Table 3.

Histopathological differential diagnosis of Bowen’s disease

Disease	Differentiating feature
Actinic keratosis	Alternating pattern of parakeratosis and orthokeratosis
	Basal layer always involved
	Sparing of acrosyringia and acrotrichia
	No clear border - Diffuse transition into surrounding epidermis
	Less prominent mitotic figures
Bowenoid papulosis	Numerous mitosis in metaphase
	Small basophilic inclusions in cytoplasm of granular layer
	Koilocyte-like cells
Clonal seborrheic keratosis	Well-defined nests of cells in epidermis
	Nuclei appear small and darkly stained
	Intercellular bridges seen in only few areas
Hidracanthoma simplex	Exhibits “Jadassohn phenomenon” composed of bland basaloid cells
	Characteristic intracytoplasmic glycogen and occasional ductal structures
Invasive squamous cell carcinoma	Large islands of nests or islands of tumor cells expanding to deep dermis from overlying epidermis
	Tumor have pushing and expansile border
Intraepidermal Merkel cell carcinoma	Intraepidermal nests of merkel cells
	Stain positive for CK20, synaptophysin, chromogranin
Intraepidermal sebaceous carcinoma	Tumor composed of germinative, transitional, and mature sebaceous cells
Paget’s disease	Nest-like or glandular-like patterns with central-lumen abundant in basal layer
	No dyskeratosis
	Stain positive for carcinoembryonic antigen, mucin, Alcian blue, aldehyde fuchsin
	Periodic acid-Schiff positive and diastase resistant
	Overexpress cytokeratin 7 and gross cystic disease fluid protein 15 (GCDFP-15).
Pagetoid dyskeratosis	Scattered pale cells with small pyknotic nucleus
Pagetoid melanoma in-situ	Stains positive for S100 and/or Melan-A/MART 1
	Do not stain for cytokeratins
Podophyllin-induced wart changes	Absence of atypical cells and multinucleate giant cells
Trichilemmal carcinoma	Lobular aggregations of tumor cells
	Trichilemmal-type of keratinization
	Peripheral cell palisading of basaloid cells
	Glycogen deposition in cytoplasm of pale/clear cells