RT Book, Section A1 Varadhachary, Gauri R. A1 Abbruzzese, James L. A2 Jameson, J. Larry A2 Fauci, Anthony S. A2 Kasper, Dennis L. A2 Hauser, Stephen L. A2 Longo, Dan L. A2 Loscalzo, Joseph SR Print(0) ID 1160012087 T1 Carcinoma of Unknown Primary T2 Harrison's Principles of Internal Medicine, 20e YR 2018 FD 2018 PB McGraw-Hill Education PP New York, NY SN 9781259644016 LK accesspharmacy.mhmedical.com/content.aspx?aid=1160012087 RD 2024/03/29 AB Carcinoma of unknown primary (CUP) is a biopsy-proven malignancy for which the anatomic site of origin remains unidentified after a focused search. CUP is one of the 10 most frequently diagnosed cancers worldwide, accounting for 3–5% of all cancers. Most investigators limit CUP to epithelial and undifferentiated cancers and do not include lymphomas, metastatic melanomas, and metastatic sarcomas because these cancers have specific histology- and stage-based treatments that guide management even in the absence of a primary cancer.