[Biology and signaling pathways involved in the oncogenesis of desmoid tumors]. / Biologie et voies de signalisations impliquées dans l'oncogenèse des tumeurs desmoïdes.

Desmoid tumors (TDs) are derived from mesenchymal stem cells and their pathogenesis is strongly linked to the Wingless/Wnt cascade where the deregulation of ß-catenin plays a major role. A mutation of the CTNNB1 encoding ß-catenin is found in the majority of sporadic TD cases and constitutional mutations of APC have been described in heritable forms in patients with familial adenomatous polyposis (FAP). Estrogens could also play a role in pathogenesis and this is the basis for the use of hormone therapy. Other signaling pathways have been involved in the development of TDs such as Notch, Hedgehog, JAK/STAT, PI3 Kinase/AKT and mTOR. Metalloproteases are expressed in TDs and play a role in invasiveness. TGF-ß, as a growth factor, stimulates the transcriptional activity of ß-catenin. Future studies will need to focus on better describing and understanding the immune environment of TDs. One of the major difficulties for the experimental study of TDs is the virtual absence of a preclinical model, either in vitro or in vivo. This is partly why the interactions between the different signaling pathways presented here and their consequences for the development of TDs are still poorly understood.

[Desmoid tumors: Are there still any surgical indications?] / Tumeurs desmoïdes : reste-t-il des indications chirurgicales ?

After an adapted imaging, the diagnosis of a desmoid tumor (DT) is provided by a percutaneous microbiopsy, with a molecular analysis for beta-catenin or APC gene mutation. The therapeutic strategy must be decided in a specialized multidisciplinary tumor board (MTB). Surgery is no longer the first-line treatment for a DT. Except within a surgical complication, active surveillance is offered to the majority of patients, since more than half stabilize or regress after an initial progression, whether the location is peripheral or intra-abdominal. If the localization and/or volume are likely to be functional or life-threatening, medical induction therapy is discussed in MTB, before a local treatment whose potential sequelae would be definitive. Incomplete unplanned resection, recurrence, pregnancy or desmoids occurring in a polyposis context are no longer routine surgical indications. In an emergency setting (occlusion, peritonitis), it is discussed to treat only the mechanical complication and leave the DT in place, if its resection would lead to too much digestive resection, especially in patients who have already undergone colectomy for polyposis. The best indications for surgery are patients who have parietal locations with significant and documented progression, because surgery can be easily completed at the cost of an acceptable morbidity. In localizations where surgery would cause sequelae, medical treatment or other regional loco treatments are discussed in MTB.