A 19-year-old male was referred from the breast service with 9-month history of gynaecomastia. Investigations demonstrated an elevated total testosterone level (43.2nmol/L [RR9-30], and oestradiol (374pmol/L [RI<200]), suppressed gonadotrophin and elevated hCG levels (670IU/L [RI <3]). SHBG and AFP were normal. Patient reported use of gym supplements and had noted a 12kg weight gain in lean body mass. He denied use of exogenous hormones.

Examination findings included BMI 23kg/m2, muscular build and bilateral tender gynaecomastia. No testicular masses were found on examination or ultrasound. CT abdomen demonstrated borderline retroperitoneal nodes of uncertain significance. FDG-PET revealed bulky markedly hypermetabolic palatine tonsils and nasopharyngeal mucosal space with bilateral cervical adenopathy. He proceeded to tonsillectomy which demonstrated lymphoid hyperplasia.

Despite resection, the biochemical changes persisted. Further review of PET scan raised the suspicion of prominent duodenal area with greater than expected for physiological uptake. Interval imaging demonstrated growth of this node and hCG rose to 5550IU/L. The testes remained normal. A presumptive diagnosis and treatment plan was reached via MDM discussions. Chemotherapy treatment was initiated. This was followed by normalisation of hormonal and tumour markers along with resolution symptomology. A persistently enlarged node was resected following completion of treatment and demonstrated a hCG staining necrotic tumour.

This case posed challenges along the way and could even be unnerving to any clinician, particularly in light of a lack of a preliminary tissue diagnosis with a progressively elevating hCG level. In the end it required MDM discussions to reach a presumptive diagnosis and treatment plan. This case aims to demonstrate that gynecomastia would be a very rare consequence of metastatic disease with spontaneous regression of primary tumour.