Inflammatory myofibroblastic tumour of the lung in a young male

A 36-year-old male patient, a former smoker, with a history of left radical orchidectomy for seminoma, performed a chest radiograph during a routine follow-up. The radiograph showed a well-circumscribed nodule in the left lower lobe (Figure 1). A computed tomography (CT), a PET-CT and a biopsy were later performed for better characterisation.

A computed tomography without contrast was performed, identifying a well-circumscribed 17 mm solid nodule in the left lower lobe (Figure 2). There was no evidence of macroscopic fat, and no intra-lesional calcifications were noted. A subsequent [18^F]-FDG-PET-CT was performed, showing a nodule in the left lower lobe, which was mildly FDG-avid. There were no other pulmonary lesions nor evidence of thoracic adenopathies or distant metastasis. Consequently, a thoracic biopsy was performed, and the histological results were suggestive of an inflammatory myofibroblastic tumour (IMT). Left lower lobectomy was proposed to the patient. In the pathological examination, a mesenchymal neoplasm was identified, confirming the diagnosis of IMT (Figures 3 to 6). One year after the surgery, chest CT did not reveal new nodules or other relevant changes, and the patient is asymptomatic.

Background

First described by Brunn in 1937, inflammatory myofibroblastic tumours (IMTs) are a rare group of neoplasms composed of a mixture of spindle-shaped myofibroblasts and inflammatory cells. One of the most frequently affected organs is the lung [1,2]. Although it is the most common lung tumour in children, it is rarely seen in adults, with equal male and female incidence rates [3]. The pathogenesis is still unclear, although different aetiologies have been proposed, such as chronic infections, autoimmune diseases, and trauma [1,4]. In some cases, IMTs are also related to previous lung surgery, and they can arise in surgical lung scars [2].

Clinical Perspective

Patients can be asymptomatic or present with unspecific respiratory symptoms, such as cough, dyspnoea, fever and malaise [1–4].

Imaging Perspective

The radiological presentation of lung IMTs is non-specific, and they are often misdiagnosed as malignant neoplasms. They usually appear as solitary, well-circumscribed peripheral lung masses, with predominance for the lower lobes. They may also involve the pleura, showing pleural retraction in these cases [4]. Calcification of the masses is unusual and more common in children than in adults, while cavitation and lymphadenopathy are rare [1,2]. Although uncommon, they can also be multiple. On chest radiograph, they are normally single, well-defined, oval lesions and on contrast-enhanced CT, they show variable enhancement on delayed acquisitions due to the presence of fibrosis. On MRI, a notable feature is its hyperintensity on T2-weighted images due to the myxoid stroma. Although FDG-PET/CT shows variable FDG uptake by IMT in the lung, this modality may be best suited for the evaluation of local recurrence and distant metastases [1–3]. Nevertheless, histopathologic examination of the resected specimen is the only reliable method to confirm the diagnosis. Positive immunohistochemical staining of ALK is seen as a prognostic factor of aggressiveness, and it is present in approximately 40–100% of IMTs [4].

Outcome

Surgical resection is both diagnostic and curative in most cases of solitary pulmonary IMT, with an excellent prognosis after complete resection. Cases of spontaneous regression or resolution after treatment with corticosteroids have been reported. In case of incomplete resection or non-operable patients, radiotherapy is an alternative treatment. The prognosis after complete surgical resection is excellent, with a low rate of recurrence [2,3].

Take Home Message / Teaching Points

Lung inflammatory myofibroblastic tumours are a rare group of neoplasms, and their radiological presentation is non-specific. They usually appear as solitary, well-circumscribed peripheral lung masses, with predominance for the lower lobes. Surgical resection is both diagnostic and curative, and the prognosis after complete resection is excellent [1–4].