Malignant Inflammatory Myofibroblastic Tumor of the Lung with IgG4-Positive Plasma Cells - Abstract
Inflammatory myofibroblastic tumor (IMT) is a rare lesion, described in numerous organ systems. The morphologic diagnosis relies on the presence of a fascicular arrangement of myofibroblasts with admixed lymphoplasmacytic infiltrate and slit-like vessels. We report a case of malignant IMT of the lung with rapid progression and features of IgG4-related disease in a 20 year-old woman. The patient presented with cough and hemoptysis. A chest imaging showed a 6-cm nodular-appearing right upper lobe mass. The lobectomy specimen demonstrated a well-circumscribed mass with a yellow-white fibrous and mucoid cut surface. Microscopic examination revealed storiform fibrosis with foci of atypical spindled cells in the lymphoplasmacytic wellvascularized background. Atypical foci also demonstrated necrosis and abnormal mitotic figures. One out of four regional lymph nodes was positive. The spindle cells showed cytoplasmic positivity with SMA and ALK-1 and no reactivity with AE1/AE3, S-100, CD34, and desmin. FISH study detected rearrangement of the ALK gene at locus p23.2. The lymphoplasmacytic infiltrate showed abundant IgG4 plasma cellswith
a ratio of IgG4 to IgG of 49%, satisfying minimal histopathologic criteria of IgG4- related disease. Two months post resection, the patient returned with multiple pulmonary nodules and mediastinal lymphadenopathy. Her disease was chemotherapy-resistant and soonspread distantly causing death 4 months after diagnosis. Identification of malignant features in inflammatory myofibroblastic tumors should alert physicians of dismal prognosis and guide toward aggressive therapy. Further studies necessary to address the link between malignant IMT infiltrated with predominantly IgG4-secreting plasma cells.