Introduction/Background Turner syndrome (TS) is a multisystem syndrome characterized by monosomy X. Cancer risks in women with TS are particularly still controversial, and the association between hidden Y chromosome material and the risk of gonadoblastome seems to be well-established. This study explores this association while detecting hidden Y chromosome in TS females seen at our genetic counselling.

Methodology A cohort of 26 TS females underwent cytogenetic assessment using conventional cytogenetic methods and fluorescence in situ hybridization (FISH). DNA samples were collected for multiplex PCR analysis to assess the presence of Y chromosome material.

Results Three cases exhibited complete and pure monosomy X, while 14 cases had complete monosomy X with a 46,XX mosaic. Nine cases displayed partial monosomy X with X or Y structural abnormalities, with or without a 45,X cell line. A single patient had a mosaic chromosomal formula with both 45,X and 46,XY cell populations. FISH analysis confirmed the presence of an isoYq-rearranged chromosome with a solitary secondary constriction. Multiplex PCR analysis revealed Y chromosome material in only one patient with an isoYq-rearranged chromosome (3.8%). The remaining 25 TS females tested negative for Y chromosome material. No cancer diagnoses were found in the cohort. The TS patient with Y chromosome material exhibited female-type external genitalia and a small infantile uterus on abdominal Magnetic Resonance Imaging, without identifiable gonads.

Conclusion The presence of detected Y chromosome is associated with an increased risk of gonadoblastoma in TS women, although recent research suggests that hidden Y mosaicism may be more common than previously described, depending on the methods used. In our study, no tumors were found in the TS cohort, affirming the rarity of hidden Y mosaicism in females with TS.

Disclosures There is no conflict of interest to disclose.