Laboratory practitioners working in oncology are increasingly involved in implementing genomic medicine, operating at the intersection of the laboratory and the clinic. This includes molecular diagnostic work and molecular testing to direct entry into molecular-based clinical trials and treatment decision-making based on molecular profiling. In this article, we draw on qualitative interviews with laboratory practitioners in the United Kingdom to explore the role of laboratory work in genomic cancer medicine, focusing on the handling of patient tissue and making of potentiality to guide patients' present and future care. With an increase in molecular testing to inform standard care and clinical trial participation, we show how practitioners "potentialized" the tissue by carefully negotiating what to test, how to test, and when. This included maximizing and managing small amounts of tissue in anticipation of possible future patient care. Tissue archives also took on new meaning, and potentiality, which practitioners negotiated alongside patient care. Potentiality was key to generating the "big" future of genomic medicine and also involved care work where the tissue emerged as an extension of the patient, as a form of "material patienthood," to secure present and future care for patients through their involvement in genomic medicine.
