Introduction

Fibromatosis is a rare mesenchymal tumor characterized histologically by proliferation of fibroblasts and myofibroblasts with marked production of intercellular collagen.

They are composed of spindle-shaped myofibroblastic cells, dense deposits of intercellular collagen fibers, variable amounts of extracellular myxoid matrix, and compressed and elongated vessels.

It comprises a broad group of fibrous tissue proliferations of similar histologic appearance that has biologic behavior intermediate between that of benign fibrous lesions and fibrosarcoma.

It is characterized by an infiltrative growth pattern and a tendency toward local recurrence,

which have led some to classify it with malignant soft-tissue neoplasms of which it comprises

fewer than 4%. They indeed vary from benign to intermediate in biological behavior. Intermediately aggressive lesions (locally aggressive) are characterized by infiltrative growth and local recurrence but an inability to metastasize.

Fibromatosis are divided into two major groups: superficial (palmar, plantar) and deep (or desmoids type) forms. (figure 1). These lesions can be categorized by location (superficial or deep) or by the age group predominantly affected. Superficial fibromatoses in adults (palmar and plantar) and children (calcifying aponeurotic fibroma, lipofibromatosis, and inclusion body fibromatosis)

Deep fibromatosis /desmoid type fibromatosis

The term “desmoids tumor” (desmos in Greek means band), first used by Mueller in 1838 to emphasize the bandlike or tendonlike consistency of these lesions, is synonymous with the deep type of fibromatosis. The WHO Committee for Classification of Soft Tissue Tumors in 2002 designated the term desmoid type fibromatosis for this lesion outdating the previous terminology. This group consists of rapidly growing lesions that often reach a large size and have a high tendency to recur after treatment, hence the term “aggressive fibromatosis.” This group principally involves the musculature of the trunk and the extremities.

Deep fibromatosis (desmoid type fibromatosis) are divided into abdominal (abdominal wall fibromatosis), intra or extraabdominal in location.

Desmoid type fibromatosis occurs most frequently in patients in the 2nd to 4th decades of life, with a peak incidence between the ages of 25 to 35 years. Less than 5% of patients are younger than 10 years of age. Women are more commonly affected than men.

Most cases are sporadic, but there is a clear association with familial adenomatous polyposis  and Gardner’s syndrome, suggesting a link with mutations of the APC gene on chromosome 5q22.

All forms of desmoid type fibromatoses are believed to have similar pathogenesis: activation of the β-catenin signaling pathway. Activation can occur either by APC-gene mutations (gene in the long arm of chromosome 5q21-22), usually in connection with familial polyposis syndrome (also referred to as Gardner syndrome), or by somatic β-catenin mutations. In either event, β-catenin is overexpressed, which leads to strongly positive nuclear immunohistochemical staining.

They typically manifests as a deeply seated but poorly circumscribed soft-tissue mass.

Slow insidious growth is common, and lesions are usually painless. Additional symptoms of decreased mobility, reduced joint motion, and neurologic complaints (numbness, tingling, sharp pain, or motor weakness) are less frequent.

While these lesions can occur almost anywhere in the body, they have a predilection for the upper torso including the upper arm (28%), chest wall/paraspinal (17%), and head/neck (10% to 23%). Other less common locations include the thigh (12%), knee (7%), buttock/hip (6%), and forearms (4%). Multicentric disease occurs in 10%-15% of cases.

Extraabdominal fibromatoses have a tendency to grow along fascial planes and can extend a great distance from the predominant mass.

Abdominal wall fibromatosis are distinguished from the other deep musculoaponeurotic fibromatoses because of their location and distinct predilection to develop in women of childbearing age. In fact, 87% of these lesions occur in women, and 95% develop in women who have had at least one child (the lesions usually occur during the first year after childbirth).  Abdominal wall desmoids arise from the musculoaponeurotic structures of the abdominal wall, most frequently the rectus abdominis and internal oblique muscles and their fascial coverings. Abdominal wall desmoid is the most common soft-tissue neoplasm of the abdominal wall. Less often, these lesions originate from the external oblique and the transversalis muscles or fascia. The etiology of these tumors is uncertain. Although the majority of cases are idiopathic, estrogenic hormones, trauma (including surgery - these lesions arise following a surgical procedure in 20% of cases), and genetic abnormalities have also been implicated as potential causative factors. The majority of patients with abdominal wall desmoids have no history of gross injury. Minor undetected trauma such as minute muscle tears may theoretically serve as a contributing factor to development of these lesions in a hormonally or genetically predisposed individual.

Management

Management of deep fibromatosis is challenging because this disease does not respect the usual surgical rules relating to resection and recurrence.

The prefered treatment is usually a wide-local excision.

Adjuvant radiation therapy following surgery has been shown to decrease the local recurrence rate versus surgery alone. In fact various studies have suggested that radiation therapy alone in inoperable cases achieves near equivalent local control compared to surgery.

Additional therapies with reported positive results include radiofrequency ablation and chemotherapy agents.