Clinicopathological and genetic study of a rare occurrence: Malignant transformation of fibrous dysplasia of the jaws

DNA Mutational and Copy Number Variation Profiling of Primary Craniofacial Osteosarcomas by Next-Generation Sequencing

BACKGROUND

Craniofacial osteosarcomas (CFOS) are uncommon malignant neoplasms of the head and neck with different clinical presentation, biological behavior and prognosis from conventional osteosarcomas of long bones. Very limited genetic data have been published on CFOS.

METHODS

In the current study, we performed comprehensive genomic studies in 15 cases of high-grade CFOS by SNP array and targeted next generation sequencing.

RESULT

Our study shows high-grade CFOS demonstrate highly complex and heterogenous genomic alterations and harbor frequently mutated tumor suppressor genes TP53, CDKN2A/B, and PTEN, similar to conventional osteosarcomas. Potentially actionable gene amplifications involving CCNE1, AKT2, MET, NTRK1, PDGFRA, KDR, KIT, MAP3K14, FGFR1, and AURKA were seen in 43% of cases. GNAS hotspot activating mutations were also identified in a subset of CFOS cases, with one case representing malignant transformation from fibrous dysplasia, suggesting a role for GNAS mutation in the development of CFOS.

CONCLUSION

High-grade CFOS demonstrate highly complex and heterogenous genomic alterations, with amplification involving receptor tyrosine kinase genes, and frequent mutations involving tumor suppressor genes.

A Case Series and Literature Review of Craniofacial Fibrous Dysplasia

Craniofacial fibro-osseous lesions (CFOLs) are a diverse group of relatively rare entities whose etiology ranges from reactive to dysplastic with a potential for malignant transformation. It is distinguished by the replacement of bone with fibrous tissue, that subsequently develops different degrees of calcification. Fibrous dysplasia (FD) is a component of the fibro-osseous lesion spectrum. The clinical spectrum of FD is wide, ranging from minor monostotic lesions affecting a single bone to devastating polyostotic disease involving the entire skeleton. FD produces asymmetry, which impairs face aesthetics. FD leads to bone differentiation, disintegration, and disorganization. It depicts a cellular collagenous stroma lacking mitotic figures and pleomorphism. Blood capillaries are evenly distributed, as are elongated trabeculae of woven or lamellar bone with uneven curves (often referred to as the Chinese letters pattern). Three types of FD patterns can be identified by computed tomography (CT) imaging: a cystic pattern, a homogeneously dense pattern, and a ground-glass pattern. The cornerstone of treatment is surgery, although the method varies depending on the location, size, and symptoms of the lesion. As an alternative to surgery, the use of bisphosphonates to reduce osteoclastic activity is under consideration. In this case series, we present three cases of FD involving the maxilla and mandible. We aim to correlate the clinical presentation, histological features, and radiographic findings, to promote early diagnosis, treatment, and better prognosis of the patient.

Osteosarcoma Arising in Fibrous Dysplasia of the Long Bone: Characteristic Images and Molecular Profiles

Fibrous dysplasia (FD) is a benign fibro-osseous lesion that frequently involves the craniofacial bones and femur. Malignant transformation of FD is a rare occurrence. We report a 38-year-old woman with osteosarcoma (OS) arising from FD of the femur. Magnetic resonance imaging revealed a well-defined lesion in the medulla of the femur, with cortical thinning and local bone destruction. Wide excision of the femur was performed. Grossly, the inner part of the mass was hard and tan-gray in color, and the outer part of the mass adjacent to the cortex showed myxoid discoloration with infiltrative borders. Microscopically, most of the tumor consisted of curvilinear woven bone and fibrous stroma with bland spindle cells, which transitioned to the outer portion of the tumor, showing cellular proliferation of pleomorphic cells with frequent mitotic activity. Next-generation sequencing revealed GNAS and TP53 mutations, and the diagnosis of OS arising from FD was strongly supported. This case highlights the characteristic images and molecular features of the malignant transformation of FD.