Keratoacanthoma
Keratoacanthoma is a common, rapidly growing squamoproliferative tumour that may spontaneously regress. It is histologically indistinguishable from (and likely a variant of) well-differentiated cutaneous invasive squamous cell carcinoma, with distinct clinical behavior.
Melanocytic Naevus
Junctional, compound, and dermal naevi are benign localized neoplastic proliferations of naevus cells (a type of melanocyte). Like all melanocytic naevi, these lesions are defined by the presence of nests of melanocytes.
Lichenoid keratosis
Lichen planus—like keratosis is a benign squamoproliferative lesion showing chronic inflammation and interface changes (likely representing active regression).
Solar Keratosis (Actinic Keratosis)
Actinic keratosis (AK) is an intraepithelial neoplastic lesion that may progress into invasive squamous cell carcinoma (SCC) or may spontaneously regress.
Dermatofibroma
Dermatofibroma (fibrous histiocytoma) is a common benign papular or nodular skin lesion composed of variable combinations of fibroblastic cells, macrophages, and coarse collagen.
Squamous cell carcinoma (SCC)
Cutaneous squamous cell carcinoma (SCC) is a malignancy of epidermal keratinocytes that exhibits various degrees of differentiation that partially recapitulate the cytology of squamous cells of the epidermal stratum spinosum. The lesions can be in situ or invasive with the potential for metastasis.