👤 Maria Gnoli

Multiple osteochondromas (MO) is an autosomal dominant disorder and the most common genetic skeletal dysplasia, characterized by the growth of bone outgrowths capped by cartilage, called osteochondromas. Most MO cases are caused by mutations in the exostosin-1 ( Show less

Despite the new next-generation sequencing (NGS) molecular approaches implemented the genetic testing in clinical diagnosis, copy number variation (CNV) detection from NGS data remains difficult mainly in the absence of bioinformatics personnel (not always available among laboratory resources) and when using very small gene panels that do not meet commercial software criteria. Furthermore, not all large deletions/duplications can be detected with the Multiplex Ligation-dependent Probe Amplification (MLPA) technique due to both the limitations of the methodology and no kits available for the most of genes. We propose our experience regarding the identification of a novel large deletion in the context of a rare skeletal disease, multiple osteochondromas (MO), using and validating a user-friendly approach based on NGS coverage data, which does not require any dedicated software or specialized personnel. The pipeline uses a simple algorithm comparing the normalized coverage of each amplicon with the mean normalized coverage of the same amplicon in a group of "wild-type" samples representing the baseline. It has been validated on 11 samples, previously analyzed by MLPA, and then applied on 20 patients with MO but negative for the presence of pathogenic variants in All the 11 known CNVs (exon and multi-exon deletions) have been detected with a sensitivity of 97.5%. A novel In addition to enhancing the variant detection rate in MO molecular diagnosis, this easy-to-use approach for CNV detection can be easily extended to many other diagnostic fields-especially in resource-limited settings or very small gene panels. Notably, it also allows partial-exon deletion detection. Show less

Secondary peripheral chondrosarcomas arising in solitary osteochondromas is an unusual complication, reported in small series. In this study, we aimed to present our experience with this rare variant of chondrosarcoma and compare results with already published data in order to determine prognostic factors for overall and disease-free survival. The case study includes retrospective data from patients diagnosed at a single institution from 1943 to 2019. Clinical data were collected reviewing all available medical records from first to last follow-up visits. To exclude the presence of the Multiple Osteochondroma Hereditary Syndrome, few patients, with a suspect of a familial form of the disease, were evaluated for the presence of germline heterozygous variants in EXT1 and EXT2 genes. Results were summarized using descriptive statistics and statistical analysis were performed to reveal associations between variables. Two hundred and fourteen secondary peripheral chondrosarcomas that arose exclusively from solitary osteochondromas diagnosed in a multidisciplinary setting at the IRCCS Istituto Ortopedico Rizzoli were retrospectively identified, 66.4% males and 33.6% females with a median age at diagnosis of 38 years. The local recurrence rate was 17.3%, while the metastases one was 5.1%. Besides age, a high histologic grade is the only factor associated with worse 5-year and 10-year overall survival (log-rank p = 0.0005, HR = 3.74; 95% CI 1.69-8.26). Moreover, high histological grade (HR = 3.75; 95% CI = 1.69-8.34; p = 0.001) and surgical debulking (HR = 3.71; 95% CI = 1.57-8.79; p = 0.003) were associated with a significantly worse disease-free survival. Our study confirm the low-grade behavior of secondary peripheral chondrosarcomas and demonstrate that the best choice of treatment for those arising in solitary osteochondromas is the wide surgical excision, when possible. Location per se is not a factor that affects prognosis, while the accurate histological grade assessment is correlated with the tumor aggressiveness and a long term follow up is necessary for this rare variant of chondrosarcoma. Show less