Anaplastic Lymphoma Kinase Positive Mesenteric Inflammatory Myofibroblastic Tumor in Adult Woman

Inflammatory myofibroblastic tumors (IMTs) are rare mesenchymal neoplasms containing spindle cells and inflammatory components that can be locally aggressive. They have unclear biological behavior and may recur after resection. A 31-year-old woman presented with three months of cough, fatigue, weight loss, abdominal pain, anemia, and elevated inflammatory markers. CT showed a large well-circumscribed enhancing mass in the right colic mesentery. The patient underwent a laparoscopic right colectomy. Pathologic review showed fascicular spindle cells with admixed chronic inflammatory cells. Cells stained diffusely positive for SMA and anaplastic lymphoma kinase (ALK), diagnostic of an IMT. Post-operatively, the patient reported symptom resolution and had normalization of lab values. She remains disease-free at 20 months. IMT is rare in adults, accounting for 0.7%-1.0% of lung tumors. Up to 30% of patients present with elevated inflammatory markers. On imaging, IMTs are soft tissue masses with variable enhancement and fibrosis, often suspected to be malignant neoplasms. Up to 80% of IMTs are driven by altered tyrosine kinase signaling and half of IMTs express ALK, which may be treated in unresectable/recurrent cases using ALK-inhibitors. IMT may recur in 10%-15% of patients. The roles of adjuvant treatments are unclear given the rarity and unpredictable biological behavior. Long-term follow-up with regular radiologic and laboratory surveillance is recommended given possible local recurrence. IMTs are best managed in a multidisciplinary setting given their unpredictable nature. Surgery is the mainstay of IMT treatment with long-term control expected in >80% of adult patients.