Nail apparatus melanoma: dermoscopic and histopathologic correlations on a series of 23 patients from a single centre

DOI: 10.1111/jdv.14568 JEADV ORIGINAL ARTICLE Nail apparatus melanoma: dermoscopic and histopathologic correlations on a series of 23 patients from a single centre M. Starace, E. Dika, P.A. Fanti, A. Patrizi, C. Misciali, A. Alessandrini, F. Bruni, B.M. Piraccini* Dermatology, Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Bologna, Italy *Correspondence: B.M. Piraccini. E-mail: biancamaria.piraccini@unibo.it Abstract Background Nail apparatus melanoma (NAM) is an uncommon tumour, and there are few studies focused on its dermoscopic features. Objective The aims of our study were to evaluate the diagnostic accuracy of dermoscopy in NAM. A diagnostic algorithm for adult patients with suspected NAM is proposed. Methods We collected NAM dermoscopic images of patients with a proven histopathology from 2008 until 2015. Clinical and dermoscopic images were blindly examined by two dermatologists, and correlations between histopathological aspects and dermoscopic features were investigated. Results We retrospectively collected NAM dermoscopic images associated with a proven histopathology of 23 Caucasian patients. Only cases with available both preoperative dermoscopic images and bioptic specimens were included. Seventeen women and six men were included. The mean age at diagnosis was 63 years (range 18 92). Conclusion We created an algorithm to indicate the correct way to follow an adult patient with suspected NAM. This algorithm may ameliorate management in case of suspected NAM and possibly facilitate an early diagnosis. Received: 25 January 2017; Accepted: 31 July 2017 Conflicts of interest The authors declare no conflict of interest. Funding sources The authors declare no funding sources supporting the work. Introduction Nail apparatus melanoma (NAM) is an uncommon tumour, especially in Caucasians, with reported incidence between 0.7% and 3.5% in all melanomas: it is considered to represent about 1.5 2% of all melanomas in fair-skinned population 1,2 and to reach higher frequency, over 20% of all melanomas, in darkskinned population. 3,4 NAM usually affects middle-aged or elderly people. It can arise in both fingernails and toenails with highest frequency on great toenail, thumb and the index. Approximately 50% of patients with nail melanoma recollect preceding traumas. 5,6 The diagnostic accuracy of NAM has improved over the years, first of all for the utilization of the ABCDs rule for nail pigmentation 7 and secondarily for the use of nail dermoscopy. 8 Nevertheless, the misdiagnosis rate was found to be higher than 20%. 9 NAM is included in the group of acral lentiginous melanoma, The authors contributed equally to the manuscript. and it can present as melanotic or amelanotic. In most cases, NAM is described as a longitudinal band of brown to black pigmentation within the nail plate (longitudinal melanonychia, LM). The gold standard for the diagnosis of nail pigmentation is histopathology 10 15 that requires an accurate bioptic technique and a trained pathologist in nail diseases. However, dermoscopic features may offer interesting information for the selection of cases in which pathologic examination is indicated. The aim of our study was to describe the dermoscopic characteristics in a series of NAM correlating the latter with the respective histopathologic examinations. Materials and methods We retrospectively examined all cases of NAM referred to the Skin Cancer and Nail Diseases Outpatient Consultations of the Dermatology Unit of the University of Bologna from 2008 until 2015. Only cases with available both preoperative dermoscopic images and bioptic specimens were included. Clinical and

Dermoscopy of nail apparatus melanoma 165 dermoscopic images were blindly examined by two dermatologists (MS, BMP). In our Unit dermoscopy of the nail plate, the distal margin, the periungual tissues and of the hyponychium, is usually performed at the initial visit. We adopt an ultrasound gel for immersion during dermoscopic assessment and utilize a FotoFinderdermatoscope â (Teachscreen Software, Bad Birnbach, Germany). The clinical and dermoscopic features assessed for each NAM were the following: (i) size and shape of the band (longitudinal or triangular with proximal base); (ii) colour of the background: brown, grey or black; (iii) regular or irregular borders; (iv) aspect of the lines: homogeneous or not homogeneous in colour, spacing and thickness; (v) regular or disrupted parallelism; (vi) the presence of dystrophy of the nail plate or partial or total absence; (vii) the presence of Hutchison s sign or micro-hutchinson s sign; (viii) red signs (spots or lines) due to vascular alterations. Histopathologic specimens were also blindly reviewed and re-evaluated by two pathologists (CM, PAF). Data such as Breslow thickness, infiltration thickness, number of mitosis, regression and ulceration were gathered and confronted with the dermoscopic features for each NAM, in a final collegial evaluation. Results All the results are reported in Table 1. We collected data on 23 NAM. All the patients were Caucasian: 17 were women and six were men. The mean age at diagnosis was 63 years (range 18 92). The mean duration of NAM at the time of diagnosis was 2.3 years (range from 6 months to over 10 years). Three patients referred the presence of melanonychia for less than 8 months, six patients for <1 year, nine patients for 2 years and the last five patients for more than 2 years. Only one patient referred the presence of melanonychia since 20 years, with clinical changes appearing the year prior to our consultation. Clinical features The digit most affected in the fingernails was the thumb (eight cases) and in the toenails was the big toe, which was the only localization of NAM of the toes. Four cases of NAM in the fingernails were located on the 3rd digit of the hand, one case on the 2nd, two on the 4th digit and two cases on the 5th digit. Regarding the site of the body, 11 involved the left side, seven on the fingernails and four on the toenails and 12 cases the right side, eight on the fingernails and four on the toenails (Fig. 1). In 14 patients NAM presented as a band of LM, which in four cases were associated with Hutchinson sign, and in seven cases with partial destruction or dystrophy of the nail plate. The width of the band of LM varied from 1 to 7 mm, and in two cases involved the whole nail plate. The colour was grey or brown to black, with a very pale brown colour seen in four cases and a deep brown colour in one case. In all LMs, the colour was not homogeneous. Borders of LM were regular in one case and irregular in 11, in two cases, it was impossible to see the borders as LM involved the whole nail plate. In one patient, LM had a triangular shape, with a larger proximal than distal edge. In nine patients NAM presented as an amelanotic eroded nodule of the nail bed with Hutchinson s sign in two cases. Dermoscopic features Dermoscopic pictures showed the presence of a LM in 14 patients, in four of them associated with Hutchinson s sign; in six of the remaining 10 patients LM was associated with nail plate changes. Dermoscopy showed a brown to black background in 12 cases, with a pale brown in five cases and deep brown in two cases, and grey to black colour in two cases; with blurred lines, often interrupted along the length and irregular margins (Fig. 2) in 10 cases, while in one case lines and borders were regular (Fig. 3). In two cases, it was impossible to observe the lines with dermoscopy. One patient had a triangular shape, with a larger proximal than distal edge. Irregularly distributed microhaemorrhagies were observed in one of the cases that presented a partial destruction of the nail plate and a lateral reddish nodule of the bed. The patient referred the onset of the dystrophy 6 months before our consultation and on histopathologic examination the Breslow thickness (0.3 mm) was the thinnest in our series. Hutchinson s sign was present in four patients, with pigmentation on the proximal nail fold and hyponychium in one case (Fig. 4) and pigmentation of all the digit in three cases and associated with an eroded nodule on the lateral side of the finger. Isolated LM was always due to in situ NAM, while LM associated with Hutchinson s sign and/or with nail plate changes was always due to an invasive NAM. While examining nodular lesions, the nail plate was sometime partially removed to better observe the vascular characteristics of the tumour. In nine patients, dermoscopic images showed an eroded nail bed nodule, which was associated with Hutchinson s sign (Figs. 4 and 5) in two cases and in two other cases with micro-hutchinson s sign. All the latter NAM presented a vascular pattern characterized by a red colour with a milky-red veil and vascular polymorphism (Fig. 6). In four cases, part of the nail plate was present and in five cases the nail plate had completely disappeared. The presence of residual nail plate was correlated with the time of the onset: older lesions presented complete destruction of the nail plate, while in recent lesions a part of the nail plate was still detectable. Also the colour could be correlated with the duration of the lesion. In older lesions, the predominant colour was dark wine-coloured red, probably due to the presence of crusts and vascular disarrangement, as a matter of fact vessels appeared irregular assuming a mix of hairpin, linear or dotty aspect. On the other hand, in younger lesions, the colour was lighter red and presented prominently dotted vessels.

166 Starace et al. Table 1 Anagraphic, clinical, dermoscopic and histopathological features of our 23 cases of nail apparatus melanoma N Sex Age at diagnosis Site Duration Clinical features Dermoscopic aspects Breslow thickness Histopathological parameters 1 F 53 I RF 8 months LM With: 1 mm Colour: deep brown non homogeneous 2 F 57 I LF 1 year LM With: 3 mm Colour: black non homogeneous 3 F 82 I RF 2 years LM With: 7 mm Colour: gray to black non homogeneous 4 F 18 II LF 1 year LM With: 6 mm Colour: black brown non homogeneous 5 F 38 III RF 1 year LM With: 5 mm Colour: black non homogeneous 6 F 53 I RF 2 years LM With: 7 mm proximally and 5 distally (triangular shape) Colour: black non homogeneous Nail plate changes: distal lamellar spitting 7 F 64 III LF 18 months LM With: 6 mm Colour: pale brown non homogeneous Background: black-brown Lines: blurred Micro Background: black Lines: blurred with spacing, interrupted along the length Micro Background: gray to black Lines: blurred Micro Background: brown Lines: regular Micro Background: black Lines: blurred, interrupted along the length Micro Background: black-brown Lines: blurred Micro Nail plate changes: distal lamellar spitting Background: pale brown Lines: regular with spacing Borders: regular Micro

Dermoscopy of nail apparatus melanoma 167 Table 1 Continued N Sex Age at diagnosis Site Duration Clinical features Dermoscopic aspects Breslow thickness Histopathological parameters 8 F 43 I RT 2 years LM With: 6 mm Colour: black non homogeneous along the band 9 M 63 III LF 2 years LM With: 5 mm Colour: pale brown non homogeneous with black dots Nail plate changes: distal splitting and mild onycholysis 10 M 43 I RF 1 year LM: 2 bands With: 6 mm and 2 mm Colour: brown non homogeneous Nail plate changes: partial absence in correspondence of the band Hutchinson s sign: hyponychium and proximal nail fold 11 F 79 V RF 8 months LM and an eroded nodule on the lateral digit With: 5 mm Colour: pale brown non homogeneous Borders: regular Hutchinson s sign: over the whole digit until the I phalanx 12 F 45 I RF 2 years LM With: whole nail Colour: pale brown-gray non homogeneous Borders: NA Nail plate changes: lateral onycholysis, distal splitting Hutchinson s sign: present all over the dorsum of the distal phalanx Background: deep brown Lines: blurred, with great interruptions Micro along the band Background: pale brown Lines: blurred with pigmented brown dots Nail plate changes: distal splitting Micro Background: deep brown Lines: irregular in colour and thickness, interrupted along the length Nail plate changes: partial absence in correspondence of the band Hutchinson s sign: diffuse brown pigmentation with a characteristic broad parallel ridge pattern in the periphery and irregularly distributed brown dots and depigmented areas Background: pale brown Lines: irregular, interrupted along the length Hutchinson s sign: light brown pigmentation of the digit, extending in all three phalanxes, distributed in a broad parallel ridge pattern, accentuated in proximity of a nodular intensely vascularized lesion. The latter presented vascular polymorphism and crystalline like structures. Background: pale brown Lines: blurred Hutchinson s sign: diffuse brown pigmentation of the periungual skin extended up to the second phalanx, a whitish-depigmented papular lesion presenting sparse brown dots at the proximal nail fold. 1mm II+ M1 0.6 mm II + R + 1mm II 1.2 mm II + M1 1mm II+ R +

168 Starace et al. Table 1 Continued N Sex Age at diagnosis Site Duration Clinical features Dermoscopic aspects Breslow thickness Histopathological parameters 13 F 86 IV RF 2 years LM With: whole nail plate Colour: black non homogeneous Borders: NA Nail plate changes: thinning and absence of the distal plate Hutchinson s sign: present all over the distal and II phalanx 14 F 65 III RF 6 months LM with red nodule of the lateral nail bed With: 7 mm Colour: red-brown non homogeneous Nail plate changes: partial absence of lateral plate 15 F 76 I LF 3 years Eroded nodule of the nail bed involving half of the nail 16 M 86 I RT 2 years Eroded nodule of the nail bed involving 1/3 of the nail 17 F 71 I LF 8 years Eroded nodule of the nail bed involving the whole the nail 18 F 49 I RT 1 years Total absence of the nail plate with some eroded areas of the nail bed 19 M 75 V LF 1 year Bleeding granulating mass of the nail bed involving the whole nail Hutchinson s sign: hyponychium Background: black-gray with black dots Lines: not detectable Borders: NA Hutchinson s sign: diffuse dark brown pigmentation of the periungual skin, with a broad parallel ridge pattern extended up to the third phalanx, with depigmented areas in proximity of the lateral and distal nail folds and irregularly distributed black and brown dots Background: pale brown Lines: not detectable Nail plate changes: onycholysis with absent nail plate and distal blood red spots Eroded nodular lesion, presenting different colours ranging from pink to milky red and interlaced with crystalline-like structures. There are splinter haemorrhages toward the distal end of the remnant lamina. Eroded nodule covered by a whitish veil and surrounded at the periphery with yellow to brown scales and crusts. Eroded nodule with milky-red veil and vascular polymorphism. A White- pink nodular lesion, presenting mostly dotted and irregular linear vessels. Micro-Hutchinson s sign: Yellow to light brown pigmentation of the proximal nail fold in an asymmetrical broad parallel ridge pattern A central pink red area, surmounted by a white veil and surrounded by yellow and brown crusts and remnants of a destructed nail plate. Polymorphous vascular pattern. Eroded nodule with milky-red veil and irregular vessels. Hutchinson s sign: brown pigmentation of the distal nail fold distributed in an irregularly mixed parallel ridge and furrows pattern with sparse black dots, white veil and depigmented area nearby the nail plate and some grey globules. 2mm II M2 0.3 mm II ++ 1mm II+ M15 1mm II++ M1 R + 0.8 mm II ++ M4 R + 3.5 mm II ++ 7mm II+ M4

Dermoscopy of nail apparatus melanoma 169 Table 1 Continued N Sex Age at diagnosis Site Duration Clinical features Dermoscopic aspects Breslow thickness Histopathological parameters 20 F 92 I LT >10 years Total absence of the nail plate with black and pink coloured nodules also present on the proximal nail fold and dorsum of the digit 21 M 61 I LF 3 years Absence of the nail plate except for the lateral parts with eroded and keratotic nodules of the nail bed 22 M 82 I LT 3 years Total absence of the nail plate with eroded nail bed and white-black discoloration Hutchinson s sign: present 23 F 68 IV RF 2 years Total absence of the nail plate with some eroded areas of the nail bed Skin coloured to violaceus papular and nodular lesions covering entirely the nail bed, and extending to the skin of last phalanx. A white veil covers the violaceus vascular nodules whereas the polymorphous pattern is perceptible only in the eroded one, localized in the centre of the nail bed. Yellow scales and crusts are diffusely distributed Eroded nodule with milky-red veil, polymorphous vessels, yellow and brown crusts and destroyed portions of the nail plate. Micro-Hutchinson s sign: Diffuse pigmented brown dots at the hyponychium Eroded nodule with milky-red veil and irregular vessels Hutchinson s sign: brown to black pigmentation of the lateral nail folds and hyponychium, broad parallel ridge pattern, sometimes disrupted by gray or white depigmented areas. White and Black dots irregularly distributed 6mm II++ M5 0.8 mm II + Mo 5mm II++ M5 Eroded nodule with milky-red veil and irregular vessels 1.5 mm II ++ M2 R +++ R, right; L, left; F, fingernail; T, toenail; LM, longitudinal melanonychia; II, inflammatory infiltration; M, mitosis; R, regression; U, ulceration.

170 Starace et al. 1 Left side 1 Right side 1 Figure 1 Tumor distribution in the different digits in our study. Figure 4 (a) Invasive nail melanoma of the I digit of right hand in a 43-year-old man, present for 1 year, presenting as a brown band of longitudinal melanonychia non-homogeneous with partial absence of nail plate in correspondence of the band and pigmentation of the hyponychium and the proximal nail fold (Hutchinson s sign). (b) Dermoscopy shows a longitudinal band with deep brown background, irregular lines in colour and thickness, interrupted along the length and blurred borders. The nail plate is partial absent in correspondence of the band. The Hutchinson s sign on dermoscopy shows diffuse brown pigmentation with a characteristic broad parallel ridge pattern in the periphery and irregularly distributed brown dots and depigmented areas. (c) Histological image showing invasive melanoma with Breslow thickness of 1 mm with inflammatory infiltration, 0 mitosis, regression and no ulceration. Figure 2 (a) Melanoma in situ of the III digit of right hand in a 38- year-old female, present for 1 year, presenting as a black band of LM 5 mm wide. (b) Dermoscopy shows a longitudinal band with black background, blurred borders and lines with variable colour, spacing and thickness, interrupted along the length. (c) Histological image showing an in situ nail apparatus melanoma with inflammatory infiltration, 0 mitosis, regression and no ulceration. Figure 3 (a) In situ melanoma of the II digit of left hand in an 18- year-old female, present for 1 years, presenting as a black-brown band of LM non-homogeneous. (b) Dermoscopy shows a longitudinal band with brown background, blurred borders, regular lines. (c) Histological image showing in situ melanoma with inflammatory infiltration, 0 mitosis, regression and no ulceration. Figure 5 (a) Amelanotic melanoma of the V digit of left hand in a 75-year-old man, appeared as a band of LM 20 years before and turned into a nodule 1 year before. Clinical image shows bleeding granulating mass of the nail bed involving the whole nail (a1) with Hutchinson s sign on the hyponychium (a2). (b) Dermoscopy of the nodule shows a white colour at the centre of the lesion and red colour at the periphery, irregular vessels with hairpin and kinky aspects and a milky-red veil (b1). Dermoscopy of the hyponychium shows brown pigmentation of the distal nail fold distributed in an irregularly mixed parallel ridge and furrow pattern with sparse black dots, white veil and depigmented area nearby the nail plate and some grey globules (b2). (c) Histological image showing invasive melanoma with Breslow thickness of 7 mm, with + inflammatory infiltration, 4 mitosis, ++ regression and ulceration.

Dermoscopy of nail apparatus melanoma 171 Table 2 Dermoscopic features in nail apparatus melanoma in our series Dermoscopic patterns Melanoma (n = 14) n (%) Amelanotic melanoma (n = 9), n (%) Total (n = 23) n (%) Blurred borders 12 (85.7) 0 (0) 12 (52.1) Regular borders 1 (1.7) 0 (0) 1 (4.3) Blurred/irregular lines 10 (71.4) 0 (0) 10 (43.4) Regular lines 2 (14.2) 0 (0) 2 (8.6) Lines interrupted along the length 5 (35.7) 0 (0) 5 (21.7) Lines with spacing 1 (7.1) 0 (0) 1 (4.3) Black dots 1 (7.1) 0 (0) 1 (4.3) Blood red spots/dots 1 (7.1) 0 (0) 1 (4.3) Nail plate changes 5 (35.7) 9 (100) 14 (60.8) Dotted and irregular vessels 0 (0) 4 (44.4) 4 (17.3) Vascular polymorphism 0 (0) 4 (44.4) 4 (17.3) Veil (milky-red, whitish) 1 (7.1) 8 (88.8) 9 (39.1) Irregular vessels 1 (7.1) 9 (100) 10 (43.4) Crusts 0 (0) 4 (44.4) 4 (17.3) Hutchinson s sign 4 (28.5) 2 (22.2) 6 (26) Micro Hutchinson s sign 0 (0) 2 (22.2) 2 (8.6) All the dermoscopic parameters analysed are reported in Table 2. Histopathology Sixteen of our 23 patients had invasive NAM, with a median Breslow thickness of 2.9 mm, and seven cases were in situ NAM. In invasive NAM, 12 cases of presented a Breslow thickness 1 mm and four cases <1 mm. The inflammatory infiltrate was evaluated as ++ in five patients; + in eight patients and was absent in nine patients, most of them were in situ NAM. The number of observed mitoses varied according to the tumour invasion: 10 patients did not present any mitosis, and most of them were in situ NAM. In the other 13 patients different number of mitosis were counted: less than two mitosis in five patients, and more than two in the other ones. The highest number of mitoses 15 were present in one case of amelanotic nail melanoma of the first digit of the hand, lasting for more than 3 years. Regression was evaluated as +++ in one patient, as ++ in six patients; as + in four patients and was absent in 12 melanomas. Ulceration was present in seven cases of invasive NAM while in the others was absent. On the basis of Breslow thickness, the thickest NAM was the amelanotic melanomas with the thickest in them being about 7 mm. This melanoma had been present as melanonychia from 20 years but in the last year the aspect changed quickly (Fig. 5). The six amelanotic melanomas with signs of regression had appeared many years before. In NAM presenting as solitary LM (six cases), without Hutchinson s sings or nail plate dystrophies the histological correlations, especially Breslow thickness, revealed frequently a melanoma in situ. These cases presented also a triangular shape of the band. The presence of LM was associated with nail plate surface alterations and sometimes with an almost complete destruction of nail plate (seven cases). These latter alterations (nail plate changes) correlate as follows with the Breslow thickness. The higher the nail plate damage was observed, the thicker was the tumour. The presence of Hutchinson s sign associated with the band of LM (four cases) was associated with a Breslow thickness reaching 2 mm (range 1 2 mm). The seven cases of amelanotic melanoma without Hutchinson s sign were invasive melanomas with a Breslow thickness raging from 1 to 6 mm, while in two cases of amelanotic melanoma with Hutchison s sign, the Breslow thickness reached 7 mm. Two patients with amelanotic melanoma associated with micro-hutchinson s sign had a NAM with a Breslow thickness of 0.8 mm. Discussion The early diagnosis of NAM, as for cutaneous melanoma is challenging for dermatologist. Nowadays, dermoscopy represents an important diagnostic tool that facilitates an early diagnosis of skin cancers and melanoma. Regarding the nail apparatus, LM is a common presentation of NAM, and in our experience the most frequent one. The classification of dermoscopic features of LM was well described in 2002 by Roger et al., 8 which showed that is suggestive for NAM a band of LM with brown to black background associated with longitudinal lines that are irregular in colour, width, spacing and/or parallelism. Our dermoscopic evaluation of 23 cases of histopathologically proven NAM observed in our Department suggests several conclusions:

172 Starace et al. Nail apparatus melanomas presenting as LMs accounts for 60% of the cases, but dermoscopic features suggestive for malignancy are found only in 4/5 of these bands, as the others 20% of the nail pigmentations show benign dermoscopic features. This suggests that the sole use of the Rongier s dermoscopic criteria is not sensitive enough to detect NAM. Three patients with NAM presenting as a band of LM with regular lines were in fact biopsied because the nail lesions followed the clinical criteria suggestive for NAM described by Levit in 2000 7 : a band involving a single digit, appeared in adulthood with no causes that could explain its onset. The clinical and dermoscopy parameters suggestive for NAM should therefore be utilized together. Nail apparatus melanoma presenting as a band of LMs not associated with Hutchinson or micro-hutchinson s sign and/or with nail plate changes was in our experience frequently NAM in situ. At this stage, complete removal of the nail apparatus could be the optimal surgical choice for the patient. 16 Micro Hutchison s sign, observed only by dermoscopy, is a very helpful feature for diagnosis of NAM. 17,18 Periungual pigmentation of hyponychium of periungual skin, evident only with magnifications >109 was seen in two of our patients with amelanotic melanomas and helped in dermoscopic differential diagnosis with other nail tumours. This is in our experience the most sensitive and specific use of dermoscopy in the diagnosis of NAM. The polymorphic vascular pattern is the most frequent feature seen in amelanotic melanoma, with milky-red areas and irregular vessels in the centre and blood spots and crusts at the periphery. 19 Differential diagnosis with eroded nodules due to benign of malignant nail bed tumours, such as squamous cell carcinomas or pyogenic granulomas, is however not possible with dermoscopy. These amelanotic variants were statistically correlated with a higher Breslow thickness and presented a worse prognosis. 9,20 Our data indicate that dermoscopic aspects of NAM may reflect the Breslow thickness, as periungual pigmentation, nail plate changes and the vascular pattern become more prominent in the invasive stage of NAM. In conclusion, we created an algorithm to indicate, step by step, the correct way to follow an adult patient with suspected NAM (Fig. 7). In case of LM, first of all, look at the nail plate and the periungual tissue to find any pigmentation visible by naked-eye and then with dermoscopy. If there is pigmentation, the diagnosis of melanoma is highly suggestive, and a biopsy is mandatory. Without periungual pigmentation the aspect of the pigmented band can direct the diagnosis. The most frequent aspect of NAM is irregular line pattern with brown to black background. Nail plate changes, indicative of nail matrix damage, are also suggestive for a malignancy. In case of a nail bed nodule with ulceration, its association with Hutchinson s sign is diagnostic for invasive NAM. The use of a dermatoscope may detect micro-hutchinson s sign and the irregular vascular structures with atypical vessels. All cases should indeed be biopsied. Figure 6 (a) Amelanotic melanoma of the I digit of right foot in an 86-year-old man, present for 2 years, presenting as an eroded nodule of the nail bed involving one-third of the nail. (b) Dermoscopy of the nodule shows a milky-red veil and vascular polymorphism. (c) Histological image showing invasive melanoma with Breslow thickness of 1 mm with ++ inflammatory infiltration, 1 mitosis, + regression and ulceration. Band of melanonychia Ulcer/Nodule Melanoma Probable melanoma With Hutchinson s sign Without Hutchinson s sign Dermoscopy Dermoscopy Background borders lines + age + history Micro Hutchinson sign Non melanoma With Hutchinson s sign Without Hutchinson s sign Without pigmentation Biopsy Melanoma Melanoma Figure 7 Suggested approach for diagnosis of nail apparatus melanoma.

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