Introduction and importance: Cancer of unknown primary site (CUP) is metastatic cancer without primary tumor found from comprehensive medical history, physical examination, and regular laboratory examination. Eighty percent of CUP include unfavorable groups with 3 to 6 months of median survival despite chemotherapy treatment.
Case presentation: A 52-year-old male was presented with a chief complaint of a recurrent lump in the neck and axilla. After comprehensive examinations over three years, the primary site of the metastatic tumor could not be found. Therefore, this patient was diagnosed with cancer of an unknown primary site.
Clinical discussion: In patient with CUP, more precise therapy can only begin when the exact form of cancer is identified. However, the delay in diagnosis would worsen the patient's condition, as treatment measures cannot be implemented.
Conclusion: Trimodal modalities including surgery, chemotherapy, and radiotherapy are suitable for CUP with squamous cell carcinoma proven in immunohistochemistry evaluation.
Keywords: Axilla dissection; Cancer of unknown primary site; Metastatic cancer; Radical neck dissection; Squamous cell carcinoma; Trimodal modalities.
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