Diagnosis & Discussion

Diagnosis

Desmoplastic fibroma of bone.

Discussion

Desmoplastic fibroma (DF) is a rare benign but locally aggressive bone tumor with an incidence of about 0.1-0.3% of all primary bone tumors. It most commonly occurs during the second or third decade of life with most cases involving the femur, tibia, mandible, and pelvis. Radiographically, these lesions are radiolucent with a honeycomb or trabeculated, appearance and well-defined borders. However, sometimes there is erosion of cortex with extension into soft tissue.

DF was initially described in 1958 by Jaffe because of its histological similarity to a desmoid tumor and DF of bone is thought to represent an intraosseous desmoid-type fibromatosis. Microscopically, DF has variable cellularity with abundant collagen matrix, admixed small-caliber blood vessels, and extravasated red blood cells. The lesion consists of spindle cells (fibroblasts/myofibroblasts) arranged in sweeping fascicles with minimal to absent cytologic atypia. The immunophenotype of this entity is nonspecific but a small fraction can show nuclear staining for β-catenin and mutations in CTNNB1 or APC gene. The histologic differential diagnoses of DF include low-grade fibrosarcoma of the bone (more cellular with herringbone pattern and cytologic atypia), fibrous dysplasia (curvilinear trabeculae of woven bone, storiform pattern), well-differentiated osteosarcoma (bony matrix, MDM2 and CDK4+), and bony invasion by a soft tissue desmoid-type fibromatosis (correlation with radiographic and clinical findings).  

In summary, DF is a rare primary bone tumor that is benign but behaves in a locally aggressive fashion. DF of bone is thought to represent the bony counterpart of soft tissue desmoid-type fibromatosis. DF tends to occur in the long bones, mandible, and pelvis. Histologically, DF is composed of bland spindle cells in broad sweeping fascicles with minimal to no cytologic atypia. The immunoprofile is non-specific and only a minority of cases demonstrate nuclear β-catenin staining. Complete excision is the treatment of choice, either en bloc resection or aggressive curettage.

References

1. N. Said-Al-Naief, R. Fernandes, P. Louis, W. Bell, and G. P. Siegal, “Desmoplastic fibroma of the jaw: a case report and review of literature,” Oral Surg Oral Med Oral Pathol Oral Radiol Endod, vol. 101, no. 1, pp. 82–94, 2006.

2. S. E. Smith and M. J. Kransdorf, “Primary musculoskeletal tumors of fibrous origin,” Seminars in Musculoskeletal Radiology, vol. 4, no. 1, pp. 73–88, 2000.

3. Jaffe H.L. Tumours and tumorous conditions of the bones and joints. In: Lea, Febiger, editors. Lea and Febiger; Philadelphia: 1958. pp. 298–303

4. G. Petur Nielsen,Andrew E. Rosenberg. Pleomorphic Liposarcoma. https://app.expertpath.com/document/desmoplastic-fibroma/67efb6e5-36c6-49f7-9a4a-67a5966936bd?searchTerm=Desmoplastic%20Fibroma. Accessed December 1, 2021.

5. Coindre J-M. Pedeutour F. In Fletcher CDM, Bridge JA, Hogendoorn P, Mertens F. (2013). WHO Classification of Tumours of Soft Tissue and Bone. Fourth Edition. Lyon, France: IARC.

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