Beyond imaging: Cystic fluid tumour markers as a diagnostic aid in post-RPLND non-seminomatous germ cell tumour management

Objective: To assess the detection of tumour markers in the cyst fluid of residual cystic non-seminomatous germ cell tumours disease post chemotherapy at the time of retroperitoneal lymph node dissection (RPLND) and assess the correlation with pre-treatment serum markers. Materials and Methods: In this prospective study (May 2018–July 2023), cystic fluid was aspirated from residual masses during RPLND in 24 patients. Tumour markers alpha-fetoprotein (AFP), human chorionic gonadotropin (HCG), and lactate dehydrogenase (LDH) were measured and correlated with serum markers and histopathology. Results: Twenty-four out of 26 (92.3%) cystic teratoma cases showed elevated AFP, HCG, or both in cystic fluid despite normalised serum markers post chemotherapy. No significant correlation was observed between serum and cystic fluid marker levels. One benign case showed no detectable cystic markers. Cystic tumour marker levels were independent of primary testicular tumour histology. Conclusion: Cystic fluid tumour marker analysis at the time of post-chemotherapy RPLND frequently demonstrated elevated AFP and/or HCG in teratoma, even when serum markers were normal. There could be a role for assessment of cyst fluid tumour markers in patients with new cystic masses arising post RPLND to predict recurrence of teratoma. However, larger, multicentre studies including diverse cystic pathologies are needed to clarify the diagnostic accuracy and potential role of this approach in clinical decision-making. Level of Evidence: 2b