Mesenteric inflammatory myofibroblastic tumors.

Inflammatory myofibroblastic tumors (IMTs), also known as inflammatory pseudotumors and inflammatory fibrosarcomas, are uncommon mesenchymal tumors composed of myofibroblastic spindle cells admixed with lymphocytes, plasma cells and eosinophils. Once thought to be reactive, these lesions are now considered to be neoplastic. These tumors can occur throughout the body, most commonly in the lung, mesentery and omentum. Patients commonly present with painless abdominal mass or with intestinal obstruction. IMTs may be multicentric, have a high local recurrence rate and may metastasize in rare cases. The lesions show wide variability in their histologic features and cellularity, and marked inflammatory infiltration, predominantly of plasmatocytes and lymphocytes, and occasionally neutrophils and eosinophils. Anaplastic lymphoma kinase (ALK) rearrangements and/or ALK1 and p80 immunoreactivity are reported in 33-67% of the tumors. Owing to the rarity of these lesions, there are no specific imaging findings that distinguish IMTs from other mesenteric masses. Complete surgical resection is the treatment of choice. Local recurrence rates are high, and re-excision is the preferred therapy for local recurrences. ALK-positive tumors show good response to ALK inhibitors. Current knowledge and comprehensive review of the available literature on IMTs is herein presented.