Histology A distinguishing feature of<unk>  is the presence of large numbers of lipid-laden foamy histiocytes in the lesion, and essentially limited to, the connective tissue papillae in the lesion. The lesions are solitary, raised, or polypoid with cup-shaped craters filled with parakeratotic cells that blend into keratinocytes of an acanthotic and papillomatous epidermis. There is a neutrophilic infiltrate of varying intensity between plump parakeratotic cells and keratinocytes, near the surface of the epidermis. The xanthoma cells contain periodic acid Schiff positive, diastase resistant granules. The foam cells are monocyte-macrophage lineage with positive immunohistochemical markers for CD68 (KP1) and cathepsin B. Differential diagnosis Differential diagnosis includes seborrheic keratosis, verruca simplex, condyloma acuminatum, granular cell myoblastoma, vulvar intraepithelial neoplasia, bowenoid papulosis, erythroplasia of Queyrat, and verrucous carcinoma
Verruciform xanthoma
Pseudoxanthoma elasticum
Phakomatosis
Metachondromatosis
Keratoacanthoma
Linear and whorled nevoid hypermelanosis
Acanthoma fissuratum
Erythromelanosis follicularis faciei et colli