Benign but recurrent and which can be locally very invasive, desmoid tumors, or aggressive fibromatosis, are rare tumors that develop from tissues and muscle envelopes (aponeuroses). Unpredictable development, they can be the source of pain and significant functional discomfort. The management is complex and requires the intervention of a multidisciplinary expert team.

Definition

Desmoid tumors or aggressive fibromatosis are rare tumors made up of fibrous cells that resemble normal cells in fibrous tissue called fibroblasts. Belonging to the category of connective tumors (“soft” tissue tumors), they develop from muscles or muscle envelopes (aponeuroses).

These are benign tumors – they are not the cause of metastases – but of very unpredictable evolution, which often prove to be very invasive locally and highly recurrent even if some evolve little or are even likely to regress spontaneously.

They can arise anywhere in the body. The superficial forms preferentially reach the limbs and the abdominal wall, but the neck and the head (in young children) or the thorax can also be the seat. There are also deep forms of desmoid tumors (intra-abdominal localization).

Causes

The origin of desmoid tumors remains poorly understood, but is thought to be multifactorial, with the involvement of hormonal and genetic factors.

Accidental or surgical trauma (scars) seem to be one of the causes of their appearance, as well as childbirth (at the level of the abdominal wall).

Diagnostic

Imaging examinations show the presence of an infiltrating mass which grows over time. The diagnosis is mainly based on CT (computed tomography or CT) for intra-abdominal tumors or MRI (Magnetic Resonance Imaging) for other tumors.

A biopsy is needed to confirm the diagnosis. To rule out the risk of confusion, histological analysis (examination under a microscope) must be carried out by a doctor specializing in pathology with experience in these tumors.

Genetic tests can be carried out in addition to detect possible mutations.

The people concerned

Desmoid tumors mostly affect young adults, peaking around the age of 30. The disease mainly affects women. Children are also to be affected, especially in the early teens. 

It is a rare tumor (0,03% of all tumors), appearing with a frequency estimated annually at only 2 to 4 new cases per million inhabitants.

Risk factors

In families affected by familial adenomatous polyposis, a rare inherited disease characterized by the existence of colon multiples, the risk of developing a desmoid tumor is higher than in the general population and is estimated to be around 10 to 15%. It is associated with mutations in a gene called APC (tumor suppressor gene), involved in this disease.

However, the vast majority of cases of aggressive fibromatosis appear sporadically (without hereditary background). In about 85% of these non-transmissible cases, tumor transformation of cells is then associated with accidental mutations of the gene CTNNB1, causing the modification of a protein which is involved in the control of tumor proliferation called beta-catenin.

Swelling

Desmoid tumors create swelling that is detected on palpation as firm, mobile, sometimes very large “balls” that often adhere to nearby organic structures.

pain

The tumor is painless on its own but can cause severe muscle, abdominal or nerve pain depending on its location.

Functional genes

The compression exerted on neighboring tissues can cause various functional abnormalities. Compression of the nerves can, for example, be the cause of a reduction in the mobility of a limb. The deep forms affect the blood vessels, the intestine or the urinary system, etc.

Loss of function of the organ involved is possible.

Some desmoid tumors also have a fever.

There is no standardized therapeutic strategy and it is decided on a case-by-case basis by an expert multidisciplinary team.

Stable desmoid tumors can be painful and require pain treatment. 

Active surveillance

Formerly practiced, surgery is now abandoned in favor of a conservative approach which consists in closely monitoring the evolution of the tumor before imposing a sometimes heavy treatment which would not be necessary.

Even when the tumor is stable, pain management may be necessary.

surgery

Complete surgical removal of the desmoid tumor is preferred when it is possible and the extension of the tumor allows it without causing major functional loss (eg amputation of a limb).

Radiotherapy

It can be used to try to make the desmoid tumor regress or stabilize it, in the event of progression, of relapse or to decrease the risk of recurrence after surgery. Due to its harmful effects on growing individuals and is used very little in children. 

Drug treatments

Different molecules have a more or less well established efficiency and are used alone or in combination. In particular, tamoxifen, an active anti-estrogen drug is used when the tumor is sensitive to this female hormone, to non-steroidal anti-inflammatory drugs, to different types of chemotherapy (methotrexate, vinblastine / vinorelbine, pegylated liposomal doxorubicin) or to molecular therapeutics targeted drugs that block tumor growth (imatinib, sorafenib), given as tablets.

Other treatments

• Cryotherapy is applied under general anesthesia to destroy tumors by freezing them in

  – 80 ° C.

• Isolated limb infusion involves infusing high-dose chemotherapy into the affected limb only.

These procedures are only offered in a few expert centers in France.

Evolution

In about 70% of cases, local recurrence of the tumor is observed. The vital prognosis is not engaged, except in the case of complications of the surgery, in particular for abdominal tumors.