Inclusion body fibromatosis

Inclusion body fibromatosis is a superficial benign myofibroblastic tumor characterized by eosinophilic intracytoplasmatic inclusions, which is typically seen in infancy and features a propensity for local recurrence.

Terminology

Acceptable alternative terms include infantile digital fibroma or fibromatosis, recurring digital fibroma of childhood, recurring digital fibrous tumor of infancy or infantile dermal fibrosis .

Epidemiology

Inclusion body fibromatosis is a rare condition and accounts for about 2% of fibroblastic tumors in children and for approximately 0.1% of soft tissue tumors .  Almost all cases have been described in children younger than 5 years old. About 30% are detected at birth and the majority of cases within the first year of life. There is no gender predilection .

Clinical presentation

Inclusion body fibromatosis typically manifests as polypoid cutaneous nodules that are usually otherwise asymptomatic .

Pathology

Inclusion body fibromatosis is a proliferative skin-based myofibroblastic tumor with eosinophilic paranuclear cell inclusions .

Etiology

The etiology of inclusion body fibromatosis is unknown .

Location

The classical location of inclusion body fibromatosis involves the dorsal aspects of the distal and middle digital phalanges of hands or feet, with fingers being more frequently involved than toes. The fifth digits are less likely affected. The thumb and great toe are typically spared. Other extradigital locations are rare and include other regions of the extremities, the oral cavity and the breast .

Macroscopic appearance

Macroscopically inclusion body fibromatosis appears as an ill-defined, dome-shaped, cutaneous nodule of white-tannish color and fibrous firm consistency .

Microscopic appearance

The histological spectrum of inclusion body fibromatosis includes the following :

• spindle cells with eosinophilic cytoplasm and bland elongated nuclei
• intracytoplasmic inclusions which can be stained with trichome
• short fascicular, whorling or storiform growth pattern typically perpendicular to epidermis extending into dermis or subcutis
• low mitotic activity
• no cell atypia

Immunohistochemistry

Immunohistochemistry stains can be positive for actin, calponin and occasionally caldesmon .

Radiographic features

Imaging of inclusion body fibromatosis usually reveals a non-specific soft tissue mass. Appearance on cross-sectional imaging has been described as poorly demarcated, heterogenous round to oval,  subcutaneous soft tissue mass with similarities to other superficial fibromatoses.  Osseous involvement has been described in rare events .

Ultrasound

Lesions have been described as isoechoic to hypoechoic .

Radiology report

The radiological report should include a description of the following:

• location and size of nodules
• relation to adjacent bones
• relation to adjacent tendons

Treatment and prognosis

Some lesions might regress spontaneously but local recurrence after excision is also very common. Thus management varies and depends on symptoms. Treatment options include function preserving excision and/or intralesional steroid injections for symptomatic tumors but can also include watchful waiting for asymptomatic lesions .

History and etymology

The entity was initially described by RD Reye et al. in 1965 .

Differential diagnosis

Conditions which can mimic the appearance of inclusion body fibromatosis include :

• palmar and plantar fibromatosis
• lipofibromatosis
• calcifying aponeurotic fibroma

Siehe auch:

• Lipofibromatose