Cancer of Unknown Primary: A Case Report on the Recognition of Its Clinical Entity and Standard of Care Management.

Cancer of unknown primary (CUP) is a distinct and well-established clinical entity that encompasses a heterogeneous group of histologically proven cancers that present unique diagnostic and therapeutic challenges. This case describes a male patient in his late 60s who presented with nonspecific gastrointestinal complaints. A comprehensive workup, including clinical evaluation and various biochemical, imaging, and invasive histopathologic tests, led to the diagnosis of CUP following consultation with medical oncology specialists. A decision was made to forgo further invasive molecular tissue sampling in search of a primary malignant process in favor of initiating systemic chemotherapy. The patient possessed an unfavorable set of prognostic signs. Rapid clinical deterioration occurred the day after treatment initiation. A goals of care conversation led to a transition towards comfort measures only care, and the patient ultimately passed away. This case highlights the importance of non-oncologically trained providers recognizing CUP as its own entity to facilitate standard of care management. Future research is needed to establish benefits in clinical trials looking at molecular tumor profiling and site-specific therapies for this rare malignancy.