Calcifying fibrous tumor

Calcifying fibrous tumors, previously known as calcifying fibrous pseudotumors, are rare, benign fibroblastic tumors of the soft tissues.

Epidemiology

It can occur at all ages and there is no strong gender predilection ¹. Fewer than 200 cases have been reported in the English literature ¹.

Clinical presentation

Most cases are asymptomatic, so the tumor is found incidentally on imaging ¹. When symptoms are present, they are nonspecific and include palpable painless mass or localized pain ¹.

Pathology

Location

Calcifying fibrous tumors can occur throughout the body's subcutaneous or deep soft tissues, with a few sites being more commonly reported ¹:

• stomach (18%) ⁶
• pleura (10%)
• small intestine (9%) ⁵
• peritoneum (7%) ³
• neck (6%) ⁸
• mesentery (5%)

Many other sites have been described, such asincluding calcifying fibrous tumor of the lung, liver ², and between muscles ⁸. Association with bone is unusual but a case involving the clivus has been reported ⁴.

Classification

The entity is included in the WHO classification of tumors of soft tissue under the fibroblastic/myofibroblastic tumors category.

Macroscopic appearance

It is a circumscribed, nonencapsulated mass and occasionally infiltrates surrounding tissues ¹.

Microscopic appearance

The lesion is composed predominantly of hyalinized stroma with interspersed psammomatous and dystrophic calcifications, fibroblastic spindle cells, and mononuclear/lymphoplasmacytic inflammatory infiltrate ^1,3.

Radiographic features

The appearance depends on the site but in general reflect the histology ^1-7.

Plain radiograph

A mass is present with calcifications.

CT

Partially calcified mass is demonstrated with some contrast enhancement, which progresses on delayed images.

Ultrasound

The mass is hypoechoic with acoustic shadowing and foci of hyperechoic calcifications.

MRI

The mass has the following signal characteristics suggesting fibrosis/collagenous content:

• T1: slightly low signal intensity
• T2: low signal intensity
• T1 C+: relatively hypovascular but with slow progressive enhancement

Treatment and prognosis

Surgical excision is curative. The condition is benign, without reports of mortality; recurrence is rare ¹.

Differential diagnosis

The differential diagnosis is broad and depends on location but includes mesenchymal tumors such as ¹:

• inflammatory myofibroblastic tumor, 
• solitary fibrous tumor, and
• gastrointestinal stromal tumor¹.