Cetuximab Induced Hidrocystomas: A Case Report

Cetuximab is an epidermal growth factor receptor (EGFR) inhibitor that commonly results in follicular-based acneiform eruptions. EGFR is expressed in the epidermis, hair follicle epithelium, sweat gland apparatus, and plays an important role in the differentiation and development of the hair follicle. In this report we describe a 70-year-old man who developed an acneiform eruption on his nose, cheeks, neck, and back when cetuximab was started for metastatic colorectal carcinoma.  This initial eruption improved with cessation of cetuximab but left residual cystic papules on his nose and multiple superficial white cysts on his bilateral cheeks, neck and back. Skin biopsy of a representative lesion on the nose revealed a cyst-like cavity lined with epithelium similar to sweat glands within the dermis consistent with a hidrocystoma. In this case, it is plausible that the use of an EGFR inhibitor resulted in a cutaneous inflammatory reaction, that subsequently healed with blockage of the sweat duct apparatus causing the formation of cutaneous cysts, including both hidrocystomas and milia. Alternatively, the blockage of the duct may have resulted from inhibition of basal cell migration and increased cell adhesion within the eccrine gland causing accumulation of eccrine gland secretion, and eventually hidrocystomas. To our knowledge, this is the first case describing the resolution of a typical cetuximab-induced acneiform eruption with residual hidrocystomas and milia.