IMTs

Inflammatory myofibroblastic tumor (IMT) is a rare mesenchymal neoplasm characterized by proliferating myofibroblastic spindle cells accompanied by an inflammatory infiltrate. It is classified by the World Health Organization as a tumor of intermediate biological potential, meaning it has a tendency for local recurrence and, less commonly, metastasis, but is not considered highly malignant.

IMTs most commonly affect children and young adults, though they can occur at any age. They arise throughout the body, with the lungs and upper abdomen being frequent sites; other common locations include the retroperitoneum, pelvis, omentum, liver, and mediastinum.

Histologically, IMTs show spindle-shaped myofibroblastic cells in a myxoid to collagenous stroma with an inflammatory infiltrate dominated by plasma cells and lymphocytes. About half of cases harbor rearrangements of the anaplastic lymphoma kinase (ALK) gene, leading to ALK protein expression detectable by immunohistochemistry. Other genetic alterations, such as ROS1 and PDGFRβ rearrangements, have been described in some tumors.

Clinical presentation depends on location and size and may include a palpable mass, pain, fever, or weight loss. Radiologic findings are variable and non-specific; diagnosis relies on biopsy with histology and immunohistochemistry.

Management typically starts with complete surgical excision when feasible. Recurrence occurs in a subset of patients, especially after incomplete resections. Corticosteroids, nonsteroidal anti-inflammatory drugs, and radiotherapy have been used in selected cases. For ALK-rearranged or unresectable tumors, ALK inhibitors such as crizotinib have shown activity.

Prognosis is generally favorable after complete excision, but long-term follow-up is recommended due to the risk of recurrence.