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Metastatic squamous cell cancer with unknown primary origin in the mediastinal lymph node

Metastatic tumors with unknown primary origin are a group of heterogeneous tumors with undetectable primary tumor site on admission. They have the common properties of rapid and aggressive progression and unpredictable metastases. They form 3%–5% of all cases with cancer and the fourth-most common cause of cancer-related deaths. The histological type of these tumors is commonly (90%) adenocarcinoma, whereas 5% are squamous cell carcinomas. Metastasis is observed in the liver, lungs, and bones. Mediastinal lymph node metastasis is extremely rare. They have a poor prognosis and the mean survival is shorter than a year. The case we have presented is a rare case due to its mediastinal lymph node involvement among tumors with unknown origin and squamous cell histological subtype.