Sinonasal inflammatory myofibroblastic pseudotumor (plasma cell granuloma).

Inflammatory myofibroblastic pseudotumor (plasma cell granuloma) is a soft tissue lesion consisting of myofibroblasts, mature lymphocytes, histiocytes, plasma cells, eosinophils, and extracellular collagen. Various sites in the body may harbor these lesions. Lungs, omentum, intestines, mesentery, and urinary system are the most susceptible areas. It is usually seen in children and young adults. The lesion is rarely detected in the head and neck region. The orbit and the upper respiratory system are the most common localizations in the head and neck region. Sinonasal tract is a rare site of involvement. The differential diagnosis includes squamous cell carcinoma (spindle cell variant), inflammatory fibrosarcoma, leiomyosarcoma, schwannoma, and nonspecific inflammation. Our patient who had a sinonasal mass showed a benign tumor consisting of spindle tumor cells and inflammatory cells histopathologically. This case was presented due to its rare existence to this site.