The relationship between the gain of X chromosome, the loss of Y chromosome and Trisomy 7 in Grade 4 Astrocytoma Tumours

A male in his early twenties, who was usually fit and well, underwent a biopsy of a brain tumour (WHO Grade 4 Astrocytoma) that revealed an XX biological sex chromosome pattern rather than the expected XY. The patient identified as male, denied prior hormonal treatment for gender reassignment and had no female sexual characteristics. The patient had a partial debulking of a large midline frontal tumour with Neurosurgery and was referred to Oncology. Further microarray genetics revealed a trisomy 7 pattern, which may be associated with mosaicism of sex chromosomes in brain tissue, including the loss of Y or gain of X. Interestingly, a ‘gain of X’ has not been explored as readily as the loss of Y alongside trisomy 7 and in the context of astrocytoma. We discuss the aetiopathogenesis, genetics and management of this rarity. The purpose of this article is to discuss the Loss of Y and gain of X in association with trisomy 7 and its relevance to an intracerebral tumour (Astrocytoma- WHO Grade 4) (29).