title: Unusual Dermoscopic Patterns of Seborrheic Keratosis.
abstract: BACKGROUND
  Seborrheic keratoses (SKs) may sometimes mimic benign and malignant skin tumors, and a biopsy can be necessary in order to rule out malignancy.
  
  
  METHODS
  From the database of our pigmented lesion clinic, we evaluated the dermoscopic features of difficult-to-diagnose SKs that were biopsied between January 2010 and December 2014.
  
  
  RESULTS
  SKs represented 3.8% of all excised lesions (161/ 4,182). Specifically, 91 (56.5%) were excised to rule out melanoma, 63 (39.1%) to rule out squamous cell carcinoma and 7 (4.4%) to rule out basal cell carcinoma. The following 10 global dermoscopic patterns were identified: multicomponent (32; 19.9%); reticular (24; 14.9%), characterized by an irregular pigment network; bowenoid (21; 13.0%); hairpin (19; 11.8%); keratoacanthoma-like (16; 9.9%); blue-nevus-like (15; 9.3%); lichenoid (6; 3.7%); hyperkeratotic (6; 3.7%); clonal (5; 3.1%); spitzoid (5; 3.1%). Furthermore, 12 SKs (7.5%) were not included in any of such patterns (not classified).
  
  
  CONCLUSIONS
  Our results are in line with previous studies highlighting the dermoscopic variability of SKs. Although excised SKs may be classified into 1 of 10 repetitive dermoscopic patterns, a biopsy remains mandatory for those that cannot be clearly differentiated from common skin malignancies.
authors.affiliation: Dermatology Unit, Second University of Naples, Naples, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Squillace
authors.forename: Milena
authors.initials: M
authors.lastname: Cappello
authors.forename: Caterina
authors.initials: C
authors.lastname: Longo
authors.forename: Elvira
authors.initials: E
authors.lastname: Moscarella
authors.forename: Roberto
authors.initials: R
authors.lastname: Alfano
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Argenziano
mesh_terms: D001706:Biopsy; D002280:Basal Cell Carcinoma / Q000175:diagnosis* / Q000473:pathology; D002294:Carcinoma, Squamous Cell / Q000175:diagnosis* / Q000473:pathology; D046169:Dermoscopy; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D017492:Keratosis, Seborrheic / Q000000981:diagnostic imaging* / Q000473:pathology; D008297:Male; D008545:Melanoma / Q000175:diagnosis* / Q000473:pathology; D008875:Middle Aged; D012867:Skin / Q000473:pathology; D012878:Skin Neoplasms / Q000175:diagnosis* / Q000473:pathology