Irritated seborrhoeic keratosis presenting as a cutaneous horn

Abstract

Seborrheic keratosis (SK) is a common benign cutaneous tumour that is frequently seen on the trunk, extremities, head and neck of geriatric population, and presents with a variety of clinical and histopathologic appearance.1 Malignant transformation of SK, although rare, appears to occur more particularly in irritated lesions of the elderly located on the head, neck and flexures.1 Premalignant skin lesions and malignant tumours reported to arise in SKs are basal cell carcinoma, Bowen's disease, keratoacanthoma, squamous cell carcinoma (SCC), adenocarcinoma, melanoma, eccrine porocarcinoma and ganglioneuroma.2-5 We describe herein a case with an irritated SK presenting as a cutaneous horn arising on her face. A 65-year-old woman presented with lesion on her left temporal area of 4 years’ duration. The mass had noticeably increased in size over several months and was accompanied by horn formation. Upon examination a dome-like yellow to black, polipoid greasy surfaced elevation with a horn formation of 2 × 5 cm in diamater was seen on the area (fig. 1). The histological appearances were consistent with irritated SK on excisional biopsy. As this lesion partly mimics SCC both clinically and histopathologically, we performed an immunohistochemical analysis of p53 and Ki-67 to see its growth potential. The percentage of p53 positive cells was > 50% in the specimen. Ki-67 reactivity was noted in the nucleus of basal or suprabasal region and the percentage of Ki-67 positive cells was 2.4%.