An exophytic and symptomatic lesion of the labial mucosa diagnosed as labial seborrheic keratosis.

Seborrheic keratosis is a common benign epidermal tumor that occurs mainly in the skin of the face and neck, trunk. The tumors are not, however, seen on the oral mucous membrane. Herein, we describe a case of labial seborrheic keratosis confirmed by histopathology. A healthy 63-year-old man was referred to our hospital for evaluation and treatment of a 2-month history of a labial mass with mild pain. Clinically, the initial impressions were malignant transformation of chronic discoid lupus erythematosus, syphilitic chancre, or keratoacanthoma. Surprisingly, our laboratory results and histopathologic evaluations established a novel diagnosis of a hyperkeratotic type of labial seborrheic keratosis (SK). This reminds us that atypical or varying features of seborrheic keratosis make it difficult to provide an accurate diagnosis. Clinical manifestations of some benign lesions may be misdiagnosed as malignancy. Consequently, dentists should consider this as a differential diagnosis in labial or other oral lesions.