• Reaction pattern in certain inflammatory conditions such as
Lichen planus
Lupus erythematosus
• Reaction pattern overlying certain infections
Particularly deep fungal
• Reaction pattern overlying tattoos
Particularly red pigment
Clinical Issues
• Variable presentation, depending upon underlying condition
• Excellent prognosis, no malignant potential
Microscopic
• Hyperplasia of epidermis
• Base of hyperplastic epidermis may show broad rete or jagged borders
• May seem to predominantly involve hair follicles and other adnexal structures
• Varying depth (but never into subcutis)
• Squamous eddies may be prominent
• Minimal keratinocyte atypia
Top Differential Diagnoses
• Squamous cell carcinoma
• Keratoacanthoma
• Hypertrophic lupus erythematosus
• Hypertrophic lichen planus
PEH Pseudoepitheliomatous hyperplasia (PEH) associated with a tattoo shows irregular downgrowth of the epidermis with bulbous rete . Black tattoo pigment and inflammation are present in the dermis.
PEH Associated With Tattoo Higher magnification of PEH associated with a tattoo shows prominent epidermal hyperplasia above black tattoo pigment deposits in the dermis.
PEH Associated With ALCL In this example of PEH associated with a primary cutaneous anaplastic large cell lymphoma (ALCL), the epithelium is obscured by atypical lymphocytes and eosinophils.
PEH at High Magnification Cytologic atypia is absent in PEH. There is parakeratosis , but a true squamous pearl is not evident.
TERMINOLOGY
Abbreviations
• Pseudoepitheliomatous hyperplasia (PEH)
Synonyms
• Pseudocarcinomatous hyperplasia
Definitions
• Florid proliferation of epidermis that mimics squamous cell carcinoma
• Reaction pattern that may be secondary to chronic irritation/trauma
ETIOLOGY/PATHOGENESIS
Associated or Underlying Conditions
• Tumors
e.g., granular cell tumor
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. Black tattoo pigment and inflammation are present in the dermis.
deposits in the dermis.
associated with a primary cutaneous anaplastic large cell lymphoma (ALCL), the epithelium is obscured by atypical lymphocytes 
and eosinophils.
, but a true squamous pearl is not evident.
