Table 1.

Main histological differential diagnoses of basal cell carcinoma (BCC).

Differential Diagnosis	Pathological Features
Tricoblastoma	Absence of cleft, rudimentary hair germs, papillary mesenchymal bodies.
ADC	Lack of basaloid cells disposed in peripheral palisades; adenoid-cystic lesion without connection to the epidermis; absence of artefactual clefts
MAC	Bland keratinocytes, keratin cysts, ductal differentiation CEA+, EMA+ and BerEp4-
Tricoepithelioma *	Rims of collagen bundles, calcification, follicular/sebaceous/infundibular differentiation and cut artefacts. Cytokeratin (CK)20+, p75+, Pleckstrin homology-like domain family A member 1 + (PHLDA1+), common acute lymphoblastic leukemiaantigen + (CD10+) in tumor stroma, CK 6-, Ki-67– and Androgen Rceptor - (AR-)
MCC	Cells arranged in a diffuse, trabecular and/or nested pattern, involving also the subcutis. Mouse Anti-Cytokeratin (CAM) 5.2+, CK20+, S100-, human leukocyte common antigen – ( LCA-), thyroid transcription factor 1- (TTF1-)

ADC: adenoid cystic carcinoma; MAC: microcystic adnexal carcinoma; MCC: Merkel cell carcinoma; * above all desmoplastic tricoepithelioma.