Nose, Actinic keratosis

Nasal cutaneous horn, also called cornu cutaneum, presents as a solitary painless hard-yellow cutaneous lesion extending upward from the skin up to several centimeters. It occurs in areas exposed to sun damage and UV radiation such as the head, neck, and hands of elderly patients. The most commonly accociated underlying etiology is actinic keratosis. Other common etiologies include squamous cell carcinoma, verruca, and seborrheic keratosis.

This case shows histological features of a hyperkeratotic lesion with thickened stratum corneum and low-grade actinic keratosis consisting of atypical keratinocytes with pleomorphic and hyperchromatic nuclei in the basilar portion of the epidermis.