Cancer of unknown primary origin overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: ; Roukoz A. Karam, M.D.[2]
Overview
Cancer of unknown primary origin or CUP is the diagnosis of metastatic cancer when the anatomic site of origin remains unidentified. Cancer of unknown primary origin is common, and it accounts for 2–5% of all cancers. Cancer of unknown primary origin may be classified according to pathology findings into 4 groups: adenocarcinomas, poorly differentiated carcinomas, squamous cell carcinomas, and carcinomas with neuroendocrine differentiation. The majority of patients with cancer of unknown primary origin may be initially asymptomatic. Early clinical features include fatigue, weight-loss, and loss of appetite. If left untreated, the majority of patients with cancer of unknown primary origin may progress to develop multiple organ failure, heart failure, and death. The treatment for cancer of unknown primary origin will depend on several factors, such as: metastatic origin, biopsy findings, patients age, and performance status. The 5-year survival of patients with cancer of unknown primary origin is less than 2%.
Historical Perspective
Cancer of unknown primary origin was first discovered in the 1980s and was based solely on imaging studies.
Classification
Cancer of unknown primary origin may be classified based on light microscopy of the tissue biopsy into 4 groups including adenocarcinomas, squamous cell carcinomas, poorly differentiated tumors, and carcinomas with neuroendocrine differentiation.
Pathophysiology
The exact pathogenesis of cancer of unknown primary origin is not fully understood. Cancer of unknown primary, like other cancers, arises from one cell that has managed to escape regulation and produces a tumor at a certain site (the site of origin) and consequently metastasizes to other parts of the body.