Piriform sinus carcinoma with a paraneoplastic syndrome misdiagnosed as adult onset Still's disease: a case report.

Paraneoplastic syndromes (PS) occur less commonly in association with otolaryngologic neoplasms than other carcinomas such as those of lung or breast. Piriform sinus carcinoma with PS is extremely rare. We here report a case of piriform sinus carcinoma accompanied by PS that was initially misdiagnosed as adult onset Still's disease and describe our diagnosis and treatment. One lesson we have drawn from the experience of this misdiagnosis is that PS symptoms may manifest before the primary tumor is evident and complicate the diagnostic process.