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.