Table 5 Histological features of microcystic adnexal carcinoma and its differential diagnoses.

Microcystic adnexal carcinoma	The epidermis is usually not involved
	Poorly circumscribed
	Deep invasion into deep dermis and underlying tissues
	Depth greater than width
	Keratinous microcysts in superficial part
	Deeper areas with glandular and ductal differentiation
	Sclerotic stroma
	Cells are not pleomorphic
	Mitoses are rare to absent
	Perineural/intraneural involvement
	CEA and EMA highlight ductal structures
Syringoma	Well‐circumscribed strands of basaloid cells
	Confined to upper to mid dermis
	Well‐differentiated ductal/glandular structures
	“Tadpole” or “comma” shape
	Small horn cysts
	Width greater than depth
	Desmoplastic stroma
	No perineural involvement
Desmoplastic trichoepithelioma	Superficial
	Numerous small keratin cysts
	Foreign body reaction
	Calcification
	Lacks eccrine duct formation
	No perineural involvement
Sclerosing/morpheic basal cell carcinoma	Infiltrative basaloid cells
	Prominent sclerotic stroma
Papillary eccrine adenoma	Fairly well circumscribed
	Epithelial islands
	Glandular differentiation
	Luminal micropapillary projections
	Tumour stroma is fibrotic and frequently hyalinised

CEA, carcinoembryonic antigen; EMA, epithelial membrane antigen.