ESPE Abstracts

Background: GnRH-independent precocious puberty with elevated β-human chorionic gonadotropin (β-HCG) levels can be the presenting sign of secreting germ cell tumor (GCT) in boys. These tumors are very rare, but have a higher incidence rate in Klinefelter syndrome.

Case presentation: Here we report a case of a 7.3 year-old boy presenting with precocious puberty. In his physical examination, his height was 143.0 cm (SDS 3.32) and weight 38.5 kg (SDS 2.36). He had a testicular volume (TV) of 8-10 ml bilaterally and stage of puberty according to Tanner of A1 and P3. Biochemical findings revealed suppressed gonadotropins, raised testosterone levels, and elevated β-HCG levels of 105 mIU/ml (normal <5 mIU/ml). The LHRH test revealed a suppression of the gonadotropins with only a minimal increase in the LH level during the test (peak LH level 1.08 mIU/ml). ACTH stimulation test showed normal levels of cortisol and 17-OH progesterone (17-OHP). The skeletal age was markedly accelerated (12 years). Imaging scans including chest X ray, whole body CT, brain MRI and testicular US were normal with the exception of a small pineal cyst. Bone scan was normal, with no evidence of fibrous dysplasia. After two weeks of his initial presentations, the levels of β-HCG returned to normal (1 mIU/ml). The β-HCG levels in the cerebrospinal fluid were also within the normal range, measuring less than 1 mIU/ml. Throughout the follow-up period, the β-HCG levels showed fluctuations ranging from 1 to 105 mIU/ml. A karyotype test was performed and confirmed the presence of Klinefelter syndrome. After continuous monitoring for 10 months, when the β-HCG levels reached 3.6 mIU/ml, a PET-CT scan detected the existence of a hypodense lesion measuring 37X21X24 mm with calcifications and macroscopic fat tissue. Subsequently, the patient underwent tumor resection, and the histopathological examination revealed an intrathymic mature cystic teratoma.

Discussion: In this case, we present a challenging diagnosis of a mediastinal germ cell tumor in a 7.3-year-old boy. This case emphasizes the significance of performing karyotype testing in boys who exhibit precocious puberty and elevated β-HCG levels and highlights the need for continued monitoring and repeated imaging, even in cases where β-HCG levels decrease spontaneously and remain relatively low.