Localized, wart-like variants, solitary or multiple • Nevus unius lateris  Long, linear lesions on unilateral extremities • Ichthyosis hystrix  Large, bilateral lesions on trunk Etiology/Pathogenesis • Epidermal nevus syndrome includes neurological, ocular, and…

Juvenile XanthogranulomaThis is a typical appearance of a juvenile xanthogranuloma removed from the face of a small boy. The lesion is uniform and cellular and proliferates in the dermis with…

 Cystic areas resembling infundibulum with stratified squamous epithelium, granular layer, and basket-weave stratum corneum  Areas resembling internal and external root sheath  Foci of matrical epithelium  Areas resembling hair bulb with…

 Cells characteristically cluster around thin-walled capillaries • In postmenopausal patients, cells are more spindled, and overall cellularity is low • Mature adipose tissue component in minority of cases • Some cases show morphologic…

 Subset have brisk mitotic activity (> 5/10 HPF in 20%; > 10/10 HPF in 5%)  Atypical mitotic figures may be seen Ancillary Tests • Often positive for variety of nonspecific markers,…

 May be absent in late stage (regressed) lesions • Melanocytic markers may be useful to confirm presence of melanocytes • Spitzoid features may be present in some cases (halo Spitz nevi) • Reactive…

 Multicystic squamous neoplasm composed of mature keratinocytes lining keratin-filled spaces Etiology/Pathogenesis • Postulated that most cases arise in preexisting pilar (tricholemmal) cyst; may be related to chronic inflammation or trauma Clinical…

 PEH lacks nuclear atypia, tumor cell necrosis, and mitotic activity present in angiosarcoma • Hemangioma • PEH-like changes may occur in hemangiomas complicated by thrombosis • Arteriovenous malformation (AVM)  PEH-like changes may occur…

Large, Deep LymphangiomaClinical photograph shows a large, deep lymphangioma (cystic hygroma) on the lateral neck of a child. Superficial LymphangiomaThis example of a superficial lymphangioma shows widely dilated spaces in…

Chondroid Syringoma/Cutaneous Mixed Tumor Low MagnificationLow magnification shows a well-circumscribed tumor composed of epithelial islands with easily identifiable glandular/ductal structures embedded in a myxoid and hyaline stroma. Cutaneous Mixed Tumor…