Dermatology: Practical and Conceptual Research Letter | Dermatol Pract Concept. 2022;12(2):e2022069 1 Rosette or Four Dot Signs in Dermoscopy: a Non-specific Observation Rashmi Jindal1, Payal Chauhan1, Nadia Shirazi2 1 Department of Dermatology, Venereology & Leprosy, Himalayan Institute of Medical Sciences, Swami Rama Himalayan University, Dehradun, Uttarakhand, India 2 Department of Pathology, Himalayan Institute of Medical Sciences, Swami Rama Himalayan University, Dehradun, Uttarakhand, India Key words: dermoscopy, four dot, actinic keratosis, lichen planus, perniosis, lichen sclerosus et atrophicus Citation: Jindal R, Chauhan P, Shirazi N. Rosette/ four dot sign in dermoscopy: A non-specific observation. Dermatol Pract Concept. 2022;12(2):e2022069. DOI: https://doi.org/10.5826/dpc.1202a69 Accepted: October 6, 2021; Published: April 2022 Copyright: ©2022 Jindal et al. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (BY-NC-4.0), https://creativecommons.org/licenses/by-nc/4.0/, which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original authors and source are credited. Funding: None. Competing interests: None. Authorship: All authors have contributed significantly to this publication. Corresponding author: Dr Rashmi Jindal, Professor, Department of Dermatology, Venereology & Leprosy, Himalayan Institute of Medical Sciences, Swami Ram Nagar, Doiwala, Dehradun, Uttarakhand, India. E-mail: rashmijindal98@gmail.com Introduction Rosettes or four dot signs in dermoscopy are described as 4 bright white dots or globules grouped like a four-leaf clover. They vary in size from 0.2 mm to 0.5 mm and can be ori- ented in the same angulation or different angulation. These have been characteristically described in squamous cell car- cinoma and actinic keratosis [1]. However, there have been anecdotal reports of their presence in melanoma, basal cell carcinoma, dermatofibroma, molluscum contagiosum, lichen planus like keratosis, discoid lupus erythematosus, and pig- mented purpuric dermatoses [2]. Their definite histopatho- logical correlate has not been elucidated. The explanation accepted by most clinicians is that they represent the opti- cal effect between polarized light and follicular structures. Polarizing horny material at the infundibular level in ad- nexal openings and peri-follicular fibrosis results in smaller and larger rosettes, respectively. Case Presentation The present case series describes 5 diseases (in 5 patients) where rosettes were seen, suggesting that they would be non-specific. These were lichen sclerosus, lichen planus, per- niosis, apocrine hidrocystoma, and photo contact dermatitis (Figures 1-5). Diagnoses were confirmed histopathologically, and a possible dermoscopy correlation with observed histo- pathology was established (Table 1). Conclusions Rosette sign in dermoscopy is not disease-specific as was once presumed. Although it is observed in high frequency in actinic tumors like actinic keratosis and squamous cell carcinoma, several unrelated inflammatory and papulosquamous diseases also exhibit it. Its most likely explanation is the interaction of keratin filled adnexal openings with the polarized light. 2 Research Letter | Dermatol Pract Concept. 2022;12(2):e2022069 Figure 1. (A) Multiple white rosettes (blue circle, Dermlite DL200 hybrid, 10x magnification [3Gen]. (B) Multiple white atrophic plaques over leg. (C) Hyperkeratosis, epidermal atrophy with basal vacuolar degeneration, papillary dermal edema and underlying lymphocytic infiltrate (H&E, ×10). Figure 2. (A) Multiple white rosettes (blue circle). (B) Erythematous to violaceous plaques over trunk and extremities. (C) Hyperkeratosis with keratin filled craters, basal vacuolar degeneration and dense band like lymphocytic infiltrate at dermo-epidermal junction (H&E, ×10). Figure 3. (A) White rosettes (blue circle). (B) Erythema and edema over toes. (C) Hyperkeratosis, follicular plugging, dermal edema and perivascular as well as peri-eccrine lymphocytic infiltrate (H&E, ×10). Research Letter | Dermatol Pract Concept. 2022;12(2):e2022069 3 Table 1. Demographic profile, clinical features, and dermoscopy-histopathology correlation in 5 cases with rosette sign. Figure (Case) # Age (years)/ Gender Clinical presentation Duration Histopathological diagnosis Dermoscopy correlation with histopathology for rosettes #1 18/male Multiple white atrophic plaques over left leg 2 years Lichen sclerosus et atrophicus Follicular plugging #2 22/ female Multiple, itchy erythematous to violaceous plaques over trunk and extremities 2 months Lichen planus Hyperkeratosis with sharp depressions giving the appearance of keratin filled craters #3 20/ female Erythema and edema over toes 4 days Perniosis Hyperkeratosis with wavy margin and peri-eccrine inflammation #4 30/ male Skin-colored to bluish nodules coalescing to form a plaque over the neck 10 years Apocrine hidrocystoma Hyperkeratosis with follicular plugging and peri-follicular fibrosis #5 60/ male Bright red plaques over dorsae of hands 7 days Photo-contact dermatitis Parakeratotis scale filling the sweat duct openings. Figure 4. (A) Multiple white rosettes (blue circle). (B) Skin colored to bluish nodules coalescing to form a plaque over the neck. (C) Hyperkeratosis, follicular plugging with peri-follicular fibrosis, multiple dermal cystic spaces lined by a bilaminar epithelium with apocrine snouts at places (H&E, ×10). Figure 5. (A) White rosettes (blue circle). (B) Bright red plaques over dorsae of hands. (C) Parakeatosis with follicular plugging, spongiosis, dermal edema and peri-vascular lymphocytic infiltrate (H&E, ×10). 4 Research Letter | Dermatol Pract Concept. 2022;12(2):e2022069 References 1. Valdés-Morales KL, Peralta-Pedrero ML, Cruz FJ, Morales-Sán- chez MA. Diagnostic Accuracy of Dermoscopy of Actinic Keratosis: A Systematic Review. Dermatol Pract Concept. 202026;10(4):e2020121. DOI: 10.5826/dpc.1004a121. PMID: 33150042. PMCID: PMC7588151. 2. Liebman TN, Rabinovitz HS, Dusza SW, Marghoob AA. White shiny structures: dermoscopic features revealed under polarized light. J Eur Acad Dermatol Venereol. 2012;26(12):1493-1497. 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