Benign Keratinocytic Acanthomas and Proliferations

Abstract

Acanthomas are benign proliferations of keratinocytes. Histological features include acanthosis, hyperkeratosis, dyskeratosis and acantholysis. Seborrhoeic keratosis is very common, appears in mid‐life and affects the majority of older adults. Clinical and dermoscopic features are characteristic. Certain somatic mutations are common, but the lesions are genetically stable and not premalignant. Surgery and cryotherapy are effective. Stucco keratosis is a variant in which white hyperkeratotic papules occur on the limbs in older adults. The dermatosis papulosa nigra variant occurs mostly in pigmented skin on the face. Warty dyskeratoma is rare and presents as a cup‐shaped nodule with a keratotic plug with dyskeratosis and acantholysis. Clear cell acanthoma is a red, dome‐shaped papule often on a lower limb with glycogen‐containing cells. Lichenoid keratosis is a solitary pink or brown plaque, mimicking other lesions. Pseudoepitheliomatous hyperplasia is a reactive epidermal proliferation occurring secondary to inflammatory or neoplastic conditions that mimics squamous cell carcinoma.