CASE 13154 Published on 16.11.2015

Inflammatory Myofibroblastic Tumour (IMT) of the lung

Section

Chest imaging

Case Type

Clinical Cases

Authors

Bettini G.1, Sheaff M.T.2, Ellis S.3

1 Resident Fellow, Department of Medical, Surgical and Neuro Sciences, University of Siena; gloriabttglr@gmail.com
2 Consultant Histopathologist, Department of Histopathology, Barts and The London NHS Trust, London, UK
3 Consultant Radiologist, Diagnostic Imaging, Barts and the Heart Centre, West Smithfield, London EC1A 7BE; stephen.ellis@bartshealth.nhs.uk

Santa Maria alle Scotte,University of Siena,Department of Medical, Surgical and Neuro Sciences; Viale Bracci 10 53100 Siena; Email:gloriabttglr@gmail.com
Patient

27 years, male

Categories
Area of Interest Thorax ; Imaging Technique Digital radiography, CT, Experimental
Clinical History
An asymptomatic non-smoking 27-year-old male patient presented with a positive Quantiferon test performed for latent TB screening and went on to have a Chest X Ray (CXR) to exclude active TB.
Imaging Findings
PA-CXR demonstrated a large solitary nodule projected behind the right hemidiaphragm, with no evidence of cavitation, calcification or adjacent lung parenchymal abnormality [Fig. 1a]. Lateral-CXR confirmed this posteriorly in the right lower lobe [Fig. 1b].
The patient underwent non-contrast-CT, through the lesion, followed by a post-contrast-CT of chest and abdomen. CT was performed with a 64-row CT-scanner (Siemens Healthcare, UK). Acquisition parameters used in spiral CT acquisitions were: 120kV and 110mA, with iterative reconstruction. The contrast medium was Omnipaque300.
CT images confirmed the presence a well-defined lesion, with smooth margins, in the postero-basal segment of the right lower lobe, with no calcification or cavitation, but heterogeneous enhancement, pre-contrast density was 16HU (SD 7.8), post-contrast density was 50 HU (SD 23) [Fig. 2-6].
No other abnormality was seen on CT.
CT-guided biopsy was performed and a histopathological diagnosis of inflammatory myofibroblastic tumour of the lung was made [Fig. 7].
The patient underwent surgical resection.
Discussion
Inflammatory Myofibroblastic Tumors (IMT) were first described in the lung by Brunn in 1939 [1].
In 2002, the World Health Organization (WHO) classification defined IMT as a distinctive lesion composed of myofibroblastic spindle cells with an inflammatory infiltrate of plasma cells, lymphocytes and eosinophils [2].
Despite being considered a non-malignant lesion, according to an update based on the latest (4th edition) WHO classification of soft tissue tumor done in 2013, IMT is classified as a true neoplasm rather than a reactive process [2, 3, 4].
Mutations of Anaplastic Lymphoma Kinase (ALK) gene and ALK-receptor gene are observed in approximately 40-100% of IMT, depending on the anatomical site where it arises [5, 6].
A relation between IMT and IgG4-Syndrome has been reported in the literature [5], even though Bhagat et al. tried to distinguish IMT and IgG4-related inflammatory pseudotumour [7].
The lungs are the commonest site for IMT, but involvement of orbits, gastro-intestinal and genitourinary tract also occurs [5]. IMT is found most commonly in children and young adults, has no gender or racial prediliction, and is extremely rare (0.04-1% of all lung tumours) [2].
Pulmonary IMT (PIMT) represents a low grade malignant lesion, with slow and local growth [5]. However, a more aggressive behaviour with distant metastatic spread has been described and for this reason resection was thought to be prudent [8].
Patients with IMT are usually asymptomatic, as in our case, or may present with non-specific symptoms [2].
PIMT usually appear as a solitary, well-circumscribed peripheral lung mass, with a predominance for the lower lobes [6].
Calcification of the mass is unusual, the presence of intralesional calcium can occur in up to 15% of cases [9].
On CT there is an heterogeneous or homogeneous enhancement pattern [6].
Some authors described the possibility of atypical Hypertrophic Pulmonary Osteoarthropathy (HPO) in PIMT patients, with abnormal periosteal formation [2].
Local expansion may cause significant morbidity and occasional death. The treatment of choice of PIMT is surgery. The prognosis after complete surgical resection is excellent [6].
A broncoscopic resection can be an useful alternative to surgery [10].
In cases of extensive involvement or inoperable patients (patients with poor pulmonary function and comorbidity) radiotherapy, corticoids and chemotherapy may be employed [6].
PIMT, although rare, should be considered in the differential diagnosis for an incidental peripheral pulmonary mass or nodule seen on CXR or CT in patients typically under 40 years old.
Differential Diagnosis List
Inflammatory myofibroblastic tumour.
Endobronchial carcinoid tumour
Adenoid cystic carcinoma
Mucoepidermoid carcinoma
Granuloma
Hamartoma
Final Diagnosis
Inflammatory myofibroblastic tumour.
Case information
URL: https://www.eurorad.org/case/13154
DOI: 10.1594/EURORAD/CASE.13154
ISSN: 1563-4086
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