A Case Report of a Cutaneous Mucinous Reaction Associated with Erlotinib Therapy Used in the Treatment of Metastatic Tonsillar Sinus Squamous Cell Carcinoma

Cutaneous mucinoses are a diverse group of diseases that are occasionally seen in the context of an adverse drug reaction. We report the case of a 59-year-old male who presented with an asymptomatic, acneiform rash on his forehead, scalp, nose, upper chest, and upper back that had developed after treatment with erlotinib therapy used in the treatment of metastatic tonsillar sinus squamous cell carcinoma. Biopsy of these lesions demonstrated atypical histology that had features of both follicular mucinosis and myxedema. This histologic phenomenon is a rare drug reaction that has not previously been described in association with erlotinib.