title: Malignant changes in a giant orbital keratoacanthoma developing over 25 years.
abstract: OBJECTIVE
  To report a patient with a history over 25 years of a slowly growing, large, invasive crateriform tumour filling the anterior part of the orbit.
  
  
  METHODS
  A 61-year-old male presented with a large tumour of the left orbit. Exenteration was performed with subsequent histological analysis of the excised mass.
  
  
  RESULTS
  The main tumour showed the characteristic features of a keratoacanthoma. However, the posterior aspect of the tumour disclosed the morphology of a squamous cell carcinoma. Six months later, the patient presented with metastases to lymph nodes, lung and mediastinal tissue. A leukemoid reaction was diagnosed by fine needle biopsy.
  
  
  CONCLUSIONS
  The giant variety of keratoacanthoma may fail to regress and can transform into a squamous cell carcinoma. In our patient, the development of a chronic lymphoid leukemia raises the possibility that it may be the underlying cause for the transformation of the posterior part of the keratoacanthoma into a frank squamous cell carcinoma.
authors.affiliation: Eye Pathology Institute, University of Copenhagen, Denmark.
authors.forename: G A
authors.initials: GA
authors.lastname: Alyahya
authors.forename: S
authors.initials: S
authors.lastname: Heegaard
authors.forename: J U
authors.initials: JU
authors.lastname: Prause
mesh_terms: D002294:Carcinoma, Squamous Cell / Q000473:pathology* / Q000556:secondary; D002471:Cell Transformation, Neoplastic / Q000473:pathology*; D017809:Fatal Outcome; D006801:Humans; D007636:Keratoacanthoma / Q000000981:diagnostic imaging / Q000473:pathology*; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000473:pathology*; D008175:Lung Neoplasms / Q000556:secondary; D008207:Lymphatic Metastasis; D008297:Male; D008479:Mediastinal Neoplasms / Q000556:secondary; D008875:Middle Aged; D009916:Orbital Diseases / Q000000981:diagnostic imaging / Q000473:pathology*; D009918:Orbital Neoplasms / Q000473:pathology*; D014057:Tomography, X-Ray Computed