P38.16 Expression of ROS1 Gene Rearrangement in Pulmonary Inflammatory Myofibroblastic Tumor With Cerebral Metastasis: Case Report

Abstract

Primary pulmonary inflammatory myofibroblastic tumor (IMT) is a rare benign neoplasm; the tumor has been characterized by the application of immunohistochemical techniques, molecular biology and cytogenetics, which are very precious for the diagnosis. The purpose of this case was to determine whether immunohistochemistry for ROS1 could predict ROS1 rearrangement in inflammatory myofibroblastic tumor. A 50-year-old Moroccan man with history of mitral stenosis and mechanical valve replacement; presented to our hospital with a complaint of fatigue; headaches and lower back pain for one month. Contrast-enhanced computed tomography of his chest revealed a heterogenous well-defined mass lesion with central irregular calcification with no mediastinal lymphadenopathy or satellite nodules; this mass involving the left seventh rib and vertebral body and left atrial cavity. CT brain showed four solid enhancing irregular shaped mass lesions with hypodense areas consistent with metastasis CT-guided biopsy of the chest lesion showed fibrosis with dystrophic calcification; and non-specific chronic inflammation. He underwent radical excision of the right frontal lesion, and histopathology was distinctive fascicular growth of spindle cells with with a prominent inflammatory infiltrate, showed weak, diffuse and dot-like cytoplasmic staining with anaplastic lymphoma kinase (ALK)-negative immunohistochemistry and Fluorescence in situ hybridization (FISH) analysis was performed on interphase nuclei on 5 micron thin sections of formalin-fixed paraffin-embedded tissue that was found to be positive for TFG-ROS1 fusion. Because surgical excision was not possible crizotinib therapy (250 mg, bid) was chosen for the existence of ROS1 fusion gene with brain radiotherapy boost to metastasis. Treatment with glucocorticoids (methylprednisolone 1 mg/kg) and radiotherapy (5 days/week for 3 weeks at 3 Gy/fraction, 45 Gy/15 days) was started for cerebral metastasis . After taking crizotinib for 3 months, the strong changes in the size of the pulmonary mass was showed at chest chest computed tomography with decreased infiltration around the adjacent structures. Inflammatory pseudotumour of the lung with brain metastasis is very uncommon; we must continued therapy with crizotinib and long-term follow-up is necessary, for detection of recurrence, metastasis and to understand the natural course, especially in patients with myofibroblastic differentiation ROS1 positive Crizotinib is effective for pulmonary IMT, and should be taken into consideration for the treatment of inoperable pulmonary IMT patients who lack ALK rearrangement.