A disease in which cancerous cells are found in the squamous cells – thin, flat cells found in tissue that forms the surface of the skin, the lining of body organs and the passages of the respiratory and digestive tracts. Cancer can begin in the squamous cells and spread (metastasize) from its original site to the lymph nodes in the neck or around the collarbone. Lymph nodes are small bean-shaped structures that are found throughout the body. They produce and store infection-fighting cells. When the lymph nodes in the neck are found to contain squamous cell cancer, a doctor will try to find out where the cancer started (the primary tumor). If the doctor cannot find a primary tumor, the cancer is called a metastatic cancer with unseen (occult) primary.