CASE 18449 Published on 09.02.2024

Desmoplastic fibroma in the sacrum

Section

Musculoskeletal system

Case Type

Clinical Case

Authors

Theodora Dermitzaki, Georgia Tavladaki, Evangelia Tavladaki, Maria Kokkinaki

Venizeleio General Hospital, Heraklion, Greece

Patient

52 years, female

Categories
Area of Interest Anatomy, Bones ; Imaging Technique CT
Clinical History

A woman, 52 years old, presents in the emergency department complaining of intense low back pain radiating to the right leg, which became more intense in the last 24 hours, preventing her from walking. She also describes milder same symptoms of pain in the last seven months. The patient refers no other remarkable general health problems.

Imaging Findings

CT images from the lumbar spine show right disc herniation at the L5S1 intervertebral space, a finding that explains the symptoms. It is also noticed as incidental finding a lytic lesion on the central and right part of the depicted sacrum.

CT images from the sacroiliac region delineate the location of the lesion, which extends at the central and right parts from I1 to I5 vertebra. On CT, a lytic lesion with soft tissue density is observed replacing normal bone marrow and causing cortical destruction (Figures 1a, 1b and 2).

On MR imaging, the lesion shows low signal intensity on T1 and T2 images in a large area (>75% of lesion) (Figures 3 and 4). In fat sat images, it has a heterogeneous signal consisting of areas with both low and mildly high signal intensity (Figure 5). The lesion has heterogeneous enhancement with the areas of high signal on T2 corresponding to more intense enhancement (Figure 6). No invasion of the spinal nerve roots is observed; instead, retention of intraforaminal fat planes is noticed (Figures 3 and 4).

Discussion

Desmoplastic fibroma is a rare benign primary fibrous bone tumour with an incidence of 0.1% among all primary bone tumours [1]. There are only few reports presenting the diagnosis of desmoplastic fibroma and describing the relative imaging characteristics on CT and MR imaging [2].

It is a slow-growing tumour with potential locally aggressive behaviour affecting more often the metadiaphysis of large long bones,  the mandible and the pelvis [13]. It is seen more often in the third to fourth decade of life and has no sex predilection [1,4].

It may be asymptomatic, but usually it is related to long-standing regional pain and swelling [4,5].

Histologically, it consists mainly of fibrous tissue and is similar to the soft tissue desmoids tumour [1,2,4].

On CT imaging, it is usually osteolytic in appearance, typically with no mineralized matrix [1,4]. Lobulated margins, mild bone expansion and coarse internal trabeculations are indicative of a slow-growing process causing uneven bone destruction [2]. Other usual imaging characteristics are soft tissue density, cortical breaching and pronounced cortical destruction [1,2,4].

On MR imaging, the tumour typically shows a large area of low to intermediate signal on both T1 and T2 images, indicative of its fibrous composition, but heterogeneous signal intensity on T2 fat sat images [1,2,4]. The regions with compact collagen tissue have lower signal intensity on T1 and T2 images and mild or no enhancement. Instead, regions with more cellular tissue present with higher T2 signal intensity and more intense enhancement [2].

Pathologic fracture is responsible for high signal intensity on T2 due to the oedema [2].

Lesions with osteolytic appearance and sites of low signal on T2 have limited differential diagnosis, and desmoplastic fibroma must always be included [1].

The tumour has a high propensity for recurrence after surgical removal; that is why surgical resection with extended margins is the preferred treatment [1,2,4].

In our case, the findings cannot exclude metastatic bone lesion, so the patient is submitted to abdominal and thoracic CT imaging in order to exclude a primary malignancy.

The tumour biopsy reveals desmoplastic fibroma (Figure 7).

The patient is conservatively treated with analgesia and cortisone for acute pain relief related to intervertebral disc herniation.

As surgical resection in the region of the sacrum poses a considerable reconstructive challenge [4], a follow-up with MR is recommended six months later, which shows no differentiation of the size and imaging characteristics of the tumour. The herniated disc part on L5S1 space is reduced in size.

Written informed patient consent for publication has been obtained.

Differential Diagnosis List
Giant cell tumour
Fibrous dysplasia
Desmoplastic fibroma
Lymphoma
Fibrosarcoma
Final Diagnosis
Desmoplastic fibroma
Case information
URL: https://eurorad.org/case/18449
DOI: 10.35100/eurorad/case.18449
ISSN: 1563-4086
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