Secondary desmoplastic fibroma-like tissue changes in mandibular fibrous dysplasia: clinicopathological and molecular study of a case

Nanostring technology on Fibrous Dysplasia bone biopsies. A pilot study suggesting different histology-related molecular profiles

Identifying the molecular networks that underlie Fibrous Dysplasia (FD) is key to understand the pathogenesis of the disease, to refine current diagnostic approaches and to develop efficacious therapies. In this study, we used the NanoString nCounter Analysis System to investigate the gene signature of a series of nine Formalin Fixed Decalcified and Paraffin-Embedded (FFDPE) bone biopsies from seven FD patients.

We analyzed the expression level of 770 genes. Unsupervised clustering analysis demonstrated partitioning into two clusters with distinct patterns of gene expression. Differentially expressed genes included growth factors, components of the Wnt signaling system, interleukins and some of their cognate receptors, ephrin ligands, matrix metalloproteinases, neurotrophins and genes encoding components of the cAMP-dependent protein kinase. Interestingly, two tissue samples obtained from the same skeletal site of one patient one year apart failed to segregate in the same cluster. Retrospective histological review of the samples revealed different microscopic aspects in the two groups.

The results of our pilot study suggest that the genetic signature of FD is heterogeneous and varies according to the histology and, likely, to the age of the lesion. In addition, they show that the Nanostring technology is a valuable tool for molecular translational studies on archival FFDPE material in FD and other rare bone diseases.

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We used the NanoString technology to analyze Formalin Fixed Decalcified Paraffin Embedded (FFDPE) Fibrous Dysplasia samples.

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We show that Fibrous Dysplasia lesions may have different molecular profiles consistent with its histological heterogeneity.

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NanoString technology is a valuable tool for molecular studies on rare bone diseases by using FFDPE archival material.

Successful Intravascular Treatment of an Intraosseous Arteriovenous Fistula in Fibrous Dysplasia

Fibrous dysplasia (FD) is a benign bone disease characterized by expansile lesions that typically stabilize with age. Rarely, FD can undergo malignant transformation, presenting with atypical, rapid growth and destruction of adjacent bone. Other potential causes of rapid FD expansion include secondary lesions, such as aneurysmal bone cysts. We describe a case of an aggressive occipital lesion that presented with pain associated with diplopia and tinnitus, raising concern for malignant transformation. A massive intraosseous arteriovenous fistula was identified giving rise to an anomalous vein coursing to the cavernous sinus with compression of the abducens nerve. The vascular anomaly was mapped and after embolization symptoms resolved; a biopsy with extensive genetic analyses excluded malignancy. The differential diagnosis for expanding FD lesions includes aggressive FD, malignant transformation, and secondary vascular anomalies. In cases when traditional radiographic and histologic assessments are nondescript, use of additional radiographic modalities and genetic analyses are required to make an accurate diagnosis and guide treatment. When vascular anomalies are suspected, detailed angiography with embolization is necessary to define and treat the lesion. However, to rule out malignant transformation, genetic screening is recommended.