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. 2014 Jan 29;8(3):261–268. doi: 10.1007/s12105-014-0522-z

Table 2.

Distinguishing features between CC and its important differential diagnoses

Microscopic
features
Carcinoma cuniculatum Verrucous carcinoma Conventional Squamous cell carcinoma Pseudoepitheliomatous hyperplasia
Architecture Well differentiated squamous lined keratin-filled, burrowing crypts Mixed exophytic and endophytic growth pattern. Verruciform exophytic component Solid, irregular nests/islands, squamous pearls may be present Markedly acanthotic irregular squamous epithelium
Invading front Deeply located cohesive squamous nests and cryptsa Broad “pushing” infiltration Aggressive stromal invasion with desmoplastic response Tongue-like projections of squamous epithelium. Absence of stromal desmoplasia
Lymphovascular invasion Not present Not present Possible Not present
Cytologic atypia Absent to mildb Absent to mildb Mild to severe Absent to mildb
Mitotic activity Variableb Variableb Frequent and atypical Variable, non atypical

aMay have superimposed pseudoepitheliomatous hyperplasia, displaying a reticulated network of tongue-like epithelial protrusions resulting in a jagged tumor–stromal interface mimicking aggressive stromal invasion

bThe degree of cytologic atypia and basally confined mitotic activity may be increased in acutely inflamed areas