Molecular Basis and Diagnostic Approach to Isolated and Syndromic Lateralized Overgrowth in Childhood.

OBJECTIVE: To demonstrate a high-yield molecular diagnostic workflow for lateralized overgrowth (LO), a congenital condition with abnormal enlargement of body parts, and to classify it by molecular genetics. and STUDY DESIGN: We categorized 186 retrospective cases of LO diagnosed between 2003 and 2023 into suspected Beckwith-Wiedemann spectrum (BWSp), PIK3CA-Related Overgrowth Spectrum (PROS), vascular overgrowth (VO) , or isolated (ILO), based on initial clinical assessments, to determine the appropriate first-tier molecular tests and tissue for analysis. Patients underwent testing for 11p15 epigenetic abnormalities or somatic variants in genes related to PI3K/AKT/mTOR, vascular proliferation, and RAS-MAPK cascades using blood or skin DNA. For cases with negative initial tests, a sequential cascade molecular approach was employed to improve diagnostic yield. RESULTS: This approach led to a molecular diagnosis in 54% of cases, 89% of cases consistent with initial clinical suspicions and 11% reclassified. BWSp was the most common cause, with 43% of cases exhibiting 11p15 abnormalities. PROS had the highest confirmation rate, with 74% of clinically diagnosed patients showing a PIK3CA variant. VO demonstrated significant clinical overlap with other syndromes. Molecular diagnosis of ILO proved challenging, with only 21% of cases classifiable into a specific condition. CONCLUSION: Despite, LO is underdiagnosed from a molecular viewpoint and to date has had no diagnostic guidelines, which would be crucial for addressing potential cancer predisposition, enabling precision medicine treatments, or guiding management. This study sheds light on the molecular etiology of LO, highlighting the importance of tailored diagnostic approach and of selecting appropriate testing to achieve the highest diagnostic yield.

Successful treatment with MEK-inhibitor in a patient with NRAS-related cutaneous skeletal hypophosphatemia syndrome.

Cutaneous skeletal hypophosphatemia syndrome (CSHS) is caused by somatic mosaic NRAS variants and characterized by melanocytic/sebaceous naevi, eye, and brain malformations, and FGF23-mediated hypophosphatemic rickets. The MEK inhibitor Trametinib, acting on the RAS/MAPK pathway, is a candidate for CSHS therapy. A 4-year-old boy with seborrheic nevus, eye choristoma, multiple hamartomas, brain malformation, pleural lymphangioma and chylothorax developed severe hypophosphatemic rickets unresponsive to phosphate supplementation. The c.182A > G;p.(Gln61Arg) somatic NRAS variant found in DNA from nevus biopsy allowed diagnosing CSHS. We administered Trametinib for 15 months investigating the transcriptional effects at different time points by whole blood RNA-seq. Treatment resulted in prompt normalization of phosphatemia and phosphaturia, catch-up growth, chylothorax regression, improvement of bone mineral density, reduction of epidermal nevus and hamartomas. Global RNA sequencing on peripheral blood mononucleate cells showed transcriptional changes under MEK inhibition consisting in a strong sustained downregulation of signatures related to RAS/MAPK, PI3 kinase, WNT and YAP/TAZ pathways, reverting previously defined transcriptomic signatures. CSHS was effectively treated with a MEK inhibitor with almost complete recovery of rickets and partial regression of the phenotype. We identified "core" genes modulated by MEK inhibition potentially serving as surrogate markers of Trametinib action.

A new case of Smith-Kingsmore syndrome with somatic MTOR pathogenic variant expands the phenotypic spectrum to lateralized overgrowth.

Smith-Kingsmore syndrome (SKS) is a rare autosomal dominant disorder caused by heterozygous germline activating pathogenic variants in mammalian target of rapamycin (MTOR) on chromosome 1p36. A few patients with disseminated mosaicism have been described so far and they seem to display a different phenotype when compared to germline cases. Here we report the sixth case with a disseminated mosaic MTOR pathogenic variant, a 7-year-old boy with hemimegalencephaly, epilepsy, developmental delay, hypomelanosis of Ito, and lateralized overgrowth. Genetic testing revealed a pathogenic variant (c.4448G > A, p.Cys1483Tyr) in MTOR with a frequency of 32% in the DNA extracted from a skin sample, 3% in saliva and 0.46% in blood. The clinical features observed in our patient further corroborate the existence of differences in phenotypic presentation of germline and mosaic SKS cases. Moreover, lateralized overgrowth, a finding never described so far in SKS, further expands the phenotypic spectrum of SKS and allows the inclusion of MTOR pathogenic variants among the several causes of asymmetric body overgrowth.

Kaposiform hemangioendothelioma further broadens the phenotype of PIK3CA-related overgrowth spectrum.

Kaposiform hemangioendothelioma (KHE) is a rare locally aggressive mixed vascular tumor, with typical onset in early childhood and characterized by progressive angio- and lymphangiogenesis. Its etiopathogenesis and molecular bases are still unclear. Here, we report the first case of congenital KHE harboring a PIK3CA mosaic pathogenic variant (c.323G > A, p.Arg108His) in a boy with very subtle PIK3CA-related overgrowth spectrum (PROS) features. This finding provides insights into the pathophysiology of KHE, offering targeted therapeutic options by inhibition of the PI3K/Akt/mTOR pathway. We propose the inclusion of this mixed lymphatic and vascular anomaly within the PROS.

Epidemiology of the disorders of the Pik3ca-related overgrowth spectrum (Pros).

PIK3CA pathogenic variants are responsible for a group of overgrowth syndromes, collectively known as PIK3CA-Related Overgrowth Spectrum (PROS). These gain-of-function variants arise postzygotically, and, according to time of onset, kind of embryonal tissue affected and regional body extension, give rise to heterogeneous phenotypes. PROS rarity and heterogeneity hamper the correct estimation of its epidemiology. Our work represents the first attempt to define the prevalence of PROS according to the established diagnostic criteria and molecular analysis and based on solid demographic data. We assessed the prevalence in Piedmont Region (Italy), including in the study all participants diagnosed with PROS born there from 1998 to 2021. The search identified 37 cases of PROS born across the 25-year period, providing a prevalence of 1:22,313 live births. Molecular analysis was positive in 81.0% of participants. Taking into account the cases with a detected variant in PIK3CA (n = 30), prevalence of molecularly positive PROS was 1:27,519.

Systemic Treatment Initiation in Classical and Endemic Kaposi's Sarcoma: Risk Factors and Global Multi-State Modelling in a Monocentric Cohort Study.

BACKGROUND: Although several studies described the clinical course of epidemic and post-transplant Kaposi's Sarcoma (KS), the lack of large cohorts of classic/endemic KS, precluded such characterization. METHODS: We used multi-state modelling in a retrospective monocentric study to evaluate global disease evolution and identify risk factors for systemic treatment (ST) initiation. 160 classic/endemic KS patients consecutively diagnosed between 1990 and 2013 were included. RESULTS: 41.2% of classic/endemic KS patients required ST. Cumulative incidence of ST after 2 years of follow-up was 28.4% [95% CI: 20.5; 35.5]. Multivariate analysis identified six risk factors for ST initiation: time between first symptoms and diagnosis ≥1 year, endemic KS, total number of lesions ≥10, visceral, head or neck localization and presence of edema. Type of ST, type of KS, age and time between diagnosis and ST were not associated with response. Mean treatment-free time during the first 5 years following ST was 44 months for interferon and 44.6 months for chemotherapy treated patients (Mean difference: -0.5 months [95% CI: -9.5; 4.9]). CONCLUSIONS: Our study reveals ST risk factors in classic/endemic KS and highlights the clinical aggressiveness of the endemic KS subtype. No efficacy difference was observed between standard of care treatments, enabling treatment choice based on patient's fitness.

Primary cutaneous B-cell lymphoma: narrative review of the literature.

Primary cutaneous B-cell lymphomas comprehend a group of lymphoproliferative disorders characterized by being monoclonal proliferations of B-cell primarily involving the skin. Despite being recognized as autonomous and distinct clinico-pathologic entities since the late 80s, their classification is still an ongoing matter of debate. At the moment, WHO classification recognizes three disorders: primary cutaneous marginal zone lymphoma, primary cutaneous follicle center lymphoma and primary cutaneous diffuse large b-cell lymphoma (leg type). Primary cutaneous diffuse large b-cell lymphoma (other) has been used to define rare cases which show histologically an infiltrate with diffuse pattern composed by large b-cell, but not fitting with criteria for follicle center lymphoma nor for primary cutaneous diffuse large b-cell lymphoma (leg type). Aim of this review was to briefly describe all recognized and provisional entities included in the primary cutaneous b-cell lymphomas and to discuss recent acquisitions that may influence their future classifications.

18F-fluorodeoxyglucose-positron emission tomography is more sensitive than computed tomography in initial staging of patients with an anaplastic T-cell lymphoma first presenting in the skin.

BACKGROUND: The role of 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET) in the evaluation of anaplastic large-cell lymphoma (ALCL) first presenting in the skin is not well established, while computed tomography (CT) is used as a standard procedure. OBJECTIVES: The aim of this study was to evaluate the use of FDG-PET versus CT at initial staging of ALCL first presenting in the skin. MATERIALS & METHODS: Eleven cases of ALCL first presenting in the skin who underwent both FDG-PET and CT were retrospectively analysed. There were six males and five females, with a mean age of 59.7 years. Results of FDG-PET were compared with those of CT. Biopsy results of lesions served as a reference for the accuracy of PET and CT in the evaluation of local and metastatic lesions. RESULTS: In seven cases (64%), imaging revealed extracutaneous ALCL. FDG-PET results were concordant with CT results in five cases (45%); in four of these cases, FDG-PET was negative, consistent with CT, and one case had cutaneous and extracutaneous lesions detectable on both CT and FDG-PET. FDG-PET and CT were discordant in six cases (55%). Among these six cases, FDG-PET revealed extracutaneous lesions undetected on CT which consequently influenced the therapeutic decision in five cases (45%). CONCLUSION: The sensitivity of CT and FDG-PET was 18% and 64%, respectively.