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 Table of Contents  
Year : 2020  |  Volume : 7  |  Issue : 2  |  Page : 64-69

Study of seborrheic keratosis by dermoscopy using polarized and nonpolarized modes

Department of Dermatology, Venereology and Leprosy, Government Medical College and Sir T Hospital, Bhavnagar, Gujarat, India

Date of Submission17-Apr-2020
Date of Decision15-Jun-2020
Date of Acceptance24-Oct-2020
Date of Web Publication22-Dec-2020

Correspondence Address:
Dr. Hita Mehta
201, Golden Arc Apartment, Atabhai Chowk, Bhavnagar, Gujarat
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijdpdd.ijdpdd_48_20

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Background: Seborrheic keratosis (SK) is the most common benign skin tumor. Dermatoscope is a simple noninvasive diagnostic tool. Although SK has been well recognized clinically, dermoscopically, and histopathologically, data regarding dermoscopic differentiation of different types of SK using the polarized (P) and nonpolarized (NP) modes of dermoscopy are inadequate. Objectives: The objective was to study the dermoscopic pattern of different types of SK under P and NP dermoscopic modes. Methodology: A descriptive study of 102 patients was carried out after ethical approval. All patients attending the dermatology outpatient department with lesions who were willing to participate in the study were included in the study after taking written informed consent. After a detailed history and examination, clinical and dermoscopic photographs were taken under the P and NP modes of a dermoscope attached with a smartphone camera. Biopsy of the same lesions was sent for a histopathology examination. Results: A total of 102 patients were studied. Females (58) outnumbered males (44). The most common clinical variant was common SK. The most common histopathological type of SK was hyperkeratotic followed by acanthotic type. Sharp demarcated border (75%) was the most common finding on dermoscopy in our study followed by fissure and ridges (63%), scales (54%), comedo-like opening (34%), cobblestone-like pattern (33%), moth-eaten border (17.7%), and cerebriform pattern (13.7%). Conclusion: NP mode helps in better visualization as well as depth perception, whereas P mode shows better color perception and sharpness of superficial as well as deep dermoscopic structures.

Keywords: Dermoscopy, nonpolarized and polarized modes, seborrheic keratoses

How to cite this article:
Sonagara B, Mehta H, Astik B, Agrawal N. Study of seborrheic keratosis by dermoscopy using polarized and nonpolarized modes. Indian J Dermatopathol Diagn Dermatol 2020;7:64-9

How to cite this URL:
Sonagara B, Mehta H, Astik B, Agrawal N. Study of seborrheic keratosis by dermoscopy using polarized and nonpolarized modes. Indian J Dermatopathol Diagn Dermatol [serial online] 2020 [cited 2021 Sep 27];7:64-9. Available from: https://www.ijdpdd.com/text.asp?2020/7/2/64/304338

  Introduction Top

Seborrheic keratoses (SK) are the most common benign epidermal tumors composed of epidermal keratinocytes.[1] SK usually occurs in middle-aged individuals, but it can also be seen in adolescence. SK has equal preponderance in both genders.[1],[2] The most commonly affected sites are face and upper trunk although any other site can be affected.[1] The lesions are usually asymptomatic; they present as round-to-oval, raised, sharply demarcated papules or plaques and are light-brown to black, with few having a waxy verrucous or “stuck-on” appearance. Although SK has been well recognized clinically, dermoscopically, and histopathologically, data regarding dermoscopic differentiation of different types of SK using the polarized (P) and nonpolarized (NP) modes of dermoscopy are inadequate. SK is a common condition with many dermoscopic features which are also common to other pigmented lesions, so we choose SK to study. Hence, this study was carried out to study the different dermoscopic patterns of clinical variants of SK under P and NP modes of dermoscopy.

  Methodology Top

A descriptive study comprising a total of 102 patients was carried out at the outpatient department (OPD) of dermatology after obtaining ethical approval from the institutional ethical committee. Any patient attending the dermatology OPD, with age above 15 years, irrespective of sex, clinically diagnosed as SK, and willing to participate in the study, was included in the study after taking written informed consent. Patients who refuse for clinical photographs and biopsy, those with a lesion with infection, and those with grossly malignant lesions were excluded from the study. After enrolling the patients, thorough history taking and detailed examination were done. Parameters such as age, sex, age of onset, family history, duration of lesions, site of lesions, morphology, sun exposure history, and family history were recorded by using a predesigned case record form. Dermoscopy was performed in all cases by randomly choosing a single lesion of a patient clinically diagnosed as SK by a dermatoscope (Dermlite DL4 - 3Gen Inc, 31521 Rancho Viejo Road, San Juan Capistrano, CA, USA) attached to a smartphone with the smartphone adaptor and stored. The same lesions were biopsied for histopathological diagnosis. The images were analyzed; dermoscopic features and patterns were stored and assessed by two observers.

Before conducting the study, a literature search was done using PubMed and many other databases with the following keywords: “Dermoscopy/polarized and non-polarized mode” for seborrheic keratosis. The dermoscopic features included for the study were sharp demarcated border (SDB), comedo-like openings (CLO), cerebriform pattern (CFP), milia-like (ML) cysts, fissures and ridges (FR), fingerprint (FP)-like structures, moth-eaten border, hairpin (HP) blood vessels, network-like (NL) structures, cobblestone-like pattern (CSP), fat finger (FF), opaque brown pigmentation (OBP), coral-like structure (CLS), and scales (S).

All data were plotted on excel sheets. Categorical and nominal data were expressed in percentages. Categorical data were analyzed using a Chi-square test. Fisher's exact test was applied when variables were too small in number. The significance threshold of the P value was set at <0.05. The comparison between two different modes of dermoscopic findings was determined by Chi-square and Fisher's exact test. All analyses were carried out by usingGraphPad INSTAT software version 3.06, 32 bit for Windows (GraphPad software Inc.11452 EL Camio Real, San Digeo 92130,USA).

  Results and Observations Top

In the present study, a total of 102 patients were studied. Females (58) outnumbered males (44) in our study. SK was most common in above 60 years' age group (61.7%) followed by 50–59 years' age group (18.6%), 40–49 years' age group (11.7%), 30–39 years' age group (6.8%), and only one case (0.9%) in 15–23 years' age group.

The most common clinical variant was common SK (49%) followed by stucco keratosis (27.4%), pedunculated SK (10.7%), flat SK (8.8%), and dermatosis papulosa nigra (3.9%). A history of sun exposure was present in 67 patients. A total of 12 patients had a positive family history of SK among the 102 patients. The most common site of SK in our study was upper extremities (72.5%) followed by face (55.8%), trunk (34.3%), lower extremities (25.4%), and neck (19.6%).

The presence of SDB (75%) was the most common finding on dermoscopy in our study followed by FRs (63%). HP blood vessels were not seen in any of our patients. The difference between dermoscopic features under P and NP modes and their statistical significance are described in [Table 1].
Table 1: Differences between polarized and nonpolarized modes among dermoscopic features of seborrheic keratosis

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Some dermoscopic features are better seen under P mode, whereas other features are better seen under NP mode. We observed that under P mode, dermoscopic features such as scales (55%), OBP (36%), CSP (33%), moth-eaten border (17.7%), FFs (6.9%), CLS (5.9%), FP-like pattern (2.9%), ML cyst (2%), and NL structures (2%) were more apparent [Figure 1] and [Figure 2]. Among them, CSP and OBP were statistically significant compared to NP mode [Table 1]. Whereas under NP mode, fissure and ridges (63%), CLO (34%), and CFP (13.7%) were more apparent [Figure 1], from which fissure and ridges finding was statistically significant [Table 1]. SDB was equally evident in both modes. We observed few differences in dermoscopic structures under P and NP modes of dermoscopy, which are shown in [Table 2].
Figure 1: Polarized and nonpolarized modes of dermoscopy for common (a and b), stucco (c and d), and pedunculated (e and f) variants of SK. White arrow – comedo-like opening, yellow arrowhead – sharp demarcated border, star – moth-eaten border, white circle – fat fingers, red arrow – fissures and ridges

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Figure 2: Polarized and nonpolarized modes of dermoscopy for stucco (a-d) and flat (e and f) variants of SK. Black circle – cobblestone-like pattern, black triangle – fingerprint-like structure, black arrow – network-like structure

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Table 2: Differences observed in structures seen under polarized and nonpolarized dermoscopy

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CLO on dermoscopy was described as round-to-oval, black- to dark brown-colored cleft containing keratin plug. In our study, CLOs were visible under both modes, but the depth and border of CLO were better seen under NP mode, whereas the color of CLOs was darker under P mode [Figure 1]a and [Figure 1]b. Features such as SD border, moth-eaten border, and OBP were observed under both P and NP modes but better appreciated under P mode [Figure 1]a and [Figure 1]b.

Fissure and ridges appeared as gyri and sulci with more brownish appearance under NP mode, and here the depth of FR was better seen [Figure 1]e and [Figure 1]f. We observed that in the flat variant of SK, FR also appears as a FF which looks as multiple, flat, raised lines with finger-like configuration, better under P mode.

CSP, FP-like pattern, and NL structure were well appreciated under P mode compared to that of NP mode [Figure 2]. CSP was observed when multiple squares or angulated shape globules were in arrangement close to each other but separated by thin lines. This pattern was observed more commonly in the flat, common, and stucco variants of SK. NL structures represent hyperpigmented lines within structures with an interposed depigmented circular hole in between. Starburst pattern was an interesting finding seen in one case and it was better appreciated under P mode [Figure 3].
Figure 3: Polarized and nonpolarized modes of dermoscopy for stucco (a and b) variant of SK. Arrow – starburst pattern at the periphery of lesion

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The most common histopathological type of SK was hyperkeratotic (38 cases, 37.2%), followed by acanthotic type (30 cases, 29.4%), reticulated type (25 cases, 24.5%), stucco type (3 cases, 2.9%), melanoacanthoma (1 case, 0.9%), clonal type (1 case, 0.9%), and inverted follicular (1 case, 0.9%) [Figure 4]. Hyperkeratosis was the most common finding on histopathology seen in 98% of the cases followed by basal pigmentation in 78.4%, acanthosis in 73.5%, papillomatosis in 61.7%, orthokeratosis 53.9%, lymphocytic infiltration 50%, true horn cyst 27.4%, and pseudocyst formation in 13.7%.
Figure 4: Histopathological variants of seborrheic keratosis (a-hyperkeratotic, b-acanthotic, c- reticulated, d- inverted follicular, e-malanoacanthotic, f- clonal) (H and E, ×10)

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  Discussion Top

SK is a common benign pigmented tumor. Diagnosis of SK is mostly clinical, but sometimes, it is difficult to differentiate between SK and many pigmented skin lesions such as pigmented basal cell carcinoma, blue nevus, atypical nevus, and cutaneous melanoma.[3],[4] An abrupt and striking increase in the number and/or size of SKs occurring before, during, or after an internal malignancy called “sign of Leser–Trélat” is a rare cutaneous marker of internal malignancy, in particular gastric or colonic adenocarcinoma.[5]

Dermoscopy has two modes, that is, P and NP. Although it is well known that the P mode helps in a better appreciation of deeper structures whereas NP mode shows a magnified image of the superficial structure of the skin, it is also important to know that how a particular feature differs in two different modes. We studied dermoscopic findings for various clinical types, and the presence or absence of these features could help in diagnosing the various types of SK. Although some dermoscopic features are visible under both modes, we observed certain differences among them, which might be helpful to choose the appropriate mode for that particular feature [Table 2].

FRs were previously called “gyri and sulci.”[6] Minagawa et al. described FR as thick, curved, occasionally branched lines whose colors vary from hypopigmented to brown-black. They also described that when FR appear as straight, flat, and slightly elevated, it was termed “fat finger” and, when FRs spread throughout the lesion, it gives the cerebriform or brain-like appearance.[6] FRs, FF, and cerebriform appearance correspond to the papillomatous surface of the epidermis on histopathology [Figure 5].[6] In our study, FR, FF, and CFP showed papillomatosis on histopathology in 45%, 57%, and 57.17% of cases, respectively.
Figure 5: Dermoscopy – histopathology correlations: Fissure and ridges correlate with papillomatosis, comedo-like opening correlates with epidermal horn cyst, and brownish background correlates with basal pigmentation (histopath figure – H and E, ×10)

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Alapatt et al. observed that CLO on dermoscopy correlates with papillomatosis and pigmentation, whereas Minagawa correlated it with pseudohorn cyst histopathologically.[6],[7] In our study, histopathology of the lesion with CLO showed papillomatosis in 54%, pigmentation in 82%, and pseudohorn cyst in 22% of cases.

Various studies have been performed regarding dermoscopy of SK, but we could not find any study which compared various dermoscopic features among P and NP modes. We compared the dermoscopic findings of SK in other similar studies, which are shown in [Table 3].[2],[6],[8] HP blood vessels were not seen in any of our patients, which may be due to the dark-colored Asian skin and this observation was also seen in other studies.[9],[10]
Table 3: Comparison of frequency of dermoscopic features of other similar studies

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One of our patients was clinically diagnosed with a pedunculated SK, but histopathologically reported as a wart. Dermoscopy of that lesion showed FRs, CLO, and few brown dots; histopathology showed parakeratosis, keratin invagination, and papillomatosis along with vacuolated basal keratinocytes [Figure 6]. We observed that even though the lesion had FRs and CLO which are generally seen in SK, the presence of brown dots helped us to differentiate wart from SK. The importance of brown dots in the diagnosis of wart had also been described in another study.[9] Dermoscopic features such as blue-white veil, blue globular pattern, and HP vessels which were mentioned in other published studies were not seen in our study.
Figure 6: Clinically similar looking two pedunculated lesions under polarized mode dermoscopy. (a and b) Clinical photograph, (c and d) Dermoscopy – polarized mode, (e and f) Histopathology images. Note the presence of brown dots in d and absence in c. White arrow – comedo-like opening, yellow arrowhead – fissure and ridges, inset enlarged image – brown dot (histopath figure – H and E, ×10)

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  Conclusion Top

We observed that some dermoscopic features such as fissure and ridges, CSP, and OBP show statistically significant difference in NP and P modes of dermoscopy, so both modes should be used for better visualization of detailed dermoscopy features of SK. A larger sample is required to draw a better inference.

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Conflicts of interest

There are no conflicts of interest.

  References Top

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Rajesh G, Thappa DM, Jaisankar TJ, Chandrashekar L. Spectrum of seborrheic keratoses in South Indians: A clinical and dermoscopic study. Indian J Dermatol Venereol Leprol 2011;77:483-8.  Back to cited text no. 2
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Braun RP, Rabinovitz HS, Krischer J, Kreusch J, Oliviero M, Naldi L, et al. Dermoscopy of pigmented seborrheic keratosis: A morphological study. Arch Dermatol 2002;138:1556-60.  Back to cited text no. 4
Yeh JS, Munn SE, Plunkett TA, Harper PG, Hopster DJ, du Vivier AW. Coexistence of acanthosis nigricans and the sign of Leser-Trélat in a patient with gastric adenocarcinoma: A case report and literature review. J Am Acad Dermatol 2000;42:357-62.  Back to cited text no. 5
Minagawa A. Dermoscopy-pathology relationship in seborrheic keratosis. J Dermatol 2017;44:518-24.  Back to cited text no. 6
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  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]

  [Table 1], [Table 2], [Table 3]


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