Bilateral gynaecomastia as the sole presenting feature of a Y chromosome abnormality complicated by a gonadal tumour in an otherwise phenotypically normal male

We report the case of a 33-year-old male presenting with bilateral gynaecomastia whose karyotype was mosaic with 60% of the cells showing an isochromosome for the short arm of the Y chromosome and 40% showing 45,X complement. Further investigation revealed evidence of a stage one seminoma of the right testis and complete azoospermia. He was treated with bilateral orchidectomy and adjuvant radiotherapy and made an uneventful recovery. The case highlights the importance of cytogenetic investigation and appropriate testicular imaging in patients who present with Endocrine-Related Cancer (1998) 5 55-57 gynaecomastia. Issa et al.: Y chromosome abnormality presenting with gynaecomastia 56 and no Y chromosome and 60% of the cells showing a chromosome count of 46 with one normal X chromosome and an abnormal Y chromosome. The G-banding characteristics of the Y chromosome were consistent with it being a dicentric isochromosome resulting in duplication of the short arm of the Y chromosome and deletion of most of the long arm (Fig. 1). This interpretation was confirmed with fluorescent in situ hybridisation studies with a Y centromere specific probe, which showed two discrete areas of labelling separated by a short segment consisting of long arm material (Fig. 2). Ultrasound examination of the testes showed a 15 mm hyperechoic lesion typical of a malignant tumour, probably a seminoma, in the right testis. Semen analysis revealed complete azoospermia, and therefore the patient was referred for bilateral orchidectomy in view of the high risk of malignancy in the apparently normal left testis. Histological examination confirmed the diagnosis of a right testicular seminoma and the lack of spermatogenesis in both testes. Both testes showed scattered large atypical germ cells within tubules but no in situ germ cell tumour was seen. He made an uneventful recovery and was referred for prophylactic radiotherapy.