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Updated: Jan 21, 2026

Ex Vivo Treatment Response of Primary Tumors and/or Associated Metastases for Preclinical and Clinical Development of Therapeutics
Published on: October 2, 2014
Metastases with definitive pathological diagnosis but no detectable primary tumor: A surveillance epidemiology and
Lianyuan Tao1, Haibo Yu1, Yadong Dong1
1Department of Hepatobiliary Surgery, Henan Provincial People's Hospital, People's Hospital of Zhengzhou University, School of Clinical Medicine, Henan University, Zhengzhou, China.
Background:
This study investigates the characteristics of a special type of cancer of unknown primary site (CUP, type 2), which is a metastasis of a definite pathological diagnosis without a detectable primary site.
Patients And Methods:
Patients diagnosed between 2004 and 2014 were identified from the Surveillance Epidemiology and End Results (SEER) database. The characteristics of type 2 CUP from different sources were analyzed. For each source of type 2 CUP, tumors of the corresponding Tn N0-X M1 stage were used as controls.
Results:
A total of 8505 patients with type 2 CUP were included in this analysis. Type 2 CUP shows an increasing trend, while type 1 shows the opposite. Type 2 CUPs have significant differences with stage IV of the same pathological primary lesion. Many characteristics influenced the prognosis of type 2 CUP patients, including marital status, age, race, sex, registration time, lymph node metastasis, surgery, chemotherapy, and radiation.
Conclusion:
Our study suggests that identifying the source of metastasis is the key to the selection of treatment and the determination of the prognosis for CUP.
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