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Clinical Updates

Toshiaki Saida, MD, PhD

Dermoscopic Detection of Melanoma on the Palms and Soles

Toshiaki Saida

Monday, July 30, 2012

The diagnostic technique of dermoscopy is widely used in the clinical evaluation of pigmented and non-pigmented skin lesions. Dermoscopic detection is particularly useful for the diagnosis of melanoma in pigmented lesions on the palms and soles.1

The most common melanoma, in non-white populations, affecting these anatomical sites is acral melanoma.2 Melanoma on the palms and soles shows a unique dermoscopic pattern called the parallel ridge pattern (PRP); this feature is diagnostically useful for differentiating early melanoma from benign pigmented lesions at these sites.3,4 In this article, the dermoscopic evaluation of melanoma and other pigmented lesions on the palms and soles is described.

Acral Melanoma on the Palms and Soles

Dermoscopic patterns characteristically observed in melanoma on the palms and soles include the PRP, which exhibits band-like pigmentation on the ridges of the surface skin markings (Figure 1a) and irregular diffuse pigmentation (IDP), which shows structureless pigmentation in variable shades of brown.4,5

The diagnostic sensitivity and specificity of the PRP are 86% and 99%, respectively, not only in invasive melanoma but also in in situ melanoma on the palms and soles.4 This highlights the importance of the PRP in distinguishing palmoplantar melanoma in its early stages, when the melanoma is more likely to be treated successfully.6

The specificity of IDP is comparable to that of the PRP. The sensitivity of IDP in invasive palmoplantar melanoma is also very high, at 97%. However, the sensitivity of IDP in in situ melanoma in lower than that of the PRP, at 69%.4 This means that IDP becomes more apparent in advanced lesions of palmoplantar melanoma.

In more advanced palmoplantar melanoma, many other dermoscopic findings seen in other subtypes of advanced melanoma are detected, such as irregular dots/globules, irregular streaks, regression structures, blue-white veil, and polymorphous vessels.3 However, an atypical pigment network is rarely found in palmoplantar melanoma.

 

Saida Fig 1

Figure 1. Representative dermoscopic patterns seen in melanocytic lesions on the palms and soles. The parallel ridge pattern (a) is characteristically detected in early melanoma. The parallel furrow (b), lattice-like (c), and (d) fibrillar patterns are major features observed in acquired melanocytic nevus on the palms and soles.

Melanocytic Nevus on the Palms and Soles

The majority of melanocytic nevi observed on the palms and soles are acquired nevi. Histopathologically, most of them are of junctional or compound type with a minor intradermal component. Major dermoscopic patterns seen in acquired melanocytic nevus on the palms and soles include the parallel furrow pattern (PFP), lattice-like pattern (LLP), and fibrillar pattern (FP) (Figure 1b-d).1,7

The PFP is distinguished by parallel linear or curvilinear pigmentation along the furrows of the skin markings.1 This pattern, observed in 50-60% of palmoplantar nevi, is the prototype of the three major dermoscopic patterns.7 In the LLP, transverse pigmented lines bridging the parallel pigmented lines of the PFP are seen, producing a lattice-like pigmentation pattern.1 This pattern is mainly detected in acquired nevi, located on the arch areas of the sole and peripheral portions of the palms and soles.8 The LLP is detected in approximately 15% of palmoplantar nevi.

The FP exhibits densely packed, fine fibrillar pigmentation, usually arranged in a direction crossing the skin markings.1 This pattern is caused by the oblique arrangement of the thick cornified layer resulting from mechanical pressure exerted through body weight.8 The incidence of the FP is variable among current studies, accounting for 6-21% of palmoplantar nevi.7 A combination of two or three of these major patterns is not uncommon because LLP and FP are anatomical or artifactual modifications of the PFP.7

In addition, dots/globules - mostly arranged on the ridges in a regular fashion - can be detected in melanocytic nevus on the palms and soles. It is worth noting that acral nevi located on the transitional zones between the glabrous and non-glabrous skin or on the interdigital areas occasionally show non-specific dermoscopic patterns, eg densely packed linear or reticular pigmentation. Histopathologically, these nevi on the transitional zones often exhibit random proliferation of melanocytes within the epidermis, mimicking the histopathologic features of melanoma.9 

Dermoscopic features of congenital nevus on the palms and soles are not essentially different from those of acquired nevus, with PFP being the most common feature.10 However, a few additional characteristic dermoscopic patterns are detected. One such pattern is the crista dotted pattern, which shows multiple globules arranged regularly on the ridges of the skin marking (Figure 2a).10 Another is the "peas in a pod" pattern consisting of the PFP and the crista dotted pattern (Figure 2b).10 In addition, rather diffuse grayish blue pigmentation can be detected in congenital palmoplantar nevus, reflecting the predominant intradermal component commonly seen in congenital nevus.

Saida Fig 2

Figure 2. Dermoscopic patterns seen in congenital melanocytic nevus on the palms and soles: (a) the crista dotted pattern and (b) the peas in a pod pattern.

Other Pigmented Lesions Showing the PRP or Similar Patterns

The PRP is a useful dermoscopic finding for detecting early melanoma on the palms and soles. However, several conditions other than melanoma also show the PRP or similar patterns on dermoscopy.11,12 For example, pigmented macules on the digits in Peutz-Jeghers and Laugier-Hunziker syndromes exhibit the PRP.13 These syndromes can be correctly diagnosed by their characteristic clinical features such as multiple small macules on multiple digits and on the lip. The PRP can also be detected in palmoplantar pigmentation induced by drugs such as 5-fluorouracil, or in volar melanotic macules mainly seen in black persons.11 Pigmented ridged warts also shows dermoscopic features mimicking the PRP.14 This type of wart must be carefully differentiated from the rare verrucous type of acral melanoma.15

Dermoscopic features of hemorrhage or hematoma on the palms and soles are essentially the same as those seen in lesions on non-glabrous skin, ie bluish-red or reddish-black homogeneous areas. However, subcorneal hemorrhage in the acral skin sometimes demonstrates a pebble-like appearance or band-like pigmentation on the ridges of the skin markings, mimicking the PRP.11 Sharp demarcation and a reddish hue of the pigmentation are differentiating features from the authentic PRP. The PlayStation purpura, ie subcorneal purpura of the fingers induced by repetitive friction with the controller of computer game devices, also shows PRP-like pigmentation.16 Accidental staining of the palmoplantar skin with a foreign body, such as paraphenylendiamine or  self-tanning products, could also cause the PRP-like pigmentation.12

A Three-Step Algorithm for the Detection of Melanoma on the Palms and Soles

Our study group has proposed a three-step algorithm for the management of acquired melanocytic lesions on the palms and soles,17 based on our dermoscopic data and the 7 mm criterion we proposed previously.18 This algorithm is shown in Figure 3.

Saida Fig 3

Figure 3. A three-step algorithm for the management of acquired melanocytic lesions on the palms and soles. Reproduced with permission from Tanioka M et al. Clin Exp Dermatol. 2009;34:41-44.11

One possible problem with this algorithm could be in the evaluation of the regularity of the FP in the second step. Overall, symmetric distribution of the fibrillar pigmentation is important in the judgment of regular FP. Another indication of the regular FP is that starting points of the fibrillar pigmentation are mostly arranged in a linear fashion, corresponding to the furrows of the skin marking.11

We expect that, by using this algorithm, most palmoplantar melanomas will be detected effectively in the early curable stages and the number of unnecessary excision of benign nevi substantially reduced.17

Conclusions

Using dermoscopy, we can effectively detect early melanoma on the palms and soles based on the finding of the PRP, which differs completely from the findings seen in melanocytic nevus at these sites. Although several pigmented lesions on the palms and soles can show the PRP or similar patterns, they are easily differentiated from melanoma upon careful clinical and/or dermoscopic evaluation.

References

  1. Ishihara K, Saida T, Otsuka F,et al. Statistical profiles of malignant melanoma and other skin cancers in Japan: 2007 update. Int J Clin Oncol.  2008;13:33-41.
  2. Oguchi S, Saida T, Koganehira Y,et al. Characteristic epiluminescent microscopic features of early malignant melanoma on glabrous skin: a videomicroscopic study. Arch Dermatol.  1998;134:563-568.
  3. Saida T, Miyazaki A, Oguchi Set al. Significance of dermoscopic patterns in detecting malignant melanoma on acral volar skin: results of a multicenter study in Japan. Arch Dermatol. 2004;140:1233-1258.
  4. Kawabata Y, Tamaki K. Distinctive dermoscopic features of acral lentiginous melanoma in situ from plantar melanocytic nevi and their histopathologic correlation. J Cutan Med Surg.  1998;2:199-204.
  5. Ishihara Y, Saida T, Miyazaki A,et al. Early acral melanoma in situ: correlation between the parallel ridge pattern on dermoscopy and microscopic features. Am J Dermatopathol.  2006;28:21-27.
  6. Saida T, Koga H. Dermoscopic patterns of acral melanocytic nevi: their variations, changes, and significance. Arch Dermatol. 2007;143:1423-1426.
  7. Miyazaki A, Saida T, Koga H,et al. Anatomical and histopathological correlates of the dermoscopic patterns seen in melanocytic nevi on the sole: a retrospective study. J Am Acad Dermatol. 2005;53:230-236.
  8. Saida T, Kawachi S, Koga H. Anatomical transition and the histopathologic features of melanocytic nevi. Arch Dermatol. 2008;1444:1232-1233.
  9. Minagawa A, Koga H, Saida T. Dermoscopic characteristics of congenital melanocytic nevi affecting acral volar skin. Arch Dermatol. 2010;147:809-813.
  10. Saida T, Koga H, Uhara H. Key points in dermoscopic differentiation between early acral melanoma and acral nevus. J Dermatol. 2011;38:25-34.
  11. Tanioka M, Matsumura Y, Utani A, et al. Occupation-related pigmented macules on the sole with parallel-ridge pattern on dermoscopy. Clin Exp Dermatol. 2009;34:41-44.
  12. Sendagorta Cudos E, Feito Rodriguez M, Ramirez Marin P,et al. Dermoscopic findings and histopathological correlation of the acral volar pigmented maculae in Laugier-Hunziker syndrome. J Dermatol. 2010;37:980-984.
  13. Arpaia N, Filotico R, Mastrandrea V,et al. Acral viral wart showing a parallel ridge pattern on dermoscopy. Eur J Dermatol. 2009;19:381-382.
  14. Dalmmau J, Abellaneda C, Puig S,et al. Acral melanoma simulating warts: dermoscopic clues to prevent missing a melanoma. Dermatol Surg. 2006;32:1072-1078.
  15. Robertson S, Leonard J, Chamberlain AJ. PlayStation purpura. Australas J Dermatol. 2010;51:220-222.
  16. Koga H, Saida T. Revised 3-Step dermoscopic algorithm for the management of acral melanocytic lesions. Arch Dermatol. 2011;147:741-743.
  17. Saida T, Yoshida N, Ikegawa S,et al. Clinical guidelines for the early detection of plantar malignant melanoma. J Am Acad Dermatol. 1990;23:37-40.
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