Beckwith-Wiedemann syndrome (BWS) is a rare genetic and cancer-predisposing disorder characterized by variable clinical and molecular abnormalities. It is considered a spectrum ranging from classical BWS to isolated hemihyperplasia (IHH). This study sought to characterize Omani patients with BWS and IHH clinically and molecularly, evaluate their surveillance results, and assess the tumor's prevalence in the cohort. Nine patients with BWS were retrospectively recruited to the study by searching the medical records of Sultan Qaboos University Hospital between January 2012 and December 2022. Demographics, clinical features, molecular findings, and surveillance test results, including abdominal ultrasound and alpha-fetoprotein, were extracted from the hospital information system and systematically analyzed. Nine patients diagnosed with Beckwith-Wiedemann syndrome were studied, comprising four BWS cases and five IHH cases. Macroglossia was the predominant clinical feature among BWS patients, whereas lateralized overgrowth was consistently observed in IHH patients. All BWS patients tested positive for methylation anomalies: two exhibited loss of methylation at imprinting control 2 (22.2%), one had paternal uniparental disomy of chromosome 11 (11.1%), and another showed a gain of methylation at imprinting control 1 (11.1%). Throughout the surveillance period, none of the patients showed elevated alpha-fetoprotein levels or developed tumors. This is the first study to examine a cohort of patients with BW spectrum in Oman. It reveals comparable clinical and molecular characteristics to the previously reported BWS patients, yet no tumors were detected in this cohort.

Beckwith-Wiedemann syndrome (BWS) is a genomic imprinting disorder caused by diverse genetic and/or epigenetic disorders of chromosome 11p15.5. BWS presents with a variety of clinical features, including overgrowth and an increased risk of embryonal tumors. Notably however, reports of patients with BWS and breast tumors are rare, and the association between these conditions is still unclear. Insulin-like growth factor-2 (IGF2) expression is known to be associated with the development of various cancers, including breast cancer, and patients with BWS with specific subtypes of molecular defects are known to show characteristic clinical features and IGF2 overexpression. A 17-year-old girl who had been diagnosed with BWS based on an umbilical hernia, hyperinsulinemia, and left hemihypertrophy at birth, visited our department with a gradually swelling left breast. Her left breast was markedly larger than her right breast on visual examination. Imaging examinations showed two tumors measuring about 10 cm each in the left breast, and she was diagnosed with juvenile fibroadenoma following core needle biopsy. The two breast tumors were removed surgically and the patient remained alive with no recurrence. The final diagnosis was juvenile fibroadenoma without malignant findings. Immunohistochemical staining using IGF2 antibody revealed overexpression of IGF2 in the cytoplasm of ductal epithelial cells. Because of her clinical features and IGF2 overexpression, molecular defects of 11p15.5 including a possible genetic background of paternal uniparental disomy of chromosome 11 or hypermethylation of imprinting center 1 was suspected. In this case, overexpression of IGF2 suggested a possible relationship between BWS and breast tumors. Moreover, the characteristic clinical features and IGF2 staining predicted the subtype of 11p15.5 molecular defects in this patient.

Placental mesenchymal dysplasia (PMD) is characterized by placentomegaly, aneurysmally dilated chorionic plate vessels, thrombosis of the dilated vessels, and large grapelike vesicles, and is often mistaken for partial or complete hydatidiform mole with a coexisting normal fetus. Androgenetic/biparental mosaicism (ABM) has been found in many PMD cases. Beckwith-Wiedemann syndrome (BWS) is an imprinting disorder with complex and diverse phenotypes and an increased risk of developing embryonal tumors. There are five major causative alterations: loss of methylation of imprinting control region 2 (KCNQ1OT1:TSS-DMR) (ICR2-LOM), gain of methylation at ICR1 (H19/IGF2:IG-DMR) (ICR1-GOM), paternal uniparental disomy of 11 (pUPD11), loss-of-function variants of the CDKN1C gene, and paternal duplication of 11p15. Additional minor alterations include genetic variants within ICR1, paternal uniparental diploidy/biparental diploidy mosaicism (PUDM, also called ABM), and genetic variants of KCNQ1. ABM (PUDM) is found in both conditions, and approximately 20% of fetuses from PMD cases are BWS and vice versa, suggesting a molecular link. PMD and BWS share some molecular characteristics in some cases, but not in others. These findings raise questions concerning the timing of the occurrence of the molecularly abnormal cells during the postfertilization period and the effects of these abnormalities on cell fates after implantation.

Paternal uniparental disomy of chromosome 11 (upd(11)pat) accounts for up to 20% of molecularly confirmed Beckwith-Wiedemann spectrum (BWSp) cases. It belongs to the BWSp subgroup with the second highest tumor risk, and therefore needs particular awareness in research, diagnostics and clinical management. We overview the contribution of paternal (mosaic) uniparental disomy of chromosome 11 (UPD, upd(11)pat) and mosaic paternal uniparental diploidy in patients with Beckwith-Wiedemann features. The review comprises the current knowledge on their formation and their molecular and clinical consequences. Accordingly, the consequences for diagnostic testing and clinical monitoring are compiled. The necessity to diagnostically identify and thus discriminate genome-wide paternal uniparental disomy, and upd(11)pat becomes obvious, due to the differences in the clinical course, disease prognosis, and treatment. In particular, monitoring of tumor development by liquid biopsy might be a promising option in the future. From the research point of view, it should be addressed why 11p is prone to mitotic recombination and thus also provide to the role of upd(11) as second hit in tumorigenesis.

Pediatric adrenocortical tumors (ACTs) are rare and heterogeneous. Approximately 50% of children with ACT carry a germline TP53 variant; however, the genetic underpinning of remaining cases has not been elucidated. In patients having germline TP53 variants, loss of maternal chromosome 11 and duplication of the paternal copy [paternal uniparental disomy, (UPD)] occurs early in tumorigenesis and explains the overexpression of IGF2, the hallmark of pediatric ACT. Beckwith-Wiedemann syndrome (BWS) is also associated with overexpression of IGF2 due to disruption of the 11p15 loci, including segmental UPD. Here, we report six children with ACT with wild type TP53 and germline paternal 11p15 UPD. Median age of five girls and one boy was 3.2 years (range 0.5-11 years). Two patients met the criteria for BWS before diagnosis of ACT. However, ACT was the first and only manifestation of paternal 11p15 UPD in four children. Tumor weight ranged from 21.5 g to 550 g. Despite poor prognostic features at presentation, such as pulmonary metastasis, bilateral adrenal involvement, and large tumors, all patients are alive 8-21 years after cancer diagnosis. Our observations suggest that children with ACT and wild type TP53, irrespective of their age, should be screened for germline abnormalities in chromosome 11p15.