الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
The definition of metastases of unknown origin (MUO) includes patients who present with histologically confirmed metastatic cancer in whom a detailed medical history, complete physical examination including pelvic and rectal examination, full blood count and biochemistry, urine analysis and stool occult blood testing, histopathological review of biopsy material with the use of immunohistochemistry, chest radiography, computed tomography (CT) of the abdomen and pelvis and, in certain cases, mammography fail to identify the primary site. Cancers of the unknown primary are categorized into four major subtypes by routine light microscopy criteria: (a) adenocarcinomas: well and moderately differentiated, (b) undifferentiated or poorly differentiated adenocarcinomas, (c) squamous cell carcinomas and (d) undifferentiated neoplasms. The characteristic clinical features of MUO include the following: - a short history of local symptoms e.g.; pain, swelling, and cough that are related to site of metastases, brief history of constitutional symptoms e.g., weight loss, malaise, fatigue and fever, often related to hepatic metastases, obvious abnormalities on physical examination, such as palpable masses at a single site, or, more frequently, at multiple sites and the possible presence of paraneoplastic syndromes e.g., superficial migratory thrombophlebitis; hypercalcemia; neurologic dysfunction. Clinical localization includes several investigations to evaluate MUO. It includes tumor markers e.g.: prostatic specific antigen and alpha feto protein, imaging procedures e.g.: CT and MRI and endoscopes e.g.: bronchoscopy. Histopathological examination is the corner stone for investigation of MUO. It includes light microscopic examination , immunohistochemical examination, electron microscopic examination and molecular cytogeneics. The most common sites of metastases of unknown origin are lymph nodes including mediastinal, axillary, cervical and inguinal nodes , liver which represent about 25% of all MUO, bone as multiple leision or single metastatic site, brain and lungs with parenchymal metastases or isolated malignant pleural effusion. Despite extensive work-up, less than 20% of patients with MUO have a primary site of their cancer identified antemortem.