. Computed tomography (CT) scan of chest showed a tumor of 8 cm diameter in upper lobe with partial atelectasis of middle lobe of the right lung (Fig. 1a, b).

Fig. 1.

a Chest X-ray PA view showing SOL in right upper lobe. b CT scan of chest showing large SOL in right upper lobe

Bronchoscopy showed partial occlusion of right main bronchus by an extra-luminal mass which was also supported by CT scan (Fig. 2). Microscopic examination of CT-guided trucut biopsy showed proliferation of regular spindle cells arranged in fascicles, admixed with lymphocytes, plasma cells, and eosinophils. Immunohistochemical analysis showed positive staining for ALK1 and Vimentin. Based on these data, the diagnosis of inflammatory myofibroblastic tumor was made, and after consultation with multispeciality tumor board, as per our institutional protocol, surgical resection was planned.

Fig. 2.

CT scan showing (red arrow) compression of the right main bronchus by SOL

After routine preoperative investigations and optimization, patient underwent right upper and middle lobectomy through standard right posterolateral thoracotomy through fifth intercostal space (ICS). Latissimus dorsi preserving thoracotomy has advantage in terms of reduced morbidity to the patient, but the surgeon found it convenient to divide latissimus dorsi for proper exposure and manipulation of the centrally located tumor. There was no obvious fixity of the mass to the parietal pleura or adjacent structures. But the mass was apparently very large, and it was close to hilum and involved the whole of right upper lobe with involvement of the incomplete fissure between upper and middle lobe causing atelectasis of a portion of middle lobe. Therefore, taking into consideration the chances of recurrence, we decided to remove right upper and middle lobes. Pulmonary veins and pulmonary arteries were separately dissected, transfixed with 5–0 polypropylene, doubly ligated with 3–0 silk, and divided. The right upper lobe and middle lobe bronchi were taken out and closed with 5–0 polypropylene separately (Fig. 3a–c).

Fig. 3.

a SOL in right upper lobe after thoracotomy. b Bronchial stump after tumor excision. c Cut open specimen showing homogeneous tumor mass

Patient recovered uneventfully and was discharged on seventh post-operative day. Post-operative histopathological report confirmed the diagnosis of inflammatory myofibroblastic tumor.

Discussion

The varying terminologies used to describe the inflammatory pseudotumor of the lung, like plasma cell granuloma, inflammatory myofibroblastic tumor, histiocytoma, fibroxanthoma, xanthogranuloma, and plasma cell histiocytoma complex, have caused a great deal of confusion in understanding the natural history of the disease. Umiker and Iverson preferred to include all these lesions under the designation of inflammatory pseudotumor since morphologically these simulate a tumor and histologically these are composed of inflammatory cells and show complete maturity of fibroblasts.

It is a non-neoplastic process characterized by unregulated growth of inflammatory cells. The cause of this inflammatory response remains unknown, and various theories attribute this to a metabolic disturbance, organized cellular growth developing in association with pulmonary infection, viral origin, or antigen-antibody interaction in relation to an agent, which is no longer identifiable [5].

The role of antibiotics has been speculated upon. However, neither bacteria nor fungi have been grown in tissue cultures in any of the resected specimens but a history of prior infection could be obtained in about one third of patients [5].

Grossly, they are round, well-circumscribed but unencapsulated intrapulmonary masses. Microscopically, they are circumscribed tumefactive lesions, composed of a variable mixture of collagen, inflammatory cells, and benign mesenchymal cells including spindled myofibroblasts, fibroblasts, plasma cells, lymphocytes, foam cells, giant cells, and macrophages.

Inflammatory myofibroblastic tumor of the lung is benign tumor of childhood. The reported incidence in various reports varies from 0.04 to 0.7% of lung masses [5]. Though usually reported in pediatric age group, they may occur at any age. It is the most common primary lung mass seen in children. There is no sex predilection [6].

The symptomatology of the tumor is generally in the form of cough, chest pain, dyspnea, and hemoptysis and is generally non-specific. Fever and clubbing have been observed particularly in younger patients and generally disappear after resection of the lesion [5]. The laboratory data are not of much help in diagnosis of inflammatory myofibroblastic tumor. The most common radiographic presentation is that of a solitary well-circumscribed round or oval pulmonary mass. This is seen in over 50% of patients. Approximately 25% of patients will present with a coin lesion [7]. The tumor size may range from 0.5 to 36 cm. The pulmonary mass can grow quite large, occupying the entire lung.

Calcification is not infrequent in inflammatory myofibroblastic tumor of the lung. The nature of calcification in inflammatory myofibroblastic tumor is most commonly described as mottled with calcific flecks and is thought more often to be fine in nature rather than course. Dense calcification has also been reported.

A small group of patients may present with ill-defined areas of pneumonic consolidation or atelectasis. In most cases, the lesion is usually intra-parenchymal with secondary compression and entrapment of bronchi occurring with growth [7]. Occasionally, endobronchial and endotracheal lesions may cause post-obstructive pneumonia or atelectasis. Rarely, multiple lesions are present. Central cavitation is a very unusual feature. Hilar lymphadenopathy is rare and pleural effusion has not been reported to occur with this etiology [7].

Inflammatory myofibroblastic tumor can manifest as a mediastinal mass. Aggressive features of these have been described, including vertebral destruction, vascular invasion [8], recurrence [9], and metastatic spread [10]. There is considerable diversity of appearance of these tumors on CT scan in cases that have been studied so far. CT scan most commonly demonstrates a mass of heterogeneous attenuation. Variable enhancement patterns have been described on contrast enhanced CT scans, including non-enhancement, mild enhancement, heterogeneous enhancement, and peripheral enhancement. Variable calcification patterns have been described on CT scans including punctate, dense, flocculent, and curvilinear [6].

A study of magnetic resonance imaging (MRI) findings in five patients of inflammatory myofibroblastic tumor showed heterogeneous lesion with signal intensity slightly greater than skeletal muscles on T1-weighted images and high signal intensity on T2-weighted images. Diffuse heterogeneous enhancement of the lesion was noted on gadolinium-enhanced images [6]. The radiological differential diagnosis includes primary neoplasm, metastasis, hamartoma, chondroma, sclerosing hemangioma, and pulmonary granuloma. Endobronchial inflammatory pseudotumor may mimic carcinoid [6].

Resection of the lesion is treatment of choice. However, non-surgical treatments like radiotherapy and steroids have been employed in the setting of incomplete surgical resection, tumor recurrence, and patient being unfit for surgery [5].

Conclusion

In conclusion, inflammatory myofibroblastic tumor of lung is a relatively uncommon lesion, which is typically solitary, peripheral, sharply circumscribed, lobulated mass. Most patients are symptomatic at diagnosis and may have a history of prior lower respiratory tract infection. The radiographic and CT appearance of inflammatory myofibroblastic tumor is quite variable and non-specific. Therefore, when clinical presentation of pulmonary neoplasm or infection is atypical or problematic, surgeons should consider the diagnosis of inflammatory pseudotumor, to be aware of the variety of its different radiographic and CT manifestations.

Inflammatory myofibroblastic tumor is a rare benign tumor. Clinical and radiological presentation is variable and non-specific and the diagnosis is rarely made before surgical management. Only histological and immunohistochemical study can confirm the diagnosis. Though it is a benign lesion, its potential for recurrence and local invasion requires complete surgical resection.

Authors’ contribution

All the authors have contributed to the study concept, design, data collection, data analysis for interpretation, and writing this manuscript.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

All procedures performed in study were in accordance with the ethical standards of the institutional and national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Consent

Informed consent was obtained from the patient to publish this report for academic interest.