Dermatomyositis With Carcinoma of Unknown Primary Disease in the Head and Neck Diagnosed by Muscle Biopsy During Neck Dissection

Dermatomyositis is an idiopathic inflammatory myopathy that can occur with a cutaneous eruption, worsening muscle weakness, and sometimes dysphagia. In addition, as is widely known, dermatomyositis is associated with malignant tumors in some patients.¹ Although diagnosis of dermatomyositis is based on a combination of clinical symptoms and various tests, muscle biopsy remains the standard in the diagnosis of dermatomyositis in spite of its invasiveness.² This report describes a unique case of dermatomyositis with carcinoma of unknown primary disease in the head and neck (CUPHN) in which neck dissection was a preceding treatment for CUPHN. During the neck dissection, we performed a muscle biopsy of the cervical muscles and made a definitive diagnosis of dermatomyositis.