title: Comparison of risk factors of single Basal cell carcinoma with multiple Basal cell carcinomas.
abstract: BACKGROUND
  Basal cell carcinoma (BCC) is the most common malignant skin tumor. Although mortality attributable to BCC is not high, the disease is responsible for considerable morbidity. There is evidence that the number of patients who develop more than one BCC is increasing.
  
  
  OBJECTIVE
  The aim of this study was to elucidate possible risk factors for developing Multiple BCC.
  
  
  METHODS
  Patients with histologically proven BCC (n = 218) were divided into two groups (single BCC and Multiple BCC) according to the number of their tumors and their profile were reviewed. Probable risk factors were compared between these two groups.
  
  
  RESULTS
  Among 33 evaluated risk factors, mountainous area of birth, past history of BCC, history of radiotherapy (in childhood due to tinea capitis), abnormal underlying skin at the site of tumor, and pigmented pathologic type showed significant differences between the two groups.
  
  
  CONCLUSIONS
  The high rate of additional occurrences of skin cancers among patients with previously diagnosed BCC emphasizes the need of continued follow-up of these individuals. Those with higher risk require closest screening.
authors.affiliation: Department of Dermatology, Razi Hospital, Tehran University of Medical Sciences, Tehran, Iran .
authors.forename: Zahra
authors.initials: Z
authors.lastname: Hallaji
authors.forename: Hoda
authors.initials: H
authors.lastname: Rahimi
authors.forename: Mostafa
authors.initials: M
authors.lastname: Mirshams-Shahshahani