Background: Primary retroperitoneal tumours (RPTs) encompass a wide range of diagnostic possibilities. Failure to recognise them appropriately may lead to suboptimal management, particularly in non-specialised centers. A structured diagnostic pathway is therefore essential to support appropriate treatment planning and timely referral to specialised teams.

Objective: To review key points of the diagnostic workup of primary RPTs, with special emphasis on those of mesenchymal origin.

Results: Primary RPTs represent a broad and heterogeneous group, with mesenchymal tumours accounting for approximately half of cases. Cross-sectional imaging plays a central role in the initial characterisation. Percutaneous core needle biopsy with histological and molecular analysis is recommended in most cases where imaging is not diagnostic. Serum tumour markers may provide valuable diagnostic clues in selected clinical settings.

Conclusion: Accurate diagnosis relies on a structured diagnostic pathway integrating imaging, biopsy when indicated and expert pathological review. Early referral to specialised multidisciplinary teams is essential to optimise management and improve oncologic outcomes.