Pigment International

ORIGINAL ARTICLE
Year
: 2022  |  Volume : 9  |  Issue : 2  |  Page : 93--106

Role of dermoscopy in the assessment of difficult to diagnose cases of pigmentary dermatoses: study from a tertiary care hospital


Yasmeen J Bhat, Faizan Y Shah, Insha Latif, Najm-u Saqib, Aaqib A Shah, Yaqzata Bashir, Rita Devi, Uzair K Dar, Masarat Naushad, Iffat Hassan, Kewal Krishan 
 Department of Dermatology, STDs & Leprosy, Government Medical College, Srinagar, Jammu & Kashmir, India

Correspondence Address:
Dr. Yasmeen J Bhat
Department of Dermatology, Venereology & Leprosy, Government Medical College, University of Kashmir, Srinagar 190010, Jammu & Kashmir
India

Abstract

Background: Pigmentary disorders are a common skin affliction causing great distress and anguish among those affected. Dermoscopy is a noninvasive diagnostic modality which has great potential in the diagnosis of these disorders. Objectives: To assess the dermoscopic features relevant to the diagnosis of pigmentary dermatoses in patients presenting to our tertiary care hospital. Methods: This was a cross-sectional study conducted in patients presenting to pigmentary dermatoses clinic of our hospital over a period of 1 year. A comprehensive evaluation with special emphasis on dermoscopy was performed in all patients. The dermoscope used was DL3N Dermlite (10X). Additional investigations were carried out as deemed necessary to clinch a final diagnosis. Results: The study included a total of 200 cases with 90 males and 110 females, with age ranging from 6 months to 69 years and a mean age of 24.43 ± 17.07 years. The pigmentary dermatoses encountered were divided into three groups − disorders of hypopigmentation, facial melanoses, and other pigmentary disorders. Dermoscopic findings most relevant to diagnosis were compiled and tabulated. Conclusion: Dermoscopy played a significant role to rule out ominous diagnosis with accuracy comparable to histopathology, when carried out by an expert. The need for an invasive procedure such as skin biopsy was evaded in a number of cases.



How to cite this article:
Bhat YJ, Shah FY, Latif I, Saqib Nu, Shah AA, Bashir Y, Devi R, Dar UK, Naushad M, Hassan I, Krishan K. Role of dermoscopy in the assessment of difficult to diagnose cases of pigmentary dermatoses: study from a tertiary care hospital.Pigment Int 2022;9:93-106


How to cite this URL:
Bhat YJ, Shah FY, Latif I, Saqib Nu, Shah AA, Bashir Y, Devi R, Dar UK, Naushad M, Hassan I, Krishan K. Role of dermoscopy in the assessment of difficult to diagnose cases of pigmentary dermatoses: study from a tertiary care hospital. Pigment Int [serial online] 2022 [cited 2022 Sep 30 ];9:93-106
Available from: https://www.pigmentinternational.com/text.asp?2022/9/2/93/353671


Full Text



Key Messages

We found dermoscopy to be an invaluable noninvasive diagnostic technique in the management of pigmentary disorders. Analyzed by an expert, dermoscopic findings in some of these disorders can be as reliable as histopathology. Given the fact that these disorders are mostly benign and do not warrant an invasive procedure such as biopsy, dermoscopy may completely replace histopathology as the diagnostic method of choice in the near future.

 INTRODUCTION



Normal skin color is determined by melanin in combination with oxyhemoglobin, reduced hemoglobin, and carotenoids.[1],[2] Variation in skin color among individuals and races is related to the number, distribution, and degree of melanization of melanosomes.[3] Pigmentary disorders occur as a result of abnormal distribution, dysfunction, or destruction of melanocytes. Increase or decrease in melanin content of epidermis results in hypermelanosis or hypomelanosis, respectively. Rarely, hyperpigmentation may occur due to abnormalities in keratinocyte proliferation.[4] Although histopathology still remains the gold standard in the diagnosis of pigmentary disorders, most of these are generally benign and do not warrant an invasive procedure such as skin biopsy.[5],[6] Dermoscopy has recently emerged as a probable substitute to histopathology in the hands of an expert, which can assertively clinch a diagnosis and where this is not possible, minimize, and rationalize cases which need confirmation using skin biopsy.[7],[8],[9],[10],[11]

Dermoscopy, also known as skin surface microscope or epiluminescence microscope, is a noninvasive diagnostic modality used to visualize skin structures and patterns of skin lesions up to the depth of reticular dermis.[12] It has been used most extensively and constructively in the study of melanocytic nevi and melanomas.[13],[14] This technique has immense potential in assisting the diagnosis of pigmentary dermatoses which has not been tapped adequately.

Dermoscopy of normal skin demonstrates brown lines arranged in a reticular pattern resembling a honeycomb with white or light brown circles between them.[15] This is referred to as pigment network which is homogenous in color with regular and uniform pattern. The brown lines correspond to melanin in the epidermis arranged along rete ridges, whereas the tips appear white to light brown. This occurs due to higher concentration of melanin in the slope of rete ridges. True pigment network, which is a hallmark of body skin, is rarely encountered on face. Facial skin demonstrates pseudonetwork constituted by diffuse brown pigmentation interrupted by light brown circles or holes. This pattern is attributed to distribution of melanin along flat rete ridges of epidermis, whereas holes correspond to pilosebaceous and sweat gland openings.[16]

This study was conducted to evaluate the cases of pigmentary dermatoses and present relevant dermoscopic features which assist diagnosis and assess the reliability of dermoscopy in clinching a diagnosis and evading the need for invasive procedures such as skin biopsy.

 MATERIALS AND METHODS



The study was a cross-sectional analysis of the patients presenting to the pigmentary dermatoses clinic in our department over a period of 1 year, conducted after institutional ethical clearance was taken. Scheduled once a week, the pigmentary dermatoses clinic of our department cater to the cases which pose a diagnostic dilemma in the out-patient department and need a comprehensive evaluation to arrive at a final diagnosis. This involves a detailed history taking, cutaneous and systemic examination, bedside investigations such as Wood lamp and dermoscopy, and invasive procedures such as skin biopsy for histopathological examination (HPE) and immunohistochemical examination in selected cases. The dermoscope used was DermLite DL3N and Dermlite 4 (10x magnification), manufactured by (3Gen, California, USA) and the images were captured with iphone-6S. Normal skin was visualized with the dermoscope, before examining the lesion, for comparison. This was followed by visualization in the polarized mode with pigment boost. Linkage fluid such as absolute alcohol or ultrasound gel was also used in some cases.

All the patients referred to the clinic over a period of 1 year were enrolled in the study after taking an informed consent. Those who did not consent were excluded. The data of patients were compiled in the form of a master chart and were presented with particular emphasis on relevant dermoscopic features that assisted diagnosis. The parameters studied included pigmentary network, color of the pigment (black, dark brown, brown, gray, and blue), pigment structures (blotches, dots, globules, clods), perifollicular and perieccrine sparing/involvement, vessels in the form of dots, and other patterns.

 RESULTS



The study included a total of 200 cases with 90 males and 110 females. The age of the patients ranged from 6 months to 69 years with a mean age of 24.43 ± 17.07 years. Majority of the patients (58.5%, n = 117/200) belonged to rural areas, whereas the remaining (41.5%, n = 83/200) were from urban areas. The diagnoses encountered in these cases are enumerated in [Table 1].{Table 1}

For the sake of convenience and easy comprehension, the pigmentary dermatoses encountered during the course of this study were divided into three groups − disorders of hypopigmentation, facial melanoses, and other pigmentary disorders. The dermoscopic findings observed in different patients were compiled and the most significant findings along with other relevant investigations are detailed in [Table 2] and [Table 3]. The relevant dermoscopic images are also presented in [Figure 1][Figure 2][Figure 3][Figure 4] for disorders of hypopigmentation, [Figure 5][Figure 6][Figure 7][Figure 8][Figure 9][Figure 10] for facial melanoses, and [Figure 11][Figure 12][Figure 13][Figure 14][Figure 15][Figure 16][Figure 17][Figure 18][Figure 19][Figure 20][Figure 21][Figure 22][Figure 23][Figure 24][Figure 25][Figure 26][Figure 27] for other pigmented lesions. Skin biopsy for HPE was performed in cases difficult to diagnose clinically and dermoscopically.{Table 2}{Table 3}{Figure 1}{Figure 2}{Figure 3}{Figure 4}{Figure 5}{Figure 6}{Figure 7}{Figure 8}{Figure 9}{Figure 10}{Figure 11}{Figure 12}{Figure 13}{Figure 14}{Figure 15}{Figure 16}{Figure 17}{Figure 18}{Figure 19}{Figure 20}{Figure 21}{Figure 22}{Figure 23}{Figure 24}{Figure 25}{Figure 26}{Figure 27}

 DISCUSSION



Pigmentary disorders form a common complaint among patients which cause significant social and psychological impact on sufferer including a low self-esteem, depression, and even suicidal tendencies in extreme cases. Although most pigmentary dermatoses are not lethal, some like melanoma and basal-cell carcinoma (BCC) can lead to significant morbidity and at times mortality. This highlights the importance of early diagnosis and treatment of pigmentary disorders and the need to distinguish them from more sinister disorders. Dermoscopy has been used extensively in the diagnosis and follow-up of pigmented lesions and is believed to increase the diagnostic accuracy by 5% to 30% depending on the type of lesion and experience of the user.[17] The diagnostic accuracy for melanocytic and nonmelanocytic pigmented lesion, differentiating benign and malignant pigmented lesions, and melanoma detection is greatly aided by using a dermoscope.[18],[19],[20]

The relevance of dermoscopy in diagnosis of pigmentary dermatoses in our study is discussed further. Melanocytes are present in higher numbers in slope when compared with tip of rete ridges, resulting in reticular pattern in normal skin on dermoscopy, with pale areas corresponding to tips of rete ridges. The different colors observed on dermoscopy can be attributed to chromophores. These include − dirt/dust on hair or skin (black/brown), keratin (brown), sebum (yellow), blood (black or red), and collagen (white). Melanin is another chromophore which can ascribe various colors depending on depth of pigment − stratum corneum (black), stratum malpighii (light to dark brown), papillary dermis (gray), and reticular dermis (blue).[21] This variation in color can be attributed to Tyndall effect, wherein short wavelength blue light is dispersed more when compared with other colors.[22] The different chromophores accumulate in various planes and form varied morphologies, resulting in typical appearances which are identified using a dermoscope.

Dermoscopy was found useful in differentiating vitiligo from other hypopigmentary disorders and in assessing disease stability. Features such as perifollicular hyperpigmentation, marginal hyperpigmentation, and marginal reticular pigmentation indicate stability. Star burst, salt and pepper, polka dot pattern, and comet tail appearance indicate active disease. Reverse pigment network is an important finding to detect early unstable vitiligo. In progressive vitiligo, loss of melanocytes results in lightening of pigmented areas when compared with pale areas with resulting reversal of pigment network.[23] Irregular and serrated border with pseudopods on dermoscopy along with normal colored hair and absence of hyperpigmented border helps to differentiate nevus depigmentosus from vitiligo. Clinical criteria devised by Coupe for diagnosis of nevus depigmentosus include: leukoderma present at birth or early onset; no change in distribution throughout life; no alteration in texture or sensation; and absence of a hyperpigmented border.[24] Idiopathic guttate hypomelanosis demonstrates structureless areas on dermoscopy which appears to glow due to loss of mealnocytes. However, the glow is not as uniform as vitiligo and contains multiple shades of white. Dermoscopy helps in better pickup of findings and in differentiating common mimics.

In Lichen planus pigmentosus (LPP), dots and globules were the most common findings, whereas more specific features comprised hem-like pattern, accentuation of reticular pattern, and perifollicular deposition of pigment. Dots and globules are believed to be related to pigment incontinence.[25] Accentuation of pigment pseudonetwork and gray dots/granules were the most suggestive dermoscopic features of Riehl melanosis on the face. Gray to brown dots/granules observed on dermoscopy correspond to the presence of melanophages in dermis, secondary to vacuolar degeneration of basal cells, and pigment incontinence.[26] On dermoscopy of melasma, melanin appears dark brown with a well-defined network when located in stratum corneum. A light brown color with an irregular network is observed when melanin is located in lower layers of the epidermis, whereas bluish gray color indicates dermal pigment.[27] The variation in color observed on dermoscopy is due to Tyndall effect, in which short-wavelength blue light is dispersed and reflected more than long-wavelength light.[28] Bluish gray amorphous areas obliterating follicular openings help to distinguish exogenous ochronosis from melasma. Bluish gray color, not ochre as in histopathology, is observed on dermoscopy of ochronosis, attributed to the depth of pigment and to Tyndall effect.[29] In erythromelanosis follicularis faciei et colli, dermoscopy shows multiple round whitish areas with follicular plugs surrounded by bluish gray spots in a reddish brown background.[30]

Dermoscopy can help differentiate congenital melanocytic nevi (CMN) and Becker nevus (BN). BN does not show polymorphism of CMN as hyperpigmented areas, cobblestone structures, and globules are generally lacking which can be attributed to the clinical monomorphism of BN.[31] Dermoscopic feature such as milia-like cysts, moth-eaten border, finger print structures, cerebriform pattern, and comedo-like openings are considered specific to the diagnosis of seborrheic keratosis. Histopathological changes form the basis for these features. Papillomatosis accounts for comedo-like openings, whereas milia-like cysts correspond to keratin-filled cysts, known as horn cysts.[32] In acanthosis nigricans (AN), aberrant skin structure of linear crista cutis and sulcus cutis, and hyperpigmented dots in crista cutis are diagnostic on dermoscopy.[33] Nonpolarized mode offers better visualization of findings in AN as pathology lies in the superficial layers of skin.[34] Dermoscopy in post-inflammatory hyperpigmentation (PIH) helps to guide whether the pigment is predominantly epidermal or dermal. Features are nonspecific and no consistent pattern is observed.[35]

Red dots and globules, dotted and blotchy red vessels in perifollicular areas with surrounding brownish, pigmented dots and clots are dermoscopic pointers toward a diagnosis of Schamberg disease. The red dots, globules, and patches correspond histologically to extravasation of red blood cells and an increased number of blood vessels which may be dilated. Brown globules and dots are a result of spherical or elliptical organization of melanocytes or melanophages at the dermoepidermal junction.[36] In macular amyloidosis, the most common dermoscopic finding is a central hub, which can be either white or brown, surrounded by various configurations of pigmentation.[37] Alteration in background pigmentation is a common feature of pityriasis versicolor (PV) on dermoscopy. Fine scaling observed on dermoscopy can help differentiate atypical cases of PV from other hyperpigmented disorders.[38] Increased pigmentation is believed to be secondary to thickening of stratum corneum and lymphocytic infiltrate in the dermis which stimulates melanogenesis.[39]

Dermoscopy helps to distinguish Darier disease from its main clinical differentials. Central yellowish brown area surrounded by white halo overlying pinkish structureless area with adjacent dotted and linear vessels is a significant feature which assists diagnosis. The central yellowish brown area and its whitish halo correspond to the compact hyperkeratosis and acanthosis, respectively, whereas the pinkish background and vessels can be attributed to dermal inflammation.[40],[41]

Dermoscopy can be used to differentiate verrucous epidermal nevus (VEN) from potential malignant growths. Although similar dermoscopic findings may be shared by seborrheic keratosis and dermal nevus, all three are benign and thus fear regarding a malignancy is allayed.[42] The large brown circles observed correlate histologically to typical organization of pigmented keratinocytes around the dermal papillae.[43] In porokeratoses, dermoscopy reveals central white area of scarring, reddish brown dots and globules, and vessels of different patterns.[44] Pigmented Bowen disease has a characteristic dermatoscopic pattern of linear arrangement of brown and/or gray dots and/or coiled vessels.[45] The erythema ab igne is typically characterized by diffuse brownish pigmentation with or without telangiectatic vessels/whitish scaling.[46]

Ulceration, maple leaf-like areas, large grayish blue ovoid nests, multiple grayish blue globules, spoke wheel areas, and arborizing vessels are considered dermoscopic criteria significant for diagnosis of BCC. Bluish gray ovoid nests occur due to large tumor nests in dermis, whereas leaf-like areas correlate with small basaloid cell nests at the dermoepidermal junction.[47] Moth-eaten edge of ephelides on dermoscopy help to differentiate it from blue nevus, Spitz nevus, Reed nevus, etc. Uniform pigmentation occurs as a result of increased melanin content inside basal keratinocytes.

In dermatofibroma, the most common dermoscopic feature is a central white scar-like patch with delicate pigment network at the periphery.[48] On dermoscopy, maturational pigmentation demonstrates brown rings concentrated around follicular openings and lacks features of crista and sulci cutis, which helps to differentiate from the closest differential AN. The findings correspond to histological features of significant basal layer melanization with slight papillomatosis.[49]

Dermoscopy has been greatly beneficial in differentiating melanoma from various clinical mimics thus averting need for skin biopsy. It has improved the benign to malignant biopsy ratio (B:M ratio) from 45:1 to between 4 to 7:1.[50] The cobblestone pattern on dermoscopy of melanocytic nevi corresponds to melanized keratinocytes situated in the basal and spinous layers of the skin. Solar lentigo can be distinguished from LMM based on four criteria for LMM including asymmetrical pigmented follicular openings, rhomboidal structures, annular-granular structures, and gray pseudonetwork as described by the consensus net meeting on dermoscopy.[51] Differentiation of subungual hematoma from melanoma can be improved using a dermoscope. Subungual hemorrhages usually appear brown or black to naked eye but red and purple color components have been observed with dermoscopy. Additional red or purple streaks may be encountered in older lesions owing to fresh bleeding due to repetitive trauma.[52] On dermoscopy, longitudinal melanonychia is brownish black, restricted to nail plate, and has a longitudinal aspect. A gray background of the band with thin grayish regular and parallel lines along with pigmentation of periungual skin suggests a melanocytic activation. Distinction from melanoma can be made as melanoma shows rapid progression of brown background with longitudinal brown to black lines with varying color pigmentation, spacing or thickness, ending abruptly, and positive micro-Hutchinson sign.[53] Venous lakes can be confused for LMM especially on the lips. Structureless pattern and lacune on dermoscopy are believed to be related to dilated vascular spaces.[54] A combination of blue, gray, or white color with structureless zones is a strong pointer toward malignancy in pigmented mucosal lesions.[19]

This study involved the evaluation of patients with pigmentary disorders who posed a diagnostic dilemma and were evaluated in the pigmentary dermatoses clinic. A detailed evaluation and investigations, particularly dermoscopy, paved the way for precise diagnosis and treatment in these patients. Dermoscopy played a substantial role in the diagnosis, often helping to rule out sinister diagnosis with accuracy that was found to be comparable to histopathology, when carried out by an expert. The need for an invasive procedure such as skin biopsy was evaded in a number of cases.

 CONCLUSION



Dermoscopy is an instrumental technique, helpful not only in diagnosis but also in monitoring disease progression and response to treatment. It may form a noninvasive alternative for HPE in pigmentary dermatoses in the near future. However, to make this dream a reality, many more studies of this sort will have to be undertaken and much more expertise will have to be gained in the field of dermoscopic evaluation. We hope that our study is a source of contribution in this direction.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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