Introduction
Mycosis fungoides (MF) is the most frequent cutaneous T-cell lymphoma (CTCL). It accounts for about 62% of all CTCLs and almost 50% of all primary cutaneous lymphomas (PCLs) [1, 2]. The diagnosis of MF is based on clinicopathological correlation in combination with immunophenotype and molecular results of T-cell receptor (TCR) clonality [2, 3]. Diagnosis of MF is a challenge, due to several reasons. Firstly, MF presents in many different subtypes. Although WHO-EORTC classification distinguishes only three MF variants, i.e. folliculotropic, granulomatous slack skin and pagetoid reticulosis, many other rare variants are described in the literature [4–9]. Secondly, it has been described that MF can mimic over 50 various dermatoses (inflammatory and non-inflammatory) [6]. Furthermore, even histologic examination of MF lesions can be indistinguishable from inflammatory skin diseases. For example, classic histopathological signs, including epidermotropism, atypical lymphocytes and Pautrier's (now properly called Darier's) microabscesses may not be present in the early stage of the disease, on the other hand, these findings can also be seen in other inflammatory skin diseases [10]. Adding to that, regular use of topical glucocorticoids or other immunosuppressants may diminish both clinical and histological features suggestive of mycosis fungoides [10]. All these difficulties contribute to the delay of the final diagnosis by an average of 3 years [11]. Dermoscopy and trichoscopy are non-invasive skin imaging tools, commonly used in daily dermatological practice [12]. Unfortunately, data about their usefulness in mycosis fungoides are scant, and based mostly on case series and case reports. There are few case-control studies, which mainly concentrated on comparing early-stage classic MF with other dermatoses such as psoriasis and eczema. Spermatozoa-like structures and orange-yellowish patchy areas were usually linked to MF [13–17]. The largest retrospective observational study was performed by the International Dermoscopy Society in 2022 and included 118 patients with MF (75 classic, 26 folliculotropic, 9 erythrodermic, and 8 poikilodermatous). They compared different stages of classic MF and revealed that linear/linear-curved vessels and white scales in the skin furrows were mainly associated with patches, dotted vessels in clusters with plaques, while peripheral linear vessels with branches, ulceration and red globules separated by white lines were associated with tumors. The most common dermoscopic features regarding folliculotropic MF were lack of hairs, dilated follicles and follicular plugs [18].
The aim of this article is to evaluate the role of dermoscopy and trichoscopy in the diagnosis of different variants of mycosis fungoides based on the literature review.
Methods
A thorough literature review of dermoscopic and trichoscopic features in different variants of mycosis fungoides was conducted by searching PubMed, Scopus, and EBSCO databases, using results up to August 2023. The following search terms were employed: “mycosis fungoides”, “MF”, “cutaneous lymphoma”, and “CTCL”, combined with “dermoscopy”, “dermatoscopy”, or “trichoscopy”. Additionally, the references of all eligible articles were reviewed to identify further relevant publications. Original studies, case series and case reports considering the frequency of dermoscopic and trichoscopic features in mycosis fungoides were eligible for the analysis. Publications with incomplete epidemiological data, animal studies, reviews, or non-English language articles were excluded.
A qualitative analysis regarding dermoscopic and/or trichoscopic features of classic, erythrodermic, folliculotropic, syringotropic, pagetoid reticulosis, granulomatous slack skin, poikilodermic, purpuric, telangiectatic, hypopigmented, verrucous and developing in the scar variant of mycosis fungoides was performed.
Furthermore, based on 9 case-control studies [9, 13–20], a quantitative analysis regarding dermoscopic features of classic mycosis fungoides was performed. The studies are shown in table 1.
In the selected studies, different methods of describing dermoscopic features were used (metaphoric and descriptive). We classified them into similar groups and, if it was possible, named them accordingly to standardized dermoscopic terminology provided by the International Dermoscopy Society [21]. Only features that were reported in at least 3 articles were taken into consideration. The sensitivity, specificity, positive and negative predictive values of the most characteristic dermoscopic findings were calculated based on the studies in which that particular dermoscopic feature was assessed. The exact review process is shown in figure 1.
Results
A total number of 47 articles (15 original studies, 7 case series, 25 case reports) was included in the qualitative analysis. Dermoscopic features were reported in 34 articles, trichoscopic features in 10 articles, while 3 articles concerned both dermoscopy and trichoscopy.
The classic variant of mycosis fungoides was assessed in 11 articles (dermoscopy 10; trichoscopy 1), erythrodermic MF in 5 articles (dermoscopy 2, trichoscopy 2, dermoscopy and trichoscopy 1), folliculotropic variant in 19 articles (dermoscopy 10, trichoscopy 7, dermoscopy and trichoscopy 2), syringotropic variant in 1 article, pagetoid reticulosis in 5 articles, granulomatous slack skin in 2 articles, poikilodermic variant in 7 articles, purpuric variant in 1 article, telangiectatic variant in 1 article, hypopigmented variant in 1 article, verrucous variant in 1 article, and developing in the scar variant in 1 article. The evolution of mycosis fungoides was described in 3 articles.
Quantitative analysis based on the 9 original studies revealed the most common and the most specific dermoscopic features of the classic variant of mycosis fungoides. The results of the quantitative analysis are shown in table 2 and described below.
Dermoscopy of classic mycosis fungoides
The systematic review revealed five most common dermoscopic features with sensitivity ³ 50%. These include: linear vessels (66.1% sensitivity), white scales (60.1% sensitivity), orange-yellow focal structureless areas (59.2% sensitivity), dotted vessels (57.8% sensitivity) and dull red background color (55.2% sensitivity). We also found six most specific dermoscopic features of classic mycosis fungoides with specificity ³ 80%. There are linear curved vessels (95.6% specificity), linear vessels with branches (91.3% specificity), linear vessels (88.2% specificity), orange-yellow focal structureless areas (87.6% specificity), purple dots/globules (82.1% specificity) and white focal structureless areas (80.0% specificity). Two features, linear vessels and orange-yellow focal structureless areas, are particularly important as they show high sensitivity (66.1% and 59.2%, respectively) as well as specificity (88.2% and 87.6%, respectively). These dermoscopic features are presented in figure 2.
Other interesting dermoscopic features of classic mycosis fungoides, which were not included in the quantitative analysis, are presented in table 2 and include red globules separated by white lines, ulceration, crystalline structures, rosettes, and perivascular halos [9, 13, 18, 20].
Red globules separated by white lines were reported by Errichetti et al. in 2022 in 4/28 patients with tumoral mycosis fungoides. They were not observed in patch or plaque MF. They are thought to correspond to multinodular lymphomatous cellular infiltration of the dermis, which can be present in tumoral MF [18]. Ulceration corresponding to the loss of epidermis histologically, was described in 6/28 patients with tumoral mycosis fungoides and was not reported in patch or plaque MF [18].
Crystalline structures were reported in 2 patients with patch MF [13], rosettes in 7 patients [9] and perivascular halo in 3 patients with classic MF [20].
Dermoscopy of classic mycosis fungoides in patients with skin of color was described only in 4 patients. The reported features significantly varied from the ones mentioned above. They included striking pigmentary changes with pseudonetworks made of brown-gray or black clods and dots, as well as thick black lines and geometric white lines on erythematous/whitish pink structureless areas, interrupted by prominent eccrine duct openings and white rosettes [22].
Finally, it is worth mentioning that in 2023, Kamińska-Winciorek et al. described an evolution of mycosis fungoides in 3 patients after allogenic hematopoietic stem cell transplantation (alloHSCT), which, potentially is the only curative therapy. A change of the background color from red-orange/red-purple to skin-colored/light brown and the disappearance of linear and dotted vessels were described as a marker of disease remission. Conversely, persistence of linear vessels and new dotted vessels were observed in progression of the disease. White diffuse structureless areas, brown lines and globules did not correspond to the disease status [23].
Trichoscopy of classic mycosis fungoides
In classic mycosis fungoides, the head is usually unaffected and follicles remain unchanged [24, 25]. Trichoscopy was only described by Rudnicka et al. in the Atlas of Trichoscopy in 2012. Trichoscopic features included milky-red globules surrounded by normal-appearing skin, orange-yellow patchy areas, serpentine-like blood vessels, dotted vessels and decreased number of follicular units [26].
Dermoscopy of erythrodermic mycosis fungoides
Erythrodermic mycosis fungoides affecting ³ 80% of the skin surface, is usually considered as a progression of mycosis fungoides [8, 27]. Dermoscopy was described in 3 articles, namely 2 original studies [18, 28] and 1 case series [29], with a total number of 19 patients with erythrodermic mycosis fungoides. In a study by Errichetti et al. [18], both dotted and linear vessels were found in 77.8% of patients, linear curved vessels in 44.4% of patients, white patchy scales as well as focal orange structureless areas in 66.7% of patients, and focal brown structureless areas in 44.4% of patients. These features were compatible with patch-stage classic mycosis fungoides [18].
In a study by Sławińska et al. [28], the most common dermoscopic features, observed in all patients (9/9) included white patchy scales, white-pinkish structureless areas, dotted and linear vessels (including linear irregular and spermatozoa-like ones). Brown structureless areas were present in 77.8% of patients. In comparison, orange-yellowish patchy areas, which are common in classic mycosis fungoides, were present in only 1 patient [28].
In a case report [29], similar dermoscopic features were described, including dotted vessels, spermatozoa-like vessels, white scales, and white-pinkish background.
Trichoscopy of erythrodermic mycosis fungoides
Trichoscopic features of erythrodermic mycosis fungoides have been described in 3 articles: 2 original studies [28, 30] and 1 case report [31], comprising a total of 17 patients with erythrodermic MF. In a study by Sławińska et al. [28] the most common trichoscopic features included white interfollicular scales and white-pinkish structureless areas (each found in 66.7% of patients). Dotted vessels and linear vessels (including linear irregular and spermatozoa-like ones) were both present in 55.6% of patients. Interestingly, they were more frequent in dermoscopic examination, and were observed in all patients. A new trichoscopic feature, flesh-colored circles around the hair follicles containing blood vessels with radial or concentric arrangement, was first described in this study in 2 patients [28]. The most common trichoscopic features reported by Golińska et al. [30] included a white-pinkish background and interfollicular white scales, both present in all patients, as well as dotted vessels, short linear irregular vessels, and spermatozoa-like vessels with an irregular distribution. In a case report by Miteva et al. [31], a patient with subtotal alopecia was described. On trichoscopic examination, diffuse erythema, empty follicular openings filled with keratotic plugs or filiform spicules and few terminal hairs with peripilar white casts were detected [31].
Dermoscopy of folliculotropic mycosis fungoides (FMF)
The folliculotropic variant accounts for about 10% of mycosis fungoides cases and is presumed to be the more aggressive subtype. Toncic et al. in 2018 recognized perifollicular accentuation (white perifollicular halo) as an early dermoscopic marker of folliculotropism in a histopathologic examination [25]. Then again, Wang et al. (2021), in a strikingly similar article, identified yellow globules (accompanied by sparsely distributed fine, short linear vessels at their periphery and loss of normal hair follicle architecture) as an early dermoscopic marker of folliculotropism confirmed by histopathologic examination [32]. The sizes of the white perifollicular halos and yellow globules vary and correlate with the amount of lymphoid infiltrate and/or mucin deposits [25, 32]. Perifollicular accentuation was found in patients without evident clinical symptoms of FMF, therefore it can be chosen as a biopsy site [25]. The International Dermoscopy Society evaluated the most common dermoscopic features based on 26 patients with FMF, which currently remains the largest study. They reported features such as lack of hairs (92.3%), dilated follicles (80.8%), follicular plugs (61.5%), white scales (42.3%), follicular red dots (30.8%) and perifollicular white color (30.8%) [18]. Other studies and case reports detected similar features, including perifollicular accentuation, lack of hairs, comedo-like openings/keratotic plugs, folliculocentric erosions, white structureless areas, white scales, fine short linear and dotted vessels [11, 13, 33–35]. Comedo-like openings/keratotic plugs correspond to the follicular plugging and destruction of hair follicles [13]. In a study by Elloudi et al. [9], the most frequent dermoscopic findings for FMF were similar to classic MF, including dotted vessels, white scales, orange-yellowish patchy areas and rosettes (however dermoscopic features typical for FMF were probably not assessed). Dermoscopy in dark-skinned patients with FMF was assessed in 2 patients and in both revealed hyperpigmented perifollicular halos [22, 36]. In a dermoscopic examination of a spiky form of folliculotropic mycosis fungoides, which is a very rare manifestation, multiple keratotic, cone-shaped spicules surrounding follicular openings were visualized [37].
Trichoscopy of folliculotropic mycosis fungoides
The scalp is frequently affected in folliculotropic mycosis fungoides, which can lead to alopecia in about 65% of patients as patchy (72.2%) or generalized form (27.8%). Non-scarring alopecia is more common, while scarring alopecia can be linked to more advanced stages of the disease. Trichoscopy of folliculotropic mycosis fungoides was investigated in only 1 original article, other descriptions come from 8 case reports. The first trichoscopic feature, comedonal lesions, was reported by Trueb et al. [26] in 2012, in the Atlas of Trichoscopy. Gallo et al. [38] performed a study on 18 patients with FMF and presented six most common trichoscopic features: single hairs (83.3%), dotted dilated vessels (77.8%), broken, dystrophic hairs (66.7%), vellus hairs (61.1%), spermatozoa-like pattern vessels (55.6%), and yellow dots (55.6%). Additional features included dilation of follicular openings, scales/crusts, purpuric dots, short hair with split-end, pigtail hairs, perifollicular hyperkeratosis, milky-white globules, black dots, white dots/lines and absence of follicular dots. Pigtail hairs, yellow dots and spermatozoa-like vessels were indicative of the early-stage disease, while white dots and absence of follicular dots suggested an advanced stage of the disease. Sławińska et al. [39] reported a variety of trichoscopic features detected in 1 patient: decreased number of pilosebaceous units, mostly single hairs, milky-white globules, yellow dots with or without centrally located black dots/broken hairs, short hairs with split-end or with triangular-shape end, pigtail hairs, short hairs broken at the same/different level, white dots and lines, white and yellow scale. Iorizzo et al. [40] reported reddish, dilated follicular openings filled with sebokeratotic material, surrounded by white halos, lack of terminal hairs, broken hairs, pili torti and polymorphous vessels. Geller et al. [34] reported perifollicular halos and broken hairs while Manaa et al. [41] reported a decreased number of pilosebaceous units, white scales, erythematous background, and fine linear vessels. Kreutzer and Effendy [42] presented a patient with scarring alopecia due to folliculotropic mycosis fungoides and found comedonal lesions and loss of the adnexal structures in the trichoscopic examination. There are 2 case reports that describe trichoscopy in the spiky form of folliculotropic mycosis fungoides. These trichoscopic features include thick coats of keratinaceous debris around dilated openings [37] and follicular keratotic lesions [43]. Furthermore, a dermoscopic and trichoscopic resolution of keratotic spicules (on the scalp and the upper back) after
6 months of chemotherapy was reported [37].
Dermoscopy of syringotropic mycosis fungoides
Syringotropic mycosis fungoides is a very rare form of the disease. It is classified as a subtype of folliculotropic mycosis fungoides with an infiltration of both hair follicles and eccrine glands. Dermoscopic features of syringotropic mycosis fungoides were described in only 2 patients and they were identical to those found in the folliculotropic variant (obliteration of the follicles, follicular accentuation, follicular plugging, loss of terminal follicles, comedo-like openings, and interconnected structureless patches). However, one new feature was discovered in a patient with more prominent eccrine involvement, i.e. bluish structures with unsharp borders. Such structures were not reported in folliculotropic mycosis fungoides, but can be found in other eccrine tumors [44].
Dermoscopy of pagetoid reticulosis
Pagetoid reticulosis is a rare variant of mycosis fungoides characterized by intraepidermal pagetoid spread of atypical lymphocytes. It usually follows an indolent course with skin lesions limited to the distal extremities (Woringer-Kolopp disease), however there is also a generalized form (Ketron-Goodman disease) with a more aggressive course [45]. Dermoscopy of pagetoid reticulosis was described in 5 case reports [46–50]. The most common dermoscopic pattern included dotted/glomerular vessels, whitish scales, homogenous pinkish background and whitish negative network at the periphery of the lesion [48–50]. Similar features were detected by Manoli et al. [47] including regularly distributed dotted/glomerular vessels, pinkish background, diffuse hyperkeratosis with white scales and also coalescent whitish halos with a central red dot. Di Meo et al. [46] reported a central pinkish area, segmental brown radial lines and a large scaly circular peripheral border with linear vessels.
Dermoscopy of granulomatous slack skin
Granulomatous slack skin (GSS) is an extremely rare variant of mycosis fungoides. The disease follows an indolent course, however, it may be associated with a secondary lymphoma in nearly 50% of cases [51]. The first described dermoscopy in 2020 reported pale orange areas on an erythematous background and fine linear vessels [52]. In 2021 another case report presented dermoscopy in three different types of lesions in 1 patient. Dermoscopic examination of the indurated plaque on the head showed multiple thick, linear irregular vessels with branches, in an unspecific distribution, and white scales in patchy distribution on the brownish-reddish background; the maculopapular lesions showed brownish and orange areas with fine linear vessels on the erythematous background; and the atrophic hyperpigmented lesions showed brownish lines in polygonal/rhomboid arrangement on the orange-red background. The dermoscopic evolution of these lesions was also evaluated. After 10 months of methotrexate therapy, there was no change in the first lesion; in the second lesion, new multiple, orange, well-circumscribed areas located on the background lighter than previously were reported, and in the third lesion, there was partial remission of hyperpigmentations with thinner, lighter polygonal lines. Another dermoscopic examination after a single administration of brentuximab vedotin and oral prednisolone therapy was performed. Authors reported a change of the background color to pale whitish with less marked linear vessels and no scaling in the first lesion, brownish hyperpigmented, focal patches consisting of multiple dots and linear branching vessels in the second lesion; and partial remission of the brownish lines in semicircular distribution, consisting of brown dots located on the pale background [53].
Dermoscopy of poikilodermatous mycosis fungoides
Poikilodermatous mycosis fungoides is a rare variant of mycosis fungoides, which is characterized by predominant poikilodermatous lesions, early age of onset and good prognosis [54]. Dermoscopy of poikilodermatous mycosis fungoides was described in 7 articles, namely 2 original studies [9, 18] and 5 case reports [54–58], including a total number of 19 patients. Dermoscopic findings of poikilodermatous mycosis fungoides were first reported by Xu et al. [57] in 2016 as multiple polygonal structures of lobules of white storiform streaks with dotted and hairpin vessels, surrounded by septa of pigmented dots with red and yellowish smudges. In a study by Elloudi et al. [9], multiple, pigmented polygonal structures and white scales where detected in all patients. In a study by the International Dermoscopy Society published by Errichetti et al. [18], the most commonly observed features included focal white and brown structureless areas (checkerboard pattern), white patchy scales and brown reticular lines. Other reported features included a reticular brown pigment pattern, gray dots, and dotted/glomerular vessels on a pinkish-white background [54, 56, 58]. It is suggested that pigmentary structures may correspond to epidermal basal layer pigmentation, liquefaction and melanophages in the superficial dermis, while white areas and white scaling may correspond to atrophic epidermis/dermal fibrosis and hyperkeratosis [9, 18, 56]. In a case report by Apalla et al. [55] different dermoscopic features of poikilodermatous mycosis fungoides were described, such as striking linear branching vessels in a network pattern with fine sparse white scales on a pink-brown background.
Dermoscopy of purpuric mycosis fungoides
Purpuric mycosis fungoides (PMF) is a very rare variant of mycosis fungoides, which can be clinically indistinguishable from pigmented purpuric dermatosis (PPD). Dermoscopy of PMF was described only in 1 article, including 28 patients with PMF and 13 patients with PPD. The most common dermoscopic features of PMF included dotted vessels (64.3%), spermatozoa-like vessels (50%), fine short linear vessels (35.7%), clustered distribution of the vessels (50%), orange-yellowish background (71.4%) and lack of scales (67.9%). Fine short linear vessels and spermatozoa-like structures were significantly more frequent in patients with PMF, while erythematous globules, dull red background and reticular pigmentation in PPD. Moreover, fine short linear vessels were absent in PPD [7].
Dermoscopy of telangiectatic mycosis fungoides
There is only 1 article from 2017 which reports the telangiectatic variant of mycosis fungoides, clinically mimicking acquired nevoid telangiectasia. On dermoscopic examination, abundant telangiectasia, smaller tortuous vessels and red-brownish patchy areas on the entire lesion were described [4].
Dermoscopy of hypopigmented mycosis fungoides
Hypopigmented mycosis fungoides is a very rare variant of the disease. It predominantly affects pediatric and dark-skinned population [59]. Dermoscopy of the hypopigmented variant was assessed in 1 article on 4 patients with skin of color. The examination revealed patchy, amorphous white-pink areas and loss of the natural pigment network [22].
Dermoscopy of verrucous mycosis fungoides
Verrucous mycosis fungoides is extremely rare. Dermoscopic features of this variant were assessed in 1 article on 2 patients with skin of color. They included multicolored amorphous structures with yellow-gray ridges and comedo-like openings imitating seborrheic keratosis [22].
Dermoscopy of mycosis fungoides developing in the scar
Mycosis fungoides following skin trauma was occasionally reported in the literature [60, 61]. Dermoscopic features were described in 1 patient, in a lesion arising in a keloid scar on the chest after coronary artery bypass graft surgery. They included follicular keratinization and plugging, yellow dots, scales, reticulated and linear blood vessels, multiple discrete ulcers, and elongated white fibrous band [62].
Discussion
This review aimed to increase current understanding of the role of dermoscopy and trichoscopy in mycosis fungoides. The systematic review revealed five most common dermoscopic features with the following sensitivity and specificity: linear vessels (66.1%; 88.2%), white scales (60.1%; 31.0%), orange-yellow focal structureless areas (59.2%; 87.6%), dotted vessels (57.8%; 15.9%) and dull red background color (55.2%; 64.4%). We also found six most specific dermoscopic features in classic mycosis fungoides. These features have the following sensitivity and specificity: linear curved vessels (39.9%; 95.6%), linear vessels with branches (12.3%; 91.3%), linear vessels (66.1%; 88.2%), orange-yellow focal structureless areas (59.2%; 87.6%), purple dots/globules (17.5%; 82.1%) and white focal structureless areas (47.2%; 80.0%).
According to our systematic review, linear vessels are the most common dermoscopic feature of mycosis fungoides with 66.1% sensitivity. They also have a high specificity of 88.2% [9, 13–20]. Importantly, linear vessels in MF tend to have a unique pattern – fine and short [16]. These vessels correspond to dilated vascular structures in the papillary dermis [18].
White scales are quite a common feature, with 60.1% sensitivity, but low specificity of only 31% [9, 13–16, 18–20]. They were reported in all studies in different distributions/shapes (diffuse, central, peripheral, patchy, in the skin furrows, perifollicular, forming geometric shapes) [9, 13–20]. Based on the studies [18, 19], a patchy distribution was most frequently observed. White scales correspond histologically to hyperkeratosis [17]. Despite having quite a high sensitivity, we still believe that white scales are underreported. We find white scales in nearly all our patients with mycosis fungoides. The use of immersion fluid during dermoscopic examination may be the reason for low incidence of this feature.
Orange-yellow focal structureless areas are another feature with high sensitivity and specificity, of 59.2% and 87.6% respectively [9, 13–20]. They correspond to hemosiderin deposits in the dermis (patch/plaque MF) or dense cellular infiltrate (nodular MF) [18].
Dotted vessels with 57.8% sensitivity are the second most frequently observed morphological vascular type after linear vessels. They have a very low specificity of 15.9%, because they are commonly found in many inflammatory diseases [9, 13–20]. Their distribution in mycosis fungoides was mostly described as nonspecific [18, 19, 63].
Dull red background color was assessed only in three studies. The sensitivity and specificity were estimated at 55.2% and 64.4%, respectively. Dull red background color was more common than light red background color [13–15].
Linear curved vessels are the most specific dermoscopic feature of mycosis fungoides with 95.6% specificity. In former studies, metaphoric term spermatozoa-like vessels was commonly used. Spermatozoa-like vessels were first described in patients with mycosis fungoides by Lallas et al. in 2012 [16]. They are a combination of dotted and linear-curved vessels that resemble spermatozoa, therefore we included them in one group with linear curved vessels. Linear curved vessels are highly specific of mycosis fungoides and are rarely found in other conditions. This vascular pattern was not commonly observed, with sensitivity slightly below 40% [9, 13–20]. However, the sensitivity might be underrated due to the usage of different magnifications among studies. They are better visualized at magnifications 20× or higher [17]. Linear curved vessels correspond to dilated vascularity in papillary dermis [18].
Linear vessels with branches were first described in basal cell carcinomas and are characterized as large-diameter vessels that divide into thinner branches [64]. They correspond histologically to dilated, arborizing vessels in the dermis [18]. They have a high calculated specificity (91.3%), but very low sensitivity (12.3%) [13, 17, 18, 20]. They were reported only in 13 patients with the classic variant of mycosis fungoides, including 8 with tumoral and 5 with patch and/or plaque mycosis fungoides [17, 18].
Purple dots/globules have high specificity (82.1%), but low sensitivity (17.5%) [9, 16–20]. They are recognized as the most common feature of pigmented purpuric dermatoses [7, 65, 66]. They correspond to the extravasation of red blood cells and to the increased number of blood vessels, which may be dilated or swollen [67].
The specificity and sensitivity of white focal structureless areas are calculated at 80.0% and 47.2%, respectively [13, 17, 18, 20]. They correspond histologically to dermal fibrosis, which is more prominent in plaque or tumoral MF [18].
We should emphasize that, although white focal structureless areas and linear vessels with branches showed high sensitivity, they were mainly detected in patients with advanced stages of the disease (mostly tumoral). Therefore, their usefulness in diagnosing the early stage of mycosis fungoides is limited.
According to our review, dermoscopic features of erythrodermic mycosis fungoides are similar to classic mycosis fungoides. This is compliant with the fact that these diseases show similar histological findings, therefore final diagnosis is based mainly on the clinical presentation.
Furthermore, in our opinion, trichoscopy is an underrated diagnostic method in mycosis fungoides, especially in folliculotropic and erythrodermic MF. Pili torti (twisted dystrophic hair shafts) were mentioned only in 1 patient with FMF. However, in our experience, they are a very common feature in patients with folliculotropic mycosis fungoides (they are formed probably as a result of folliculotropism with or without mucinosis). Rakowska et al. [68] found them as the most characteristic trichoscopic feature in erythrodermic CTCLs (including all variants of mycosis fungoides and Sézary syndrome, therefore not included in this analysis). Other characteristic trichoscopic features reported for CTCLs altogether include eight-shaped hairs, thick white interfollicular bands, color heterogeneity of the background and perifollicular arrangement of vessels [68]. Although we agree that trichoscopic features of all CTCLs can be similar, it could be beneficial to perform such research in patients with mycosis fungoides selectively.
Based on these results, we decided to highlight features that may be considered as red flags in diagnosing most common subtypes of mycosis fungoides. In classic mycosis fungoides we want to distinguish linear curved vessels (with the highest specificity), along with linear vessels and orange-yellow focal structureless areas (both with high sensitivity and specificity). These features also apply to the diagnosis of erythrodermic mycosis fungoides. In folliculotropic mycosis fungoides, lack of hairs, dilated follicles, follicular plugs as well as pili torti should be considered as red flags.
Our study faced several limitations. Firstly, due to the limited amount of studies, all stages of mycosis fungoides (patch, plaque, tumoral), in various anatomic locations and with different duration time were included in the systematic review. Secondly, inconsistent dermoscopic terminology was used in the studies (metaphoric vs descriptive), therefore we analyzed some features, such as spermatozoa-like structures and linear curved vessels collectively.
In order to fully recognize the role of dermoscopy and trichoscopy in mycosis fungoides approach, more studies with larger cohort groups are required. Furthermore, standardized dermoscopic terms, provided by the International Dermoscopy Society, should be applied to increase comparability between the studies [21]. We also suggest that perhaps assessing the correlation between dermoscopy/trichoscopy and reflectance confocal microscopy (RCM) as well as line-field confocal optical coherence tomography (LC-OCT) could enhance the usefulness of these methods even more.
Finally, we would like to emphasize the importance of this review and systematizing the role of dermoscopy and trichoscopy in mycosis fungoides as well as sharing this knowledge among dermatologists. Unfortunately, as of now, according to Liu et al. [69], a convolutional neural network binary classification model based on an intelligent analysis of dermoscopic images is more successful than dermatologists in differentiating early mycosis fungoides from inflammatory diseases.
Conclusions
Nowadays non-invasive imaging techniques are gaining more popularity in differential diagnosis of many dermatological diseases. Based on the results of this systematic review, dermoscopy and trichoscopy are valuable methods of approaching mycosis fungoides diagnosis, choosing a proper biopsy site, distinguishing its variants, assessing the stage of the disease and treatment efficacy. However, as of now, they cannot replace histopathological examination evaluating cellular atypia and epidermotropism in combination with immunophenotypical and molecular analysis confirming monoclonality of TCR.
Funding
No external funding.
Ethical approval
Not applicable.
Conflict of interest
The authors declare no conflict of interest.
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