<unk>  (IMT) is a rare neoplasm of the mesodermal cells that form the connective tissues which support virtually all of the organs and tissues of the body. IMT was formerly termed<unk>  pseudotumor. Currently, however,<unk>  pseudotumor designates a large and heterogeneous group of soft tissue<unk> s that includes<unk> , plasma cell granuloma, xanthomatous pseudotumor, solitary mast cell granuloma,<unk>  fibrosarcoma, pseudosarcomatous<unk>  proliferation, myofibroblastoma,<unk>  myofibrohistiocytic proliferation, and other<unk> s that develop from connective tissue cells.<unk>  pseudotumour is a generic term applied to various neoplastic and non-neoplastic tissue lesions which share a common microscopic appearance consisting of spindle cells and a prominent presence of the white blood cells that populate chronic or, less commonly, acute inflamed tissues.<unk>  was initially regarded as a benign<unk>  that most often developed in the lung and less commonly in almost any organ system or tissue. Over time, however, IMT cases occurred in which the<unk>  spread into local tissues, metastasized to distal tissues, recurred after treatment, or consisted of neoplastic cells that had pro-malignant chromosome abnormalities. Consequently, the World Health Organization, 2013, and current literature commonly describe<unk>  as a neoplasm with intermediate malignant potential or a rarely metastasizing neoplasm. In 2020, the World Health Organization reclassified IMT as a specific<unk>  form in the category of intermediate (rarely metastasizing) fibroblastic and<unk> <unk> s. In all events, IMT is a rare<unk>  with a reported incidence in 2009 of 150–200 cases/year in the United States. IMT lesions typically consist of, and are defined by,<unk>  spindle cells, i.e. specialized cells that are longer than wide, have a microscopic appearance that merges the appearances of fibroblasts and smooth muscle cells (see myofibroblast), occur in normal as well as<unk>  tissues, and in normal tissues are commonly designated fibroblasts. However, the lesions in some IMF cases are dominated by sheets of epithelioid cells (which may have rounded shapes) with only a minor component of spindle cells.<unk> s with these characteristics are regarded as a subtype of IMT termed epithelioid<unk><unk>  sarcoma (EIMS). The<unk> s in IMT and EIMS consistently contain pro-inflammatory white blood cells and in most cases<unk>  cells that express highly abnormal oncogenic (cancer-causing) fusion proteins such as those that contain the active portion of anaplastic lymphoma kinase (ALK). It is not clear whether this inflammation, the genetic abnormalities, or both contribute to the development of IMT but drugs blocking the activities of the fusion proteins made by these genetic abnormalities may be useful in treating the disease.
Inflammatory myofibroblastic tumour
Reticulohistiocytoma
Plexiform angiomyxoid myofibroblastic tumor
Giant-cell reticulohistiocytoma
Adenomatoid tumor
Angiomatoid fibrous histiocytoma
Multinucleate cell angiohistiocytoma
Epithelioid sarcoma