and electron microscopic studies may be helpful. Special stains can be applied to the tissue slides to help in diagnosis. The problem is more significant in poorly differentiated tumors, since well-differentiated tumors tend to resemble the tissue of origin and the pathologist can often suggest the likely diagnosis. With poorly differentiated tumors the diagnosis is more uncertain.
Diagnosis and Staging If possible, biopsy is delayed until studies have tried to find the primary site. These studies include examination of head and neck areas directly and with mirrors and scopes. Suspicious areas are biopsied. If there are no suspicious areas, random biopsies are done of the nasopharynx , base of the tongue and the pyriform sinus on the same side as the neck lesion . If the tonsil is not present, a biopsy is done where the tonsil used to be. If the tonsil is present, it should be biopsied or removed. Sinus x-rays are often done and any abnormality is also biopsied. Other studies include MRI and CT scans.
Staging systems have been described, but of course the "T" classification has no relevance, since the primary tumor has not been found. Three-year local control and survival rates for squamous cancers involving the lymph nodes of the neck, with unknown primary tumor, following surgery and/or radiotherapy , are:
N1 (single node smaller than 3 cm/ 1¬Ω in., one side)...............40 to 50 percent
N2 (nodes 3 - cm/1¼ -2½ in., one side)............................................38 percent
N3 (larger nodes, either or both sides)..............................................26 percent
