title: Metastatic cutaneous squamous cell carcinoma derived from actinic keratosis.
abstract: BACKGROUND
  Squamous cell carcinoma (SCC) with histologically contiguous actinic keratosis has long been thought of as a tumor with minimal risk for metastasis. The objective of this study was to determine if contiguous actinic keratosis is present in the original tumors of metastatic cutaneous SCC and to describe the histologic features of these tumors.
  
  
  METHODS
  The primary lesions of 22 patients with metastatic cutaneous SCC were examined using light microscopy.
  
  
  RESULTS
  Contiguous actinic keratosis was present histologically in 44% of the original lesions of cutaneous SCC that metastasized. The average tumor thickness was 6.6 mm. Greater than 66% of the tumors were well or moderately differentiated. The skin adjacent to the tumors showed solar degeneration in almost all instances.
  
  
  CONCLUSIONS
  The histologic presence of contiguous actinic keratosis is not a useful predictor of the metastatic behavior of cutaneous SCC. Increased tumor thickness and depth of invasion are the most consistent histopathologic features of cutaneous SCC that metastasize.
authors.affiliation: Department of Dermatology, University of Arkansas for Medical Sciences, Little Rock, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Dinehart
authors.forename: P
authors.initials: P
authors.lastname: Nelson-Adesokan
authors.forename: C
authors.initials: C
authors.lastname: Cockerell
authors.forename: S
authors.initials: S
authors.lastname: Russell
authors.forename: R
authors.initials: R
authors.lastname: Brown
mesh_terms: D002294:Carcinoma, Squamous Cell / Q000473:pathology*; D002454:Cell Differentiation; D006801:Humans; D007642:Keratosis / Q000473:pathology*; D008207:Lymphatic Metastasis; D009362:Neoplasm Metastasis; D011230:Precancerous Conditions / Q000473:pathology; D012878:Skin Neoplasms / Q000473:pathology*