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Background: Testicular Leydig cell tumours (LCTs) are the most common type of sex cord–stromal tumour in men, representing 1%–3% of all testicular neoplasms. Among testicular sex cord–stromal tumours, CTNNB1 mutations and nuclear expression of β‐catenin have been typically associated with Sertoli cell tumour. Recent genomic analyses have shown that CTNNB1 variants are also identified in a subset of LCTs; however, the frequency and clinicopathologic associations of β‐catenin alterations remain incompletely understood in this tumour type. Methods: In this study, we evaluated 32 LCTs (five malignant/metastasizing, 27 nonmetastasizing) using β‐catenin immunohistochemistry and DNA sequencing. Results: Immunohistochemistry revealed focal or multifocal nuclear β‐catenin expression in 47% of the tumours. Diffuse nuclear β‐catenin expression (in >50% of the tumour cells) was not detected in any of the cases analysed herein. Comparison of β‐catenin‐positive and β‐catenin‐negative cases did not show significant differences in the frequency of adverse histopathologic findings or malignant clinical behaviour. DNA sequencing performed de novo on a subset of seven cases revealed the presence of exon 3 CTNNB1 variants in four of them (4/7, 57%), with variant allele frequencies (VAF) ranging from 7 to 33%. Two additional β‐catenin‐positive cases that had been sequenced as part of a previous study harboured exon 3 CTNNB1 variants at VAF of 28% and 7%, respectively. Conclusion: These results demonstrate that β‐catenin alterations are relatively common in LCT, most likely occurring as subclonal events that are not enriched in cases with aggressive features. Further studies are needed to clarify the oncogenic role of β‐catenin in this tumour type. [ABSTRACT FROM AUTHOR]

Leydig Cell Tumor (LCT) is very rare in adults. It constitutes only 1% of total testicular tumors. LCTs can produce steroid hormones such as estrogen, progesterone, and testosterone. Sertoli cells are found in seminiferous tubules, they are part of the blood-testis barrier. Sertoli Cells Only Syndrome (SCOS) also known as germ cell aplasia is characterized by azoospermia in which the seminiferous tubules of testicular biopsy are lined only with Sertoli cells. The expected hormone profile in SCOS is increased FSH with normal T and LH. The expected hormone profile in LCT is increased/normal FSH and LH with increased T or E2. A patient presented to our clinic with a well-circumscribed mass in his right testicle and underwent radical orchiectomy. Tumor markers were negative. Azoospermia was detected in the spermiogram. T and E2 were normal, FSH, and LH were high. Right radical orchiectomy was performed. A combination of LCT and SCOS were reported in pathology results. Azoospermia cases secondary to high androgen levels are frequently encountered in LCTs. As in the case we have presented, two different testicular pathologies may present at the same time and create an unexpected hormonal picture. Such situations can cause the laboratory to mask the clinical truth. [ABSTRACT FROM AUTHOR]

Fumarate hydratase, Leydig cell tumour, HLRCC, testis, sex cord-stromal tumour More specifically, there is evidence that at least some FH-deficient LCTs are associated with germline I FH i mutations/HLRCC and FH-deficiency appears to be more common in (albeit likely not exclusive to) neoplasms with aggressive histopathologic features and/or malignant clinical behaviour. Keywords: fumarate hydratase; HLRCC; Leydig cell tumour; sex cord-stromal tumour; testis EN fumarate hydratase HLRCC Leydig cell tumour sex cord-stromal tumour testis 646 647 2 02/09/23 20230301 NES 230301 Leydig cell tumour (LCT) is the most common type of testicular sex cord-stromal tumour (TSCST) and demonstrates a biphasic incidence, with peaks in childhood and early to mid-adulthood, respectively. [Extracted from the article]