Pseudoepitheliomatous Hyperplasia (PEH)

Compartment: Epidermis

Alt text: "Two-panel histologic comparison. Panel A shows pseudoepitheliomatous hyperplasia with bland, orderly epidermal downgrowths, normal cytology, and a normal mitotic figure. Panel B shows well-differentiated squamous cell carcinoma with cytologic atypia, pleomorphism, a dyskeratotic cell, an atypical mitotic figure, and an irregular keratin pearl."
Caption: “Pseudoepitheliomatous hyperplasia (A) versus well-differentiated squamous cell carcinoma (B): bland, orderly epidermal proliferation versus cytologically atypical, invasive growth.”

Definition: Reactive, exuberant proliferation of the epidermis that extends downward into the dermis.

Clinical Context: Granular cell tumor, Pemphigus vegetans, Deep fungal infection

Key Feature: Marked acanthosis with elongated, anastomosing rete ridges, bland cytology, and orderly maturation — lacking the atypia, dyskeratosis, and atypical mitoses of squamous cell carcinoma.

🔗 Related Terms: Acanthosis, Papillomatosis, Hyperkeratosis