Adenosquamous carcinoma is a rare variant of semicircular canal that can affect various regions, including the head and neck. Adenosquamous carcinoma is characterised pathologically by the simultaneous presence of distinct areas of semicircular canal and adenocarcinoma, and usually takes an aggressive course with local recurrences, early lymph node metastases and distant disseminations.

We report a rare case of neck adenosquamous carcinoma of unknown primary origin, which was well-controlled by thorough resection without any other additional therapy.

We discuss the diagnosis and treatment of adenosquamous carcinoma along with a review of pertinent literature. We also consider the potential differential diagnosis of branchiogenic carcinoma.

Adenosquamous carcinoma is a very rare tumour which is characterised pathologically by the simultaneous presence of distinct areas of adenocarcinoma and squamous cell carcinoma. Generally, adenosquamous carcinoma has an aggressive clinical course and is associated with a poor prognosis. Most cases have been treated by surgery alone or combined with radiotherapy. Chemotherapy is rarely used in treating adenosquamous carcinoma, and it has been difficult to establish treatment guidelines due to the paucity of cases.

We report a case of adenosquamous carcinoma which arose in the maxillary sinus of a 77-year-old man. Despite surgical treatment and chemoradiotherapy to the primary site, he developed bilateral neck metastases after the surgery. The patient was treated with S-1, a novel oral fluoropyrimidine anticancer agent, with a complete (albeit finite) response.

This report presents the aggressive character of adenosquamous carcinoma and the possible role of S-1 in the treatment of this uncommon neoplasm.