Inflammatory Myofibroblastic Tumour: State of the Art

Abstract

An inflammatory myofibroblastic tumor (IMT) is a neoplasm composed of myofibroblastic and fibroblastic spindle cells accompanied by inflammatory cells, including lymphocytes and eosinophils. It is an ultra-rare tumor, the optimal management of which remains to be defined. Surgery is the treatment of choice for localized tumors. The treatment of advanced disease is not precisely defined. Chemotherapy regimens result in an overall response rate of approximately 50% based on retrospective data. The latest pathophysiological data highlight the role played by tyrosine kinase fusion genes in IMT proliferation. Anaplast lymphoma kinase (ALK) oncogenic activation mechanisms have been characterized in approximately 80% of IMTs. In this context, data regarding targeted therapies are most important. The aims of this article are to review the latest published data on the use of systematic therapy, particularly the use of molecular targeted therapy, and to publish an additional case of an IMT with Ran-binding protein 2 (RANPB2)-ALK fusion showing a long response to a tyrosine kinase inhibitor.

Keywords: ALK; epithelioid inflammatory myofibroblastic sarcoma tyrosine kinase inhibitors; inflammatory myofibroblastic tumour.

Figure 1

Hematoxylin eosin stain of an inflammatory myofibroblastic tumour composed of myofibroblast cells (red arrow) and inflammatory infiltrates (black arrow). Bar = 20 µm.

Figure 2

Hematoxylin and eosin stain of an EIMS composed of epithelioid cells (red arrow) and inflammatory infiltrates (black arrow). Bar = 10 µm.

Figure 3

Immunostaining of an IMT with an antibody against anaplastic lymphoma kinase (ALK) and a peroxidase conjugated secondary antibody. Positive cells were stained with diaminobenzidine (black arrow). Nuclei were counterstained with hematoxylin (red arrow). Bar = 10 µm.

Figure 4

Positron emission tomography (PET) scans showing evolution in time of the abdominal EIMS with large hypermetabolic mesenteric mass, associated with several hypermetabolic intraperitoneal nodules (A) A clear morpho-metabolic regression of the mesenteric mass and secondary intraperitoneal implants previously visualized 3 and 6 months after targeted therapy with alectinib (B,C). (A) Baseline. (B) After 3 months of alectinib. (C) After 6 months of alectinib.