Acknowledgements Development of the new Clinical Practice Guidelines for the Diag- nosis and Management of Melanoma was undertaken by Cancer Council Australia and Melanoma Institute Australia, and supported by the Skin Cancer College Australasia and the Australasian Col- lege of Dermatologists. The authors thank the staff of the Cancer Council Australia Clinical Guidelines Network for their invaluable guidance and support. In particular we thank Tamsin Curtis for coordinating the melanoma guidelines revision process and Cecilia Taing for undertaking the systematic literature review that provided the evidence on which this article was based. Reference 1. Cancer Council Australia Melanoma Guidelines Working Party. Clinical Practice Guidelines for the Diagnosis and Management of Melanoma. [Cited 17 Jul 2019.] Available from URL: https://wiki.cancer.org.au/ australia/Guidelines:Melanoma Michael A. Henderson,*† MD, FRACS John Spillane,*† MBBS, FRACS T. Michael Hughes,‡ MBBS (Hons), FRACS Andrew J. Spillane,§ MD, FRACS B. Mark Smithers,k MBBS, FRACS John F. Thompson,¶ MD, FRACS *Peter MacCallum Cancer Center, Melbourne, Victoria, Australia, †Department of Surgery, The University of Melbourne, Melbourne, Victoria, Australia, ‡Sydney Adventist Hospital, The University of Sydney, Sydney, New South Wales, Australia, §Melanoma Institute Australia, Royal North Shore Hospital, The University of Sydney, Sydney, New South Wales, Australia, ¶Queensland Melanoma Project, Princess Alexandra Hospital, The University of Queensland, Brisbane, Queensland, Australia and kMelanoma Institute Australia, The University of Sydney, Sydney, New South Wales, Australia doi: 10.1111/ans.15407 Organoids: the new kid in cancer research Cancer is a major health burden and is expected to rank as the lead- ing cause of death in every country in the 21st century. 1 Despite extensive research and advances in cancer care, there is significant limitation in translation of bench to bedside treatments, largely due to the nature of current cancer models used in research. Current cancer models include cell lines and mouse xenografts (PDXs). Cancer cell lines are two-dimensional models of cells grown in vitro. They have variable success in establishment, often undergo substantial in vitro genetic changes and fail to recapitulate the heterogeneity of the native tumour. Xenografts on the other hand retain the biology of the tumour better than cell lines. How- ever, they are expensive, time and resource intensive, have variable success in establishment and may develop mouse-specific tumour changes over time. 2 While both have been immensely useful in basic science, they have significant limitations in their clinical applicability. Recently, the development of a more physiological pre-clinical model that overcomes many of the deficiencies of cell lines and PDXs has come to the fore. Dubbed by Nature magazine as ‘the method of the year’, novel cancer models called ‘organoids’ have the potential to revolutionize cancer care. Organoids are three-dimensional (3D) cultures of cancer cells grown in the laboratory that recapitulate tumour heterogeneity and maintain genomic integrity far better than cell lines and animal models. Tumour-specific stem cells can grow from small pieces of tumour embedded in a synthetic extracellular matrix in a cell cul- ture plate with a cocktail of growth factors into self-organizing and self-sustaining 3D structures called organoids. 3 Organoids represent the native cancer in their mutations, physiology and their cellular interactions. These ‘mini tumours’ can be rapidly grown in a matter of days, with greater success rates than cell lines or mouse models. 4 Organoids have enormous clinical applicability and potentially rep- resent the next frontier in changing cancer care for patients. Organoids can be grown with high success rates from simple needle biopsies. To date, organoids have been successfully devel- oped from numerous cancers, including colorectal, pancreatic, gas- tric, oesophageal, liver, lung, glioblastomas and testicular cancers. 5 They can be used to develop a ‘living tumour biobank’ wherein replenishable organoids can be stored for each cancer. Organoids can be used to help predict and prognosticate patient responses to therapy. Early studies with rectal cancer have shown that organoids can help predict rectal cancer responses to chemoradiotherapy. 6 This could potentially change how we treat rectal cancer in the future. They can be used to model and study various diseases, from genetic disorders like cystic fibrosis to inflammatory conditions like Clostridium colitis. 7 The ability to also grow matched ‘normal’ tissue organoids allows one to interro- gate the genetic alterations that lead to cancer, with gene editing tools like CRISPR-Cas9 that can be used to switch genes on and off. 8 Immunotherapy has transformed the treatment landscape of can- cers such as melanoma and renal cell carcinoma. Currently, there are no reliable biomarkers to predict responses to immunotherapeu- tic drugs. Organoids provide a valuable strategy to evaluate the response to immunotherapy in patients, thereby selecting those likely to respond to immunotherapy, and avoiding immunotherapy related complications in non-responders. 9 One of the most promising areas for the utilization of organoids is in drug development and personalized medicine. Many drugs fail, or take years to reach the clinic due to regulations regarding evalua- tion of the drugs toxic profile. With the ability to grow normal Perspectives 1189 © 2019 Royal Australasian College of Surgeons