Patients not affected by FAP, in general, Desmoid Fibromatosis (or Desmoid Tumor) manifests itself as a mass of variable dimensions of hard-wood consistency, that can be appreciated only if it arises in superficial areas.

Due to its rarity, often doctors not specialized in this disease can be wrong with the first diagnosis, confusing it with a low-grade lipoma or liposarcoma and surgically removing it before a biopsy. Surgery can be burdened by a high risk of recurrence, regardless of the adequacy of the margins.

For this reason, before taking any decision, it’s very important to refer to a specialist in surgery/oncology of sarcomas, relying on one of the reference centers in Italy.

The specialist Doctor will proceed with the following tests:

A CLINICAL EXAMINATION of the tumor to evaluate its consistency: the desmoid appears as a hard swelling, on which the superficial sides flow and more fixed on the deep ones. It may not be associated with pain especially in the early period. Sometimes it can involves compression of nearby nerve structures and/or limitations in movement, causing pain on palpation, twinges and electric shocks, referred as “internal needle-and-pin pricking” pains (paraesthesia). Its growth is slow even if it can have periods of greater development and generally it becomes manifest in an average time of 3 years.

A RADIOLOGICAL EXAM that can be MRI or CT scan. More in detail:

Nuclear magnetic resonance (NMR), is the best choice for DFs except for intra-abdominal DFs in which CT is preferred at least for early diagnostic period.

It reveals the presence of an expanding infiltrating mass, with poorly defined margins and with diffuse uptake of the contrast medium (ENHANCEMENT). The diagnostic key in desmoid MRI lies in the identifiable T2 hypointense bands

An association was shown between the growth and the high intensity of the T2 signal.

MRI uses a magnet to create an image of the inside of the body. It’s the most frequently used examination in the suspicion case of DF because it doesn’t expose the patient to radiation so MRI is the best exam also to perform periodic checks, which will initially be every 3 months, afterwards every 6 months and then once a year (if the tumor is stable).

During early years, checks include the use of contrast medium for MRI, which can be avoided lately if not explicitly requested by the Doctor.

MRI’s parameters to evaluate the response to treatment or spontaneous regression are:

• Decrease in tumor size
• Increased hypointensity in T2
• Reduction of contrast media uptake

CT – computed tomography (CT)  – uses ionizing radiation to reconstruct 2D images of the section studied. It is mainly used for INTRADDOMINAL Desmoid Tumors because CT images are less influenced by movement associated with intestinal peristalsis and diaphragmatic excursion during breathing.

Furthermore, compared to MRI, desmoids studied by CT can be more easily distinguished from adjacent mesenteric fat or fluid-filled loops.

CT exam has more advantages compared to MRI:

• It’s more repeatable and faster
• Some patients may suffer from claustrophobia and cannot tolerate the narrow space of the MRI for long and the duration of the exam depends on the area of the body to be examined but generally lasts at least 30 minutes. The CT scan instead is associated with much shorter image acquisition times, as few minutes.
• Some metal devices, such as pacemakers and some implants, are incompatible with magnetic fields used for MRI. Patients with these devices do CT rather than magnetic resonance imaging.

COLONSCOPY: Colonoscopy is an endoscopic examination that involves the use of a flexible tube to observe the mucous membrane of the colon. It is indicated only in patients with suspected hereditary syndromes, such as FAP.

A BIOPSY is necessary to confirm the diagnostic suspicion: THE MICROSCOPIC DIAGNOSIS SHOULD BE CONFIRMED BY A SPECIALIZED PATHOLOGIST. It requires a piece of tissue (biopsy) that the Pathologist observes with the microscope. The tissue fragment can be taken through a biopsy or from a surgically removed tumor. The histological diagnosis of DF should be confirmed by a pathologist experienced in soft tissue tumors. 85-90% of DFs are characterized by specific genetic mutations that can be highlighted by a test called “mutational analysis”. Finding these mutations helps identify DF with more certainty.

Biopsy can be done:

• Through needle biopsygo-biopsia: this is the best choice, it involves the collection of small tumor samples of between 1 and 10mm in size and it’s done UNDER LOCAL ANESTHESIA.
• Incisional biopsy: it’s a surgical biopsy to take a part of the tumor.
• The excisional biopsy which consists in removing the entire suspicious area is not indicated for the diagnosis of DF.
• Histological examination: on a macroscopic level, proliferation frustules with spindle cells of fibro-myofibroblastic will be highlighted, without evident cytological atypia and separated by abundant and dense collagen. Irrelevant mitotic index and absent necrosis.

Macroscopically, DF appears as a gray-brownish neoformation, with a collated appearance when cut, with a tense-elastic consistency, translucent appearance and in continuity with the muscle tissue; this characteristic is also evident from the microscopic point of view with infiltrative attitudes towards the striated muscle tissue. This characteristic lack of boundaries with healthy tissue justifies the high local recurrence and the great difficulty to define the limits of resection for a surgery.

• The IMMUNOHISTOCHEMICAL EXAMINATION cwill follow which shows the expression of muscle cell markers (actin, desmin, vimentin) and the absence of CD34.

• MUTATIONAL ANALYSIS: urthermore, the diagnosis can be confirmed by screening for CTNNB1 mutations, that is the mutation of the β-catenin gene, which will exclude the APC mutation and Gardner’s Syndrome.