Locally invasive pulmonary inflammatory myofibroblastic tumors in children.

Two uncommon cases of locally invasive pulmonary inflammatory myofibroblastic tumor are reported. Diagnosis was established by a prior thoracotomy and incisional biopsy. Complete excision was curative and both children remain asymptomatic at last follow up.

INTRODUCTION

Inflammatory myofibroblastic tumor is defined by WHO as a myofibroblastic spindle cell soft tissue tumor with infiltrative plasma cells, lymphocytes, and eosinophils. It has been classified as an intermediate neoplasm in the current WHO histological typing of tumors of soft tissue and bone.[12] Although it has been reported to be the most common benign primary pulmonary tumor in childhood, accounting for more than 50%, these tumors are infrequently encountered in clinical practice. Moreover, these tumors are often a diagnostic dilemma for the surgeon and the pathologist since biopsy reveals only inflammatory cells.[34]

CASE REPORTS

Case 1

An 11-year-old boy presented with complaints of frequent cough and fever since the age of 5 years. The child was initially investigated elsewhere and diagnosed as a case of pulmonary tuberculosis. He had received antitubercular treatment for 1 year. After temporary relief, his symptoms recurred and the sputum showed presence of acid fast bacilli. The child was restarted on antitubercular treatment, which was administered for 2 years. Radiological investigations revealed the presence of a left intrathoracic mass. The child underwent thoracotomy and biopsy elsewhere. The biopsy was suggestive of inflammatory myofibroblastic tumor of the lung. The child was started on prednisolone but remained symptomatic. Subsequently, the child was referred to our institution for definitive treatment. His general condition was good and there was no evidence of respiratory distress. On examination, the movements of the chest wall were diminished on the left side. The left hemithorax was dull on percussion and the air entry was absent. The right side was normal. Chest radiograph showed the presence of a homogenous opacity in the left hemithorax with large areas of calcification in the hilar region. A contrast enhanced CT scan of the chest revealed a large soft tissue mass in the left lung with dense calcification and collapse of the lung. The child underwent thoracotomy; there was a soft tissue mass arising from the left lung and densely adherent to the pericardium, aorta, and thymus. Large mediastinal lymph nodes were present and the left pulmonary vein and artery were encased by the mass. Complete excision of the mass along with the involved pericardium and left pneumonectomy was performed. The child suffered a cardiac arrest during surgery but was revived immediately. Postoperatively, the child required ventilator support for 7 days. The child was subsequently discharged in a stable condition with no neurological deficit. The histopathological examination confirmed the diagnosis of inflammatory myofibroblastic tumor [Figure 1].

Figure 1

Photomicrograph showing an inflammatory cell-rich lesion with small number of benign-looking spindle cells set in a collagenous stroma, the infiltrate consisted of a mixture of mature-looking lymphocytes and plasma cells (H and E, 10×)

Case 2

A 10-year-old boy presented with complaints of breathlessness and fever for the last 3 years along with recurrent cough and expectoration. A history of significant weight loss was present. Bronchoscopy performed elsewhere had revealed inflamed mucosa. The child received anti-tubercular treatment for 4 months. On examination the child had mild respiratory distress with a respiratory rate of 40 per minute. The air entry was decreased on the right side. The chest radiograph revealed an opaque hemithorax on the right side with ipsilateral mediastinal shift [Figure 2]. The contrast enhanced computed tomogram showed a large heterogenous mass in the right hemithorax inferomedial to the hilum along with collapsed right upper lobe [Figure 3]. The child underwent thoracotomy which revealed a firm, hard mass occupying the whole of the right chest and intimately adherent to the diaphragm. An incisional biopsy was performed. The histopathological examination showed features suggestive of inflammatory myofibroblastic tumor. A reoperation was performed two months later for excision of the mass. The mass was densely adherent to the diaphragm and encasing the right pulmonary hilum. Excision of the tumor along with right pneumonectomy and partial excision and repair of right hemidiaphragm was performed. The postoperative period was uneventful and the child was discharged in a stable condition. The histopathological examination showed bronchiectatic changes in the lung and the tumor showed features of inflammatory myofibroblastic tumor of the lung.

Figure 2

Chest radiograph showing a large soft tissue tumor on the right side with ipsilateral mediastinal shift and collapse of the lung

Figure 3

CT scan showing a heterogenous mass in the right hemithorax

DISCUSSION

The first description of this tumor was given by Brunn in 1939 who described “two interesting benign lung tumors of contradictory histopathology”.[5] In 1955, this tumor was given the name plasma cell granuloma by Lane et al. since plasma cells were predominant in the tumor.[6] Thereafter many different terms[7] were used to describe this tumor, the most common being inflammatory pseudotumor. The other synonyms used were post inflammatory tumor, xanthofibroma, xanthogranuloma, fibrohistiocytoma, plasma cell granuloma, pseudosarcomatous myofibroblastic tumor, and invasive fibrous tumor of the tracheobronchial tree. Inflammatory myofibroblastic tumor is now considered a more appropriate term as it takes into consideration the ultrastructural and immunohistochemical properties of this tumor.[8]

Inflammatory myofibroblastic tumors can affect any organ of the body but the pulmonary, gastrointestinal and genitourinary systems are commonly affected. The etiology of this condition is unknown but it is considered as a reactive lesion to tissue injury which is supported by the observation that antecedent respiratory infection is present in one third of the patients. Also HHV-8 and EBV DNA sequences have been documented in some tumors indicating that viral infection may have some role in pathogenesis of this tumor.[8] Nearly, 70% patients will be symptomatic with complains of fever, cough, dyspnea, and rarely hemoptysis. CT scans usually show a well-circumscribed, solitary, peripheral pulmonary nodule or mass with a variable and nonspecific appearance. Intratumoral calcification has been identified in about 15% of cases. Most inflammatory myofibroblastic tumors are well-circumscribed, nonencapsulated parenchymal masses, with less than 5% invading the mediastinum and chest wall.[910] Also the preoperative diagnosis is usually not possible as the tissue or cells available by percutaneous biopsy or aspiration cytology is small and reveals only inflammatory cells thereby making difficult to definitively diagnose this tumor.

The treatment of thoracic inflammatory myofibroblastic tumors is surgical excision of the tumor along with pulmonary conservation if possible. Recurrence rates are 1.5% in tumors confined to the lung and 46% in locally invasive tumors with extension beyond the lung.[11] Recurrence is rare in cases with complete resection of the tumor. Radiation, steroids and non steroidal anti inflammatory drugs have been used to treat inflammatory myofibroblastic tumors with variable and inconsistent results. Hence, surgical excision still remains the treatment of choice.