Edgar, Mark

Abstract Disclosure: S. Thota-Kammili: None. J.A. McNeil: None. S.J. Peres: None. M.A. Edgar: None. J.P. Reynolds: None. J. Eleazer: None. A.Y. Chang: None. Introduction: 45,X/46,X,psrY mosaicism has been reported in the context of prenatal diagnosis with few reports on the developmental phenotype through adulthood. The 45,X/46,XY karyotype is well-studied and linked to ambiguous genitalia, dysgenetic gonads, and increased gonadal tumor risk. Less is known about 45,X/46,X,psrY mosaicism, characterized by partial Y chromosome retention. Phenotypic variability with a broad spectrum of phenotypes including Turner syndrome features, delayed puberty, hypogonadism and infertility depends on the extent and functionality of preserved Y chromosome material. We present a case of 45,X/46,X,idic(Y)(q11.21) mosaicism in an individual assigned male at birth, with a nonbinary intersex gender identity who received gender affirming feminizing hormone therapy (GAHT) before orchiectomy. Clinical Case: This is a case of a 36 y.o. patient who was found to have 45,X/46,X +mar chromosomal abnormality prenatally and initially diagnosed with Turner’s syndrome. At birth, patient had male genitalia, descended testes, and only slight hypospadias. Subsequent Y-DNA studies determined the unknown marker to be the sex determining region of the Y chromosome. Early evaluations showed appropriate responses to LHRH and ACTH, and developmental milestones were met without major health or behavioral concerns aside from a delay in puberty. The patient experienced early gender incongruence and faced questioning for gender expression. Delayed puberty led to testosterone therapy, worsening distress. Parents did not share the medical history with the patient until adulthood, when they notified them about the potential for infertility. During infertility evaluation, semen analysis revealed azoospermia. Testosterone therapy was re-attempted for hypogonadism but resulted in increased distress and patient began GAHT. Patient sought a second opinion on previous diagnosis of differences of sexual development (DSD). Chromosomal analysis revealed the 45,X/46,X,idic(Y)(q11.21) mosaicism, with duplication of Yp and deletion of the Yq. Pt was referred to urology for bilateral orchiectomy to reduce gonadal tumor risk and gender dysphoria. Pathology revealed atrophic seminiferous tubules with complete absence of spermatogenesis which were populated by Sertoli cells only and surrounded by thickened basal lamina. Leydig cells were markedly depleted. These changes are seen in transgender patients treated with estrogen prior to orchiectomy. Conclusion: Our case expands the phenotypic characterization of 45,X/46,X,idic(Y)(q11.21) mosaicism by detailing clinical features and previously unreported testicular pathology. This patient had minimal developmental concerns, and testicular pathology reflected changes associated with GAHT, highlighting the variability in phenotypic expression of 45,X/45,X,psrY mosaicism. Presentation: Sunday, July 13, 2025

Background Spinal subdural empyema rarely involves the spinal cord and may result in devastating neurological deficits. These lesions typically require prompt diagnosis, surgical evacuation, and antibiotic therapy. Here, we present the clinical course, imaging, and narrated operative video of a thoracic spinal subdural empyema initially diagnosed as an intramedullary neoplasm. Case Description A 73-year-old female presented with a 6-month history of worsening thoracic myelopathy; over the last few weeks, she rapidly developed paraplegia. She was initially diagnosed with an enlarging thoracic intramedullary mass. A spinal biopsy was performed for the presumptive diagnosis of primary intramedullary central nervous system lymphoma. However, at surgery, the thoracic lesion proved to be a chronic subdural empyema (i.e., surrounded by arachnoid granulations and soft-purulent tissue). Interestingly, the operative specimen failed to grow any specific organism. Conclusion Spinal subdural empyema should be one of the differential diagnoses considered for patients presenting with intradural spinal cord lesions.

Abstract Most TERT promoter (TERTp) clinically relevant sequence variants in CNS tumors are the canonical C228T and C250T mutations. Non-canonical TERTp mutations have been reported mainly in non-CNS tumors. We describe 12 CNS tumors with non-canonical TERTp variants interpreted as clinically relevant. Using clinical targeted NGS panels (2020-2024), we detected c.-100_-79dup (n=2), c.-92_-91insGGCGGCCCCGCCCCTTCCTTTC (n=1), c.-118_-117insTCCCCGGCCCAGCCCCTTCCGGG (n=1), c.-123_-76dup (n=1), c.-110_-89dup (n=2), and c.-57A>C (n=5). Most cases had chromosomal microarray (n=11) and/or methylation array data analyzed using the NCI/Bethesda v.2 classifier (n=9). All non-canonical TERTp variants occurred at a variant allele frequency suggestive of somatic clonal origin (mean, 34%; range, 18-46), and in adults (mean age, 60 years; range, 36-88). Except for the c.-57A>C variant, all non-canonical TERTp variants occurred in tumors with histological and/or molecular diagnostic features of glioblastoma, IDH-wildtype (GBM), often epigenetically aligning to this tumor type. All five tested cases matched to superfamily glioblastoma (score ≥ 0.9), with three to class GBM_RTK_I (>0.9 in 2, 0.86 in 1) and two to GBM_RTK_II (>0.9). The size and sequence of such variants suggest that these may be functionally equivalent to canonical mutations or generate favorable TERTp activation motif conformations like previously reported activating duplications. The c.-57A>C variant is a well-established oncogenic mutation observed in other cancer types but has not been reported in CNS tumors. We describe five cases with the c.-57A>C variant: one GBM matching to methylation class GBM_MES_TYP (0.99); two oligodendroglioma, IDH-mutant and 1p/19q-codeleted, one of which had methylation data matching to class O_IDH (0.99); one diffuse glioma, IDH-mutant, which was partially 1p/19q-codeleted and matched to class O_IDH (0.99); and one anaplastic meningioma, aligning to superfamily meningioma (0.99)/MNG_MAL (0.79). Our findings show that non-canonical TERTp variants typically occur in tumor types that often harbor TERTp canonical mutations, expanding the spectrum of TERTp clinically relevant variants that are molecular biomarkers in CNS tumors.

A 74-year-old male presented with rectal pain; workup uncovered an anal mass, and a diagnosis of melanoma was rendered via histologic examination and immunohistochemical (IHC) studies. Droplet digital PCR (ddPCR)–based BRAF testing was performed and revealed the presence of BRAF V600E, which is a common targetable genetic alteration in melanoma. Interestingly, the ratio of mutant to wild-type copy number was low (0.3%), whereas tumor cell percentage on tissue slides was 90%. With additional workup, BRAF V600E IHC confirmed a very small subset of BRAF V600E–positive cells, and a next-generation sequencing (NGS) panel revealed a pathogenic KIT variant, p.L576P, with an allele frequency of 63%. It was initially hypothesized that the main driver of the melanoma was the KIT alteration, whereas a small subclone (not detected by NGS, which has a 5% limit of detection) was driven by the BRAF V600E detected by ddPCR. To determine whether there were morphologic differences between the 2 clones, a careful review of the histology was performed and revealed distinct morphology of the BRAF V600E–positive cells, including pale cytoplasm, nuclear grooves, and infiltrating eosinophils. Additional IHC workup of the BRAF V600E–positive cells showed coexpression of CD1a, Langerin, and S100, diagnostic of Langerhans cell histiocytosis (LCH). This diagnosis was unexpected and would have been missed without highly sensitive molecular testing; yet it is of clinical importance for the patient. This case raises interesting biology questions regarding the relationship between melanoma and LCH; moreover, it highlights the importance of integrating quantitative information in molecular data interpretation.