Unknown Primary Squamous Cell Carcinoma of the Head and Neck

Background: Squamous cell carcinoma metastatic to the neck from an unknown head and neck primary site is relatively uncommon and presents a challenging diagnostic and therapeutic dilemma. Methods: Review of the pertinent literature. Results: Diagnostic evaluation includes fine needle aspirate of the neck mass, chest roentgenography, computed tomography, and/or magnetic resonance imaging of the head and neck, followed by panendoscopy and directed biopsies. Ipsilateral tonsillectomy is indicated unless there is no lymphoid tissue in the tonsillar fossa. The primary tumor will be detected in approximately 40% of patients; about 80% of cancers are located in the base of tongue or tonsillar fossa. Optimal treatment is controversial. Options include treatment of the neck alone or both sides of the neck and the potential head and neck primary sites. The latter approach is associated with better local-regional control. Therefore, patients with N1 disease without extracapsular extension may be treated with a neck dissection alone and followed closely as long as an open biopsy was not performed prior to surgery. Few patients meet these criteria. Those with more advanced disease and/or a violated neck receive radiotherapy (RT) to the oropharynx, nasopharynx, and both sides of the neck, followed by evaluation for a neck dissection. Patients with advanced N2 or N3 disease receive adjuvant chemotherapy concomitantly with RT. The 5-year survival rate is approximately 50% and is influenced by the extent of neck disease. Conclusions: Diagnostic evaluation identifies the primary site in about 40% of patients; the majority are in the tonsillar fossa or tongue base. Treatment depends on extent of disease and yields a 5-year survival rate of about 50%.