10.5826/dpc.1203a123
text/xml
2160-9381
1813
en
Hisashi Uhara
https://creativecommons.org/licenses/by-nc/4.0
Dermatology Practical & Conceptual
dermoscopy, early acral melanoma, acral nevus, 3-step algorithm, regular and irregular fibrillar pattern
Dermoscopy for acral melanocytic lesions: Revision of the 3-step algorithm and refined definition of the regular and irregular fibrillar pattern
Text.Serial.Journal
https://dpcj.org/index.php/dpc
Commentary
2022-07-28
2021-05-27
2022-07-28
2022-09-14
e2022123
Dermatol Pract Concept
Hisashi Uhara
2022/07/28
10.5826/dpc.1203a123
e2022123
Department of Dermatology, Sapporo Medical University School of Medicine, Sapporo, Japan
2160-9381
dermoscopy, early acral melanoma, acral nevus, 3-step algorithm, regular and irregular fibrillar pattern
en
e2022123
Dermoscopy for acral melanocytic lesions: Revision of the 3-step algorithm and refined definition of the regular and irregular fibrillar pattern
https://dpcj.org/index.php/dpc/article/download/1813/1699
                    Dermatology Practical & Conceptual


Dermoscopy for Acral Melanocytic Lesions: Revision
 of the 3-step Algorithm and Refined Definition of
     the Regular and Irregular Fibrillar Pattern
                                   Toshiaki Saida1, Hiroshi Koga1, Hisashi Uhara2


1 Department of Dermatology, Shinshu University School of Medicine, Matsumoto, Japan
2 Department of Dermatology, Sapporo Medical University School of Medicine, Sapporo, Japan



Citation: Saida T, Koga H, Uhara H. Dermoscopy for acral melanocytic lesions: Revision of the 3-step algorithm and refined definition of
the regular and irregular fibrillar pattern. Dermatol Pract Concept. 2022;12(03):e2022123. DOI: https://doi.org/10.5826/dpc.1203a123
Accepted: October 26, 2021; Published: July 2022
Copyright: ©2022 Saida et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 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: Toshiaki Saida, MD, PhD, Shinshu University, Matsumoto; Kamiochiai 7-7-40-220, Chuo-ku, Saitama 338-0001,
Japan. E-mail: tosaida@xb4.so-net.ne.jp




Acral melanoma (AM) is the most prevalent subtype of                     The 3-step Algorithm and its
malignant melanoma in non-white populations. It is often
                                                                         Re-revision
detected in advanced stages, resulting in poor prognosis.
However, the prognosis is favorable if detected in the early             Based on these characteristic dermoscopic findings, in 2007
stages; almost all the patients with AM in situ are cured                our group proposed a dermoscopic 3-step algorithm for the
only by surgical excision with a narrow margin. Thus, early              management of acral melanocytic lesions [3] and then, re-
detection is essential in the management of AM. Although                 vised it in 2011 [4]. Recently, several studies were reported
clinical differentiation between early AM and acral nevus                which examined utility of the 3-step algorithm [5-7]. In these
is sometimes very difficult, dermoscopy is highly helpful in             studies, the 3-step algorithm generally worked well, how-
the differentiation [1]. A commonly detected, specific der-              ever, in one study, the algorithm missed one lesion of AM,
moscopic pattern of early AM is the parallel ridge pattern               0.5 mm in Breslow thickness. The lesion, 6 mm in diame-
(PRP), exhibiting band-like pigmentation on the surface                  ter, did not show the PRP but exhibited a multicomponent
ridges of the skin markings (dermatoglyphics) [2]. In con-               pattern. Considering rather lower sensitivity of the PRP in
trast, the main dermoscopic pattern of acral nevus is the                AM of their case series, Lallas et al proposed the BRAAFF
parallel furrow pattern (PFP) showing linear pigmentation                checklist for the effective detection of AM, which included
along the sulci of the skin markings. Other dermoscopic pat-             irregular blotch and asymmetry of structures and colors as
terns frequently observed in acral nevus are the lattice-like            positive features [8]. These findings along with our further
pattern and the fibrillar pattern (FP), both being modifica-             experience prompted us to re-revise the 3-step algorithm as
tions of the PFP [3].                                                    shown in Figure 1. This version includes a multicomponent




Commentary | Dermatol Pract Concept. 2022;12(03):e2022123                                                                                  1
                                                                      ACQUIRED MELANOCYTIC LESIONS
                                                                      ON ACRAL VOLAR SKIN


                                                                     PARALLEL RIDGE PATTERN (PRP)
 FIRST STEP                                                                      OR
                                                                 ASYMMETRIC MULTICOMPONENT PATTERN


                                                                        NO                       YES


                                       TYPICAL PARALLEL FURROW PATTERN,
                                            LATTICE-LIKE PATTERN OR
 SECOND STEP
                                           REGULAR FIBRILLAR PATTERN

                                             YES                 NO



                                                                             MAXIMUM DIA-
 THIRD STEP                                                                  METER, > 7 mm

                                                                         NO             YES



 MANAGEMENT             NO NEED OF FOLLOW-UP                   FOLLOW-UP                 BIOPSY FOR HISTOPATHOLOGIC EVALUATION



                                                   ENLARGE TO > 7 mm, OR
                                                   APPEARANCE OF PRP OR ASYMMETRIC
                                                   MULTICOMPONENT PATTERN


 Figure 1. The re-revised 3-step algorithm for the management of melanocytic lesions on acral volar skin. The main targets of this algo-
 rithm are macular/patch lesions seen in adults. Apparently congenital lesions and nodular lesions are excluded from the evaluation.




pattern in the first step as well as a follow-up strategy after       Criteria for Regular and Irregular Fibrillar
the third step.                                                       Pattern and Clues to the Management
    One possible problem in using the 3-step algorithm is             Herein, based on our experience, we refine the definitions of
judgment of whether the FP is regular or irregular. Accord-           the “regular” and “irregular” FP, and then write down sev-
ing to Costello et al, physicians often did not recognize the         eral clues which help us in the management of acral lesions
regular FP as a benign pattern [6]. The FP is characterized           showing the FP. The oblique dermoscopy [12] and the furrow
by densely packed brownish fibrillar lines arranged in a par-         ink test [13. 14] are very helpful in the evaluation of the FP.
allel fashion and crossing the skin markings. Each fibril of
the pattern corresponds to a melanin column in the thick
                                                                      Regular FP of acral nevus
cornified layer which is obliquely arranged due to the me-
                                                                      The fibrils constituting the regular FP are evenly distributed
chanical pressure from the body weight. This is the reason
                                                                      throughout the lesion and mostly same in color and thick-
for the predilection of nevi of this pattern for the pressured
                                                                      ness (Figure 2A). The endpoints (deeper color ends) of the
areas of the sole [9]. Thus, the FP is regarded as an artifactual
                                                                      fibrils tend to line up on the sulci of the skin markings. In
expression of the PFP [1, 3]. Noteworthy is that the FP is
                                                                      addition, not infrequently, the FP is combined with the PFP
occasionally found focally within a lesion of AM [1]. This is
                                                                      and/or changes to the PFP at the periphery. In most cases, the
not strange because, as mentioned above, the FP is detected
                                                                      oblique dermoscopy demonstrates that the FP is originally
in the pressured areas of the sole, which are the most preva-
                                                                      the PFP (Figure 2B).
lent subsite of AM. Moreover, the FP can occupy an almost
entire lesion of AM in situ, particularly in its early evolving
stages [10,11]. This could lead us to misdiagnosis of AM in           Irregular FP of acral melanoma
situ as acral nevus. Hence, it is very important for us to cor-       The fibrils constituting the irregular FP are unevenly distrib-
rectly differentiate the FP of early AM in situ from that of          uted and variable in color and thickness (Figure 3). In most
acral nevus.                                                          cases, the endpoints of the fibrils are arranged randomly.



2                                                                            Commentary | Dermatol Pract Concept. 2022;12(03):e2022123
                Figure 2. Regular fibrillar pattern of acral nevus (dermoscopy with the furrow ink test). (A) The fibrils con-
                stituting the pattern are regular in color, thickness and distribution. All the endpoints of the fibrils line up on
                the sulci of the skin markings. The pattern changes to the parallel furrow pattern in the lower portion. (B) The
                oblique dermoscopy reveals that this is originally the parallel furrow pattern.




In some lesions, however, they are located within the width                   crossing the surface ridges but uninvolving the sulci
of the ridges of the skin markings. Moreover, the PRP is not                  (Figure 4). This finding may be misinterpreted as the
infrequently detected at least focally within a lesion. By the                “regular” FP. But it does not change to the PFP on
oblique dermoscopy, the irregular FP does not change to the                   oblique dermoscopy. Such a lesion should be biopsied
PFP but, though rarely, to the PRP [10].                                      or carefully followed, particularly when seen in elderly
   In addition to the aforementioned criteria, there are sev-                 persons. In our case series, this “regular” FP was ob-
eral findings which are helpful when we manage acral lesions                  served in 2 out of 10 lesions of AM in situ showing the
showing the FP. They are summarized as follows.                               FP [16].
                                                                          4. If the fibrils composing the FP is thick and regular in
1. If, in a lesion of the FP, non-site specific dermoscopic find-             color, the lesion is certainly diagnosed as acral nevus, par-
   ings of melanoma (eg irregular streaks, irregular dots/glob-               ticularly when the lesion is small, ie, less than 5 mm in
   ules, irregular blotches, blue-white veils, and/or regression              diameter (Figure 5).
   structures) are detected, the lesion should be treated as AM.          5. When we cannot determine whether the FP is regular
2. Acral lesions exhibiting the negative fibrillar pattern should             or irregular, periodic follow-up of the lesion is recom-
   be biopsied for histopathologic evaluation (Figure 3). This                mended, with a frequency of once or twice a year.
   pattern consists of whitish rods arranged in a parallel fash-
   ion on the dark structureless or fibrillar background [15].                It is widely accepted that dermoscopy is quite helpful in
   The whitish rods represent intracorneal eccrine ducts. In              the evaluation of pigmented lesions on acral volar skin. We
   our recent study of acral nevi (41 lesions) and AM in situ             believe the re-revised 3-step algorithm and refined criteria
   (10 lesions), the sensitivity and specificity of this finding for      for the regular and irregular FP described in this commen-
   AM in situ were 40% and 90%, respectively [16].                        tary will further assist clinicians in managing acral mela-
3. A very early lesion of AM in situ could show the FP                    nocytic lesions appropriately, though their validity must be
   entirely composed of densely packed very thin fibrils                  evaluated in larger case series.



Commentary | Dermatol Pract Concept. 2022;12(03):e2022123                                                                                3
    Figure 3. Irregular fibrillar pattern of acral melanoma in situ. This lesion of the multicomponent pattern is mostly composed of fibrils
    and can be regarded as the irregular FP by our definition, ie, the fibrils constituting the pattern are irregular in color, thickness and distri-
    bution, and their endpoints do not line up on the sulci of the skin markings. (A) Transition to the parallel ridge pattern is detected in the
    right lower portion. The negative fibrillar pattern (whitish rods arranged in a parallel fashion) are detected in the left area, which is well
    recognized in (B), an image of higher magnification corresponding to the square area in (A). (B) Arrows indicate some of the whitish rods.




Figure 4. “Regular” fibrillar pattern seen in acral melanoma in situ (A, inset: clinical features: a brown patch, 13.5 × 10.5 mm in size, seen on the
sole of a 78-year-old woman). (A) The very thin fibrils constituting this fibrillar pattern are evenly arranged and regular in color and thickness.
(B) the square area in (A). The furrow ink test reveals that the sulci of the skin markings, indicated with arrows, are spared from the fibrillar pig-
mentation. (C, D) Histopathological features. (D) corresponds to the square area in (C). The thick cornified layer is obliquely arranged, as indicated
with arrows in (C). The increased number of melanocytes are mainly detected in the crista profunda intermedia indicated with asterisks in (C)
and their nuclei are large and hyperchromatic as seen in (D), confirming this is acral melanoma in situ. (Note: FISH analysis of this lesion revealed
amplification of cyclin D1.)


4                                                                                   Commentary | Dermatol Pract Concept. 2022;12(03):e2022123
Figure 5. Regular fibrillar pattern composed of thick fibrils. A small brown macule, 4 mm in diameter, seen on the sole of a 38-year-old
woman. This fibrillar pattern is composed of regularly arranged thick fibrils, of which endpoints line up on the sulci of the skin markings.
Although the color density of the fibrils is somewhat different within the lesion, the color distribution is mostly symmetric, indicating this is
the regular FP. From these findings, we can certainly diagnose this lesion as acral nevus. Note: These thick fibrils indicate that melanocytes in
the epidermis are not distributed as solitary units but arranged mostly in larger nests, which is an important histopathologic clue to benign
nevus of a small size such as this one (4mm).




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