Surprising genetic and pathological findings in a patient with giant bilateral periadrenal tumours: PEComas and mutations of PTCH1 in Gorlin-Goltz syndrome

Radiological evaluation of odontogenic keratocysts in patients with nevoid basal cell carcinoma syndrome: A review

Background

Nevoid Basal Cell Carcinoma Syndrome (NBCCS) is an autosomal dominant syndrome that has various expressions in each patient. Generally; NBCCS is followed by multiple nevoid basal cell carcinoma of the skin, orbital anomalies, skeletal anomalies, central nervous system anomalies and multiple odontogenic keratocysts (OK). NBCCS is usually diagnosed between the ages of 5-30 years, with multiple basal cell carcinomas of the skin and OKs in the jaws as the initial findings. The purpose of this paper is to describe and compare the radiographic findings of the OKs in NBCCS patients in the literature with additional cases.

Materials and Methods

In this study, we evaluated the OKs of the patients with NBCCS in PubMed Database with 5 additional cases from our database. A total of 305 articles were found and the articles in English with full-text access were evaluated.

Results

Despite all limitations for a fair discussion; we would like to state that among 59 cases that specified whether a 3D or 2D imaging modality was used, 29 cases were only interpreted with 2D data which should be avoided in OK evaluation.

Discussion

According to the World Health Organization's Classification of Head and Neck Tumours Book which was published in 2017, OKs in NBCCS has a higher chance to have small satellite cystic lesions which increase their recurrence possibility post-operatively, thus, a thorough clinical and 3D radiographic evaluation should be performed both to NBCCS patients and non-syndromic OK patients to avoid any recurrence.

Conclusion

High recurrence rates of OKs should be reminded all the time. Radiographic examinations with 3D imaging modalities should be done in patients with NBCCS in order to provide a concise diagnosis and optimum treatment.

Genome sequencing-based discovery of a novel deep intronic APC pathogenic variant causing exonization

Familial adenomatous polyposis (FAP) is a hereditary cancer syndrome that occurs as a result of germline mutations in the APC gene. Despite a clear clinical diagnosis of FAP, a certain proportion of the APC variants are not readily detectable through conventional genotyping routines. We accomplished genome sequencing in duo of the disease-affected proband and non-affected sibling followed by in silico predictions and a series of RNA-based assays clarifying variant functionality. By prioritizing variants obtained by genome sequencing, we discovered the novel deep intronic alteration APC:c.531 + 1482 A > G that was demonstrated to cause out-of-frame exonization of 56 base pairs from intron 5 of the gene. Further cDNA assays confirmed, that the aberrant splicing event was complete and its splice product was subject to nonsense-mediated decay. Co-segregation was observed between the variant carrier status and the disease phenotype. Cumulative evidence confirmed that APC:c.531 + 1482 A > G is a pathogenic variant causative of the disease.

Case Report: A Novel Pathomechanism in PEComa by the Loss of Heterozygosity of TP53

Since the introduction of next-generation sequencing, the frequency of germline pathogenic TP53 variants and the number of cases with unusual clinical presentations have been increasing. This has led to the expansion of the classical Li–Fraumeni syndrome concept to a wider cancer predisposition syndrome designated as the Li–Fraumeni spectrum. Here, we present a case with a malignant, metastatic perivascular epithelioid cell tumor (PEComa) of the thigh muscle and a sinonasal carcinoma harboring a novel TP53 germline splice mutation (NM_000546.5:c.97-2A>C). The classical presentation of LFS in the long-since deceased mother and the presence of a germline TP53 variant in the proband suggested a possible familial TP53-related condition. Complex pathological, molecular, and clinical genetic analyses (whole exome sequencing of germline variants, multigene panel sequencing of tumor DNA, Sanger validation, an in vitro functional test on splicing effect, 3D protein modeling, p53 immunohistochemistry, and pedigree analysis) were performed. The in vitro characterization of the splice mutation supported the pathogenic effect that resulted in exon skipping. A locus-specific loss of heterozygosity in the PEComa but not in the sinonasal carcinoma was identified, suggesting the causative role of the splice mutation in the PEComa pathogenesis, because we excluded known pathogenetic pathways characteristic to PEComas (TSC1/2, TFE3, RAD51B). However, the second hit affecting TP53 in the molecular pathogenesis of the sinonasal carcinoma was not identified. Although PEComa has been reported previously in two patients with Li–Fraumeni syndrome, to the best of our knowledge, this is the first report suggesting a relationship between the aberrant TP53 variant and PEComa.