Rosettes in actinic keratosis and squamous cell carcinoma: distribution, association to other dermoscopic signs and description of the rosette pattern

Background Rosettes, a dermoscopic structure characterized by four white points arranged as a 4‐leaf clover, supports the dermoscopic diagnosis of actinic keratosis ( AK ) or squamous cell carcinoma ( SCC ). Objective The association of rosettes with other dermoscopic structures in AK or SCC and their distribution has not been analysed yet. Methods We conducted a prospective study of patients with histologically proven AK or SCC who presented dermoscopic rosettes at initial evaluation. Results A total of 56 tumours were collected (94.6% AK and 5.4% SCC ). Thirty‐seven (66.1%) lesions were non‐pigmented and 19 (33.9%) pigmented. The most common dermoscopic findings were erythema (53; 94.6%) and scale (42; 75%). White circles were present in 21 lesions (37.5%); pigmented pseudonetwork in 18 (32.1%) and multiple grey to brown dots and globules in 14 (25%). Rosettes were distributed focally in 9 (16.1%) and generalized in 47 (83.9%). The rosette pattern (rosettes as the main structure) was observed only in AK (19; 35.8%). Limitations The analysis was not blinded. The distinction between focal distribution (up to 3 rosettes) or generalized could be considered arbitrary. Conclusion The rosette pattern identified in AK may be a specific pattern for AK .