Table 2: Clinicopathologic classification for cSCC*.

High risk behavior cSCC
 Bowen’s disease with invasion
 Adenosquamous carcinoma
 cSCC in proliferating pilar tumor/cysts
  Tricholemmal cysts
  Epidermoid cysts
 Desmoplastic cSCC
 De novo cSCC
 cSCC in chronic conditions
  Ulcers, sinus tracts, burns
  Osteomyelitis
  Chronic inflammatory disorders
 Radiation-induced cSCC
Indeterminate risk cSCC
 Clear cell SCC
 Signet ring cell
 Papillary cSCC
 Pigmented cSCC
 Follicular cSCC
 cSCC from benign adnexal cyst
Putative cSCC versus low grade cSCC
 Keratoacanthoma (KA)
  Not a bona fide cSCC
  Low grade behavior
   Giant KA,
   Subungual KA
   KA with Immunosuppression

*Modified Classification system from Cassarino et al. [24].