Inflammatory myofibroblastic tumor (IMT) is a rare tumor originating from mesenchymal cells, the building blocks of connective tissues. While considered an intermediate-grade tumor, it can be locally aggressive but rarely spreads to distant sites. IMT often presents a diagnostic challenge because its varied clinical and radiological appearances can mimic more aggressive malignancies. An estimated 150-200 people are diagnosed with IMT annually in the United States.
Understanding Inflammatory Myofibroblastic Tumor
IMT is characterized by myofibroblastic cells, a blend of fibroblasts and smooth muscle cells, and inflammatory cells, predominantly plasma cells, lymphocytes, and eosinophils, which contribute to its “inflamed” appearance.
These tumors can develop in almost any part of the body, but they are most frequently found in the lungs and abdominal areas, including the mesentery and retroperitoneum. While IMTs can affect individuals of any age, they are more commonly observed in children and young adults.
The behavior of IMT can be unpredictable. The tumor may invade nearby tissues, potentially obstructing organs like the lung or stomach. Although rare, IMT can recur after treatment, and in less than 5% of cases, it may spread to distant organs.
Diagnosing Inflammatory Myofibroblastic Tumor
Initial symptoms of IMT are often vague and non-specific, making early detection difficult. Patients may experience fever, night sweats, weight loss, or general discomfort, depending on the tumor’s location and size. Pain at the tumor site is also a common symptom.
Imaging studies like X-rays, CT scans, and MRI scans are the first step in identifying suspected IMT and determining its size and location. However, these scans alone cannot definitively diagnose IMT because its appearance can resemble other types of tumors.
A definitive diagnosis relies on a biopsy, where a tissue sample is taken from the tumor. This sample undergoes a histopathological examination under a microscope, revealing myofibroblastic spindle cells intermixed with inflammatory cells.
Immunohistochemistry is a laboratory technique that aids diagnosis by identifying specific proteins within tumor cells. About 50-70% of IMT cases show rearrangements of the anaplastic lymphoma kinase (ALK) gene, leading to ALK protein expression. Detecting ALK gene rearrangements through techniques like fluorescence in situ hybridization (FISH) or next-generation sequencing (NGS) is a significant marker for confirming IMT and distinguishing it from other conditions.
Treatment Approaches for Inflammatory Myofibroblastic Tumor
Treatment strategies for inflammatory myofibroblastic tumor are tailored to the tumor’s characteristics, including size, location, and symptoms. The primary approach for localized tumors is surgical removal. Complete surgical resection with clear margins often leads to a favorable prognosis and can be curative.
For cases where surgery is not feasible due to location, extensive nature, or recurrence, medical therapies are considered. Corticosteroids and non-steroidal anti-inflammatory drugs (NSAIDs) may be used to manage inflammation and reduce tumor size.
When the tumor exhibits ALK gene rearrangements, targeted therapies, ALK inhibitors, have shown promising results. Crizotinib, a first-generation ALK tyrosine kinase inhibitor, received approval in 2020 for treating unresectable ALK-positive IMT. Other ALK inhibitors, such as ceritinib, alectinib, brigatinib, and lorlatinib, have also shown efficacy in ALK-positive IMT. Chemotherapy, though less common, may be considered for aggressive or recurrent tumors, with regimens including anthracycline-based drugs or methotrexate plus vinblastine/vinorelbine. A multidisciplinary team, including surgeons, oncologists, and pathologists, is often involved to develop the most appropriate treatment plan.
Living with Inflammatory Myofibroblastic Tumor and Outlook
Consistent follow-up is important after IMT treatment due to the possibility of recurrence. IMT can reappear, sometimes years later, making ongoing monitoring with imaging and laboratory tests necessary.
The overall outlook for individuals with IMT is generally positive, especially when the tumor has been completely removed through surgery. However, managing tumors that cannot be fully resected or that recur can present more complex challenges.
Although rare, there is a possibility of malignant transformation, where the tumor becomes more aggressive. Ongoing research continues to improve the understanding of IMT’s biological behavior and to develop new therapeutic options. Patient support networks and medical advancements improve long-term outcomes for those living with this condition.