Cancer of Unknown Primary,please help !

My father ,55 years old, found by himself a enlarged lymph node in his left neck one month ago.He feels well without any active systemic or localizing symptoms . His past medical history was  negative.
On physical exam, there is a palpable firm nodes measuring 2-3 cm in the lower left cervical The remainder of his physical examination was negative.
Fine-needle aspiration (FNA) biopsy said metastatic squamous cancer.
Further workup included a computerized tomography (CT) scan of the chest, abdomen, and pelvis, which confirmed the left supraclavicular and also showed another enlarged lymph node (2-3cm) in the upper mediastinum. Ear, nose, and throat evaluation revealed no evident primary lesion on fiberoptic endoscopy.Upper and lower endoscopies of the gastrointestinal (GI) tract were negative.
Positron emission tomography (PET) scanning revealed uptake in the lower left neck, upper mediastinum, but nowhere else.
Would you please help me know what's most possible problem is? Is it lung caner? What's the possible treatment?
Is it possible lymphoma? What's the survival time for this lung caner? Sorry about so many questions, I'm really worried about my dad.

[Fernando Roque, MD]

Hi.  Cancer metastasis to the left cervical lymph node in a male most commonly comes from cancers of the head and neck or the lungs.  Lymphoma could also present with neck node lesions.  These areas have been extensively examined by CT, PET and endoscopy, and yet no primary lesion was located.  The next step is to do special stains (e.g. immunostaining) on the biopsy sample to help determine its tissue of origin.  However, the biopsy should be repeated, because immunostaining cannot be performed on an FNA sample (the amount of tissue is too small).  An excision biopsy of that cervical node should ideally be done.  Certain stains like cytokeratin and Leukocyte Common Antigen (LCA) can differentiate between lymphoma, head and neck or lung cancers.  

At this point, it may be premature to discuss survival and prognosis because these would really depend on what kind of cancer your father has.  I can understand your anxiety and concern, but for now, the best thing to do is to have those stains done and await the results, instead of speculating on what it might be.