대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Inflammatory myofibroblastic tumor

Radiologic Findings

Fig 1. Chest radiograph shows an increased density in the area behind the heart and a silhouette sign of the left hemidiaphragm and descending aorta.
Fig 2-3. Chest CT images in a mediastinal setting show about 7x4x9 cm sized well-defined mass lesion in posterior basal segment of left lower lobe, abutting left pleura and invading left hemidiaphragm.
Fig 4-5. A 1-week later, chest CT images in the mediastinal setting show the mass increased in size (9x7x11 cm) with peripheral enhancement. There is no enlargement of lymph node in the mediastinum and both hilar.

Brief Review

The patient underwent VATS lobectomy of left lower lobe. From the operative findings, the mass was adhered to left pleura and left hemidiaphragm and had filled with dark brownish mucoid materials. Then, it had finally diagnosed as inflammatory myofibroblastic tumor.

Inflammatory myofibroblastic tumor is a neoplasm of intermediate biologic potential that frequently recurs and rarely metastasizes. It is composed of myofibroblastic mesenchymal spindle cells accompanied by inflammatory infiltration of plasma cells, lymphocytes, and eosinophils.
The etiology and pathogenesis of IMT are unknown, but several hypotheses have been proposed as an auto-immune mechanism or infectious origin. 30% of cases are closely related to recurrent respiratory infections, caused by several microorganisms such as Mycoplasma, Nocardia, Actinomycetes, Epstein Barr, and human herpes virus. Also, Coffin et al. found that about half of the IMTs have a clonal cytogenetic aberration which is involved in activation of the ALK-receptor tyrosine kinase gene. Their study reported that ALK reactivity may be a favorable prognostic indicator, and more likely to be associated with the atypical characteristics of IMTs.
Lung is one of the most common locations of IMTs. They account for around 50% of the benign pulmonary mass in children, representing only about 0.7% of all tumors of lung in general population.
Common clinical characteristics include unspecific respiratory symptoms, such as cough, chest pain, dyspnea, hemoptysis and unspecific inflammatory symptoms as fever, malaise and weight loss.
The radiological presentation of lung IMTs is nonspecific. They usually appear as solitary, well-circumscribed peripheral lung masses, with predominance for the lower lobes. Calcification of the masses is unusual (about 15 %). It is not frequent, but it can also be multiple. On CT with intravenous contrast, they present a variable heterogeneous or homogeneous degree of enhancement pattern. Pleural effusion is seen in less than 10% and atelectasis in 8% of cases. Sometimes the tumor can extend towards the hilum, mediastinum, pleura or diaphragm.
Because of the rather non-specific and variable radiological findings, there are many differential diagnoses for pulmonary IMTs including such as primary lung carcinoma and pulmonary metastasis, and benign tumors such as granuloma, hamartoma, and hemangioma. In our case, the initial radiological differential diagnosis included mesenchymal origin sarcoma, solitary fibrous tumor, and other malignant mass, such as lymphoma.
The treatment of choice for diagnostic and therapeutic reasons is complete resection. An incomplete resection increases the risk of recurrence. Corticosteroids are generally not useful in adults, although good results have been reported in children in cases of unresectable tumors or hilar and mediastinal invasion. Chemotherapy is useful in cases of multifocal, invasive lesions or in cases of local recurrence.

References

1. Jon Etxano Cantera et al. : Inflammatory myofibroblastic tumours: a pictorial review : Insights Imaging (2015) 6:85

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