No retraction artifact; no to rare mitotic activity
Top Differential Diagnoses
• DDx of nevus sebaceus
Epidermal nevus: Lacks abnormalities of follicles and sweat glands
Sebaceous adenoma: Lacks epidermal acanthosis and follicular structures
Sebaceous hyperplasia: Mature follicles without epidermal changes
• DDx of basaloid follicular hamartoma
BCC: More cytologic atypia, retraction spaces, inflammatory stroma, mitotic activity
Nevus Sebaceus Nevus sebaceus has an acanthotic epidermis, often with a papillomatous surface . The follicles have a disorganized appearance , and there are often associated large sebaceous glands .
Basaloid Follicular Hamartoma Basaloid follicular hamartoma is characterized by multifocal islands of basaloid epithelium resembling primitive follicles that are surrounded by a fibroblastic stroma.
Nevus Sebaceus at Low Magnification This nevus sebaceus demonstrates a papillomatous acanthotic epidermis overlying disorganized follicles with prominent sebaceous glands .
Immature Follicles in Nevus Sebaceus In this nevus sebaceus from a young child, there are disorganized, immature follicles ; sebaceous glands are not prominent in this view but are often hypoplastic before puberty.
TERMINOLOGY
Synonyms
• Nevus sebaceus: Organoid nevus, Jadassohn nevus
Definitions
• Nevus sebaceus
Hamartoma with abnormalities of epidermis, follicles, sebaceous glands, and apocrine glands
• Basaloid follicular hamartoma
Hamartoma resembling primitive follicles
ETIOLOGY/PATHOGENESIS
Developmental Anomaly
• Nevus sebaceus
Deletion of PTCH1 (PTCH) gene may play role
• Basaloid follicular hamartoma
Possible role for Sonic Hedgehog signaling pathway
CLINICAL ISSUES
Presentation
• Nevus sebaceus
Usually presents in infancy, often at birth; often enlarges during puberty
Usually involves scalp, less commonly on face, as yellowish flat to warty plaque
• Follicular hamartomas
Solitary
– Elderly patients with flesh-colored papule on face
– May clinically mimic basal cell carcinoma (BCC)
Localized
– Presents in 3rd-4th decade on head as erythematous to hyperpigmented plaque
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. The follicles have a disorganized appearance 
, and there are often associated large sebaceous glands 
.
resembling primitive follicles that are surrounded by a fibroblastic stroma.
overlying disorganized follicles with prominent sebaceous glands 
.
; sebaceous glands are not prominent in this view but are often hypoplastic before puberty.
