Introduction
The Inflammatory myofibroblastic tumor (IMT) is a rare tumor that affects the lungs. It commonly affects children and young individuals. It is also called an inflammatory pseudotumor. Inflammatory pseudotumor denotes various neoplastic and non-neoplastic tumors with a common microscopic appearance consisting of spindle cells and white blood cells. The inflammatory myofibroblastic tumor is a rare, low-grade malignant tumor.
What Is Inflammatory Myofibroblastic Tumor of the Lung?
The inflammatory myofibroblastic tumor is a rare type of tumor that affects the mesodermal cells. The mesodermal cells form the connective tissues that support the organs and tissues of the body. It was initially called inflammatory pseudotumor. However, it is a large and heterogenous group of soft tissue tumors, according to the current scenario. This includes inflammatory myofibroblastic tumors, plasma cell granuloma, inflammatory myofibrohistiocytic proliferation, inflammatory fibrosarcoma, xanthomatous pseudotumors, solitary mast cell granuloma, pseudosarcomatous myofibroblastic proliferation, myofibroblastoma, and other tumors that develop from the connective tissue cells.
The inflammatory myofibroblastic tumor was initially considered a benign tumor that commonly developed in the lungs and less commonly in almost any organ system or tissue. However, it was later identified as a tumor with neoplastic cells with pro-malignant chromosomal abnormalities. It showed metastasis into local tissues and distal tissues and also recurrence after treatment. The world health organization (WHO) described the inflammatory myofibroblastic tumor as a neoplasm with intermediate malignant potential or a rarely metastasizing neoplasm in the year 2013. It was reclassified as a specific tumor form in the category of intermediate fibroblastic and myofibroblastic tumors.
How Does Inflammatory Myofibroblastic Tumor Occur?
The inflammatory myofibroblastic tumor of the lungs is not known to run in families. Inflammatory myofibroblastic tumors are formed due to chromosomal abnormalities. It is due to the expression of an abnormal ALK (anaplastic lymphoma kinase) protein in the ALK gene. The ALK gene translocates and stimulates cell growth, proliferation, survival, and other tumor-promoting functions.
The tumor consists of myofibroblastic spindle cells. These are specialized cells that are longer and have a microscopic appearance that merges the appearance of fibroblasts and smooth muscle cells. It occurs in normal and tumor tissues. The lesion also contains epithelioid cells, in some cases with a minor component of spindle cells. This is a subtype of inflammatory myofibroblastic tumor, which is called epithelioid inflammatory myofibroblastic sarcoma (EIMS). Both tumors contain pro-inflammatory white blood cells that, in most cases, express cancer-causing fusion proteins. It is unknown whether this inflammation, genetic abnormalities, or both cause the inflammatory myofibroblastic tumor.
What Are the Organs Affected in Inflammatory Myofibroblastic Tumor?
The inflammatory myofibroblastic tumor affects the lungs predominantly. It is typically a parenchymal tumor and rarely intrabronchial. It involves the pleura of the lungs. It also affects the greater omentum, or less commonly, the heart, liver, spleen, pancreas, colon, small intestine, spermatic cord, prostate, uterus, eye orbit, peripheral or central nervous system nerves, brain meninges, spinal cord, or other sites. This tumor is also reported in other sites like the lower limb, hip, upper limb, shoulder, head, face, neck, abdomen, thoracic wall, urinary bladder, anal canal, and sites adjacent to the meninges like nasopharynx, middle ear, paranasal sinuses, infratemporal fossa, and pterygopalatine fossa. It usually presents as a localized tumor, but it may undergo distal metastasis.
What Are the Symptoms Associated With Inflammatory Myofibroblastic Tumor?
The symptoms associated with inflammatory myofibroblastic tumors are pain, swelling, formation of a mass, and organ dysfunction. Symptoms of lung involvement are cough, chest pain, shortness of breath, and hemoptysis. Symptoms like fever, chills, night sweats, and weight loss are also present due to systemic inflammation. Rare cases of this tumor may develop in individuals with organizing pneumonia; infection by Mycobacterium avium intracellulare (causes pneumonia) or Corynebacterium jejuni (causes gastroenteritis); Lysinibacillus sphaericus (causes lung infections and sepsis); Epstein-Barr virus-associated lymphoproliferative malignant diseases; and Escherichia coli related occlusive phlebitis of intrahepatic veins; or previous abdominal surgery; trauma; ventriculoperitoneal shunt in the brain; radiation therapy; and corticosteroid usage. However, the relationship between these diseases with the inflammatory fibroblastic tumor of the lungs is unknown.
How Is Inflammatory Myofibroblastic Tumor Diagnosed?
The diagnosis is based on radiographic imaging and histopathological examination of the tumor.
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Histopathological Examination - It reveals the presence of myofibroblastic spindle cell sheets in a matrix background containing gelatinous mucopolysaccharides and non-sulfated glycosaminoglycans. The matrix also contains inflammatory cells like plasma cells and lymphocytes mixed with eosinophils and neutrophils. The epithelioid inflammatory myofibroblastic sarcoma subtype shows the presence of sheets of epithelioid to round cells within the matrix. It is present in a collagenous or mixed myxoid-collagenous matrix with less than five percent of spindle cells and an inflammatory cell infiltrate with predominantly neutrophils, or less commonly lymphocytes, plasma cells, or eosinophils.
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Radiographic Imaging - Radiographic imaging confirms the presence of a single, lobulated mass in the lower lobe. The tumor presents as a well-circumscribed, non-encapsulated, solitary tumor that is firm and white to gray in color. It may show hemorrhage, necrosis, and calcification.
How Is Inflammatory Myofibroblastic Tumor of the Lungs Treated?
The treatment of inflammatory myofibroblastic tumors depends on the location of the tumor, the protein it makes, and the presence of metastasis.
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Surgical Resection - Surgical resection is the mainstay treatment for inflammatory myofibroblastic tumors of the lung.It has a low recurrence rate. Localized tumors can be treated with total resection. Recurrences of localized treatment may also be treated with total resection. Tumors that are not resectable or those that occur in inaccessible sites require aggressive treatment.
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Chemotherapy is given for fast-growing and recurrent tumors. Targeted therapy with ALK inhibitors is also approached to treat this tumor.
What to Expect With Myofibroblastic Tumor of the Lungs?
The prognosis depends on the location of the tumor, whether the tumor has spread to other parts, and the amount of tumor removed during the surgery. Individuals with complete resection of the tumor perform well and have a good survival rate.
Conclusion
The Inflammatory myofibroblastic tumor is a rare tumor that affects the mesodermal cells that form the connective tissue for various organs in the body. Lungs are predominantly affected by this tumor. Lung involvement can be invasive or non-invasive. It can be treated with surgical resection and other therapeutic options.
