Rosettes in dermatology: A polarized perspective on diagnosis and clinical significance

Methodology

A systematic literature search was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.³ The search was performed in December 2024 across MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, and Web of Science. Keywords used included “rosettes,” “dermoscopy,” “polarized light,” “cutaneous neoplasms,” and “inflammatory skin diseases.” Studies published in English, reporting rosettes in various dermatological conditions, were included, while reviews, editorials, and non-English articles were excluded. Both observational and case-control studies were considered. Reference lists of relevant studies were manually searched for additional articles.

The search yielded 73 articles meeting the inclusion criteria, identifying 47 distinct diagnoses associated with rosettes. These conditions were categorized as neoplastic, inflammatory, infectious, and vascular.

Neoplastic conditions

Keratinizing neoplasms, such as actinic keratosis (AK) and squamous cell carcinoma (SCC), were most frequently reported, 19 of the 73 articles (26%) documenting rosettes in these lesions.⁴ Histopathologically, rosettes in these conditions correlate with corneal lamellae and areas of significant keratinization.⁵ Their presence can aid in distinguishing AK and SCC from other non-pigmented lesions, supporting early detection and timely intervention.

Additionally, rosettes have been noted in basal cell carcinoma and melanoma, albeit less frequently. In amelanotic melanoma, rosettes may serve as an early clue, assisting in differentiation from other non-pigmented malignancies.⁶

Inflammatory conditions

Discoid lupus erythematosus (DLE) was the most frequently reported inflammatory condition associated with rosettes, appearing alongside markers such as follicular plugs and telangiectasias.⁷ Their presence may help differentiate DLE from other chronic inflammatory dermatoses.

Rosettes have also been observed in plaque psoriasis, where they manifest as a generalized pattern rather than a focal finding.⁸ This feature may aid in distinguishing psoriasis from other erythematous scaly conditions like eczema and pityriasis rubra pilaris, guiding appropriate management strategies.

Infectious conditions

Molluscum contagiosum was the most reported infectious condition associated with rosettes, with three articles documenting their presence.⁹ The proposed mechanism involves keratinized debris within dilated follicles interacting with polarized light.

Rosettes have also been described in leishmaniasis and deep fungal infections, where they likely arise due to fibrotic changes and keratin deposition.¹⁰ Recognizing this pattern may assist clinicians in suspecting these infections and confirming the diagnosis with appropriate investigations such as histopathology, special stains, culture, or polymerase chain reaction.

Vascular conditions

Acroangiodermatitis was the sole vascular condition identified, with one article reporting rosettes in this context.¹¹ Although their presence in vascular conditions remains poorly understood, fibrosis and structural dermal changes may contribute to their formation.

Histopathological correlation

The exact histopathological basis of rosettes remains a subject of investigation. One prevailing hypothesis suggests that they result from polarized light interacting with keratin-filled adnexal openings or perifollicular fibrosis.¹² Histological examination frequently reveals compact orthokeratosis or parakeratosis with keratin-filled follicular infundibula as a potential structural basis.¹³ Table 1 demonstrates histopathological correlates of rosettes across disease categories. Further studies integrating high-resolution histological and dermoscopic correlation are needed to clarify these findings.

Clinical utility and future directions

While the presence of rosettes in various dermatological conditions has been previously documented, the exact clinical implications remain underexplored. Recognizing rosettes can assist in narrowing differential diagnoses and guiding biopsy decisions. For instance, their presence in AK and SCC supports these diagnoses, while their identification in inflammatory or infectious conditions like DLE or molluscum contagiosum provides additional diagnostic clues.¹⁴

While traditionally associated with actinic damage, rosettes have been reported in pediatric cases, particularly in congenital nevi, suggesting a broader clinical significance.¹⁵

Polarized light dermoscopy is essential for detecting rosettes, as their absence under non-polarized settings underscores their optical nature.¹⁶ The degree of polarization may influence visibility and clarity, warranting further research.

In conclusion, rosettes under dermoscopy are observed in a broad spectrum of dermatological conditions beyond keratinocytic neoplasms. Awareness of their diverse presentations can enhance diagnostic accuracy and inform clinical management. However, further studies are necessary to clarify their prognostic significance and potential implications in disease progression.