Crateriform Nodule over a Scar

Abstract

Keratoacanthoma is a low-grade epithelial neoplasm that originates from the pilosebaceous unit. The exact etiopathogenesis of keratoacanthoma is not known. It may arise secondary to other skin lesions such as psoriasis, herpes zoster, lichen planus. Clinically, it is characterized by rapidly growing, dome-shaped crateriform nodule with central keratotic core. The classic lesion shows rapid progression followed by spontaneous involution with a depressed, hypopigmented scar. Clinically differential diagnosis of keratoacanthoma includes squamous cell carcinoma, nodular basal cell carcinoma, nodular Kaposi sarcoma, and metastatic lesion to the skin. In contrast to these malignancies, keratoacanthoma undergo spontaneous resolution and it rarely spread through lymphatic, venous, or perineural routes. Surgical excision is the gold standard for the treatment of keratoacanthoma. Here, we describe a case of keratoacanthoma developing over a pre-existing scar following lichen planus hypertrophicus. High index of suspicion of keratoacanthoma is required while encountering rapidly growing nodule over a scar and histopathological examination is mandatory to rule out other malignancy.