. 2020 Apr 6;11(13):3919–3931. doi: 10.7150/jca.42880

Table 4.

Comparison between metastatic cancer and CUP

Factors	Metastatic cancer	CUP
Source of the cancer	Always defined	Mainly never determined
Classification	it's named after the part of the body where it started	Cancer of unknown primary or occult primary cancer.
Primary organ	Known	Unknown
Staging system	TNM system is the most widely used; describes the size of the primary tumour, nearby involved lymph node, and distant metastasis.	No staging system exists for CUP, the staging depends on the histology of the cancer ⁹⁸.
Stage	Mainly stage IV	All CUPs are at least a stage II, and most of them are stage III or IV. Although the precise stage of the patient with CUP may not be known certain assumptions about the prognosis depending on which organs are impacted by cancer can still be made.
Type	Has the same type of cancer cells as the primary cancer	The origin unknown, mainly are epithelial cells; Adenocarcinoma.
Common organ	The lungs, liver, brain, and bones	Most of the times three or more organs are involved
Prognosis	Poor prognosis	Poor prognosis
Treatment	The best treatment for metastasis is the treatment of the primary cancer. Therapies may include chemotherapy or hormone therapy, immunotherapy, radiation therapy, surgery, or a combination of these.	Some treatments are standard (the currently used treatment), and some are being tested in clinical trials.
Survival	Better survival than CUP, except those with brain and respiratory metastases ¹⁵	Median overall survival of 3-9 months. The favourable prognostic group may have a median survival of nearly 36 months ¹⁵, ⁹⁹.