The diagnostic value and histologic correlate of distinct patterns of shiny white streaks for the diagnosis of melanoma: A retrospective, case-control study

Abstract

Background:

Shiny white streaks (SWSs) are best visualized with polarized dermoscopy and correlate with dermal fibroplasia histopathologically. SWSs have been described at higher frequencies in melanomas than in benign nevi.

Objective:

We assessed the diagnostic value of different patterns of SWSs and their histologic correlate in melanocytic lesions.

Methods:

Polarized dermoscopic images of 1507 histopathologically diagnosed melanocytic neoplasms were analyzed for presence and pattern of SWSs. Histology was also reviewed for correlation.

Results:

Among 1507 melanocytic neoplasms, SWSs were observed in 31 of 144 melanomas (22%) and 22 of 1363 benign neoplasms (1.6%) (P < .001). The sensitivity and specificity of SWSs for melanoma were 22% and 98%, respectively. Diffuse SWSs exhibited the greatest diagnostic value for melanoma, with sensitivity of 11.8% and specificity of 99.5%. Focal central and peripheral SWSs were comparable in diagnostic significance. The presence of SWSs was highly uncommon in dysplastic nevi, whereas in certain benign subgroups of nevi such as Spitz nevi and atypical genital special site nevi, SWSs were not uncommon. Diffuse SWSs correlated with greater breadth of deep fibroplasia than focal SWSs (P = .009), and SWSs correlated with greater Breslow depth among melanomas (P = .007).

Limitations:

This study was retrospective.

Conclusion:

Polarized dermoscopy is a valuable diagnostic tool in the identification of SWSs, a feature that is highly specific for melanoma.

Dermoscopy relies on either fluid immersion (contact, incident, and nonpolarized light dermoscopy) or cross polarization (noncontact, polarized light dermoscopy) to reduce light scatter at the air-skin interface. These different methods may have an impact on the colors and structures that are displayed. Polarized dermoscopy allows for better visualization of deep structures and shows structures not otherwise seen with nonpolarized dermoscopy, including 4-dot clods (also known as rosettes) and shiny, bright, linear and white lines, also known as shiny white streaks (SWSs).^1,2 The recent consensus on dermoscopic terminology has replaced the terms chrysalis and crystalline structures with SWSs.³ The presence of SWSs has been histologically correlated with dermal fibrosis with horizontal bands of collagen extending into the superficial reticular dermis.^4,5

The presence of SWSs has been reported in both benign and malignant lesions, including melanoma, Spitz nevus, dysplastic nevus, intradermal nevus, basal cell carcinoma, derma tofibroma, scar tissue, and benign lichenoid keratosis.^6–10 Previous studies have suggested that the presence of SWSs is of importance in the diagnosis of melanoma, with a higher prevalence in melanomas (range, 23.4%−32.8%) than in melanocytic nevi (range, 0.07%−1.6%).^7–9,11 In this study, we aimed to assess the frequency and specificity of SWSs for melanoma among 1507 consecutive melanocytic neoplasms selected for biopsy in which a dermoscopic image was taken in a clinic designated for the care of patients with an elevated risk for melanoma. Further, we assessed the specificity of different patterns of SWSs for melanoma and the specificity of SWSs for melanoma when combined with other melanoma-specific features. Finally, we assessed the histology of all lesions with SWSs and all melanomas in the study to better characterize the histologic changes correlating with SWSs.

METHODS

After obtaining approval from the Northwestern University Institutional Review Board, we performed a retrospective search of our database for dermoscopic images with histologically confirmed diagnoses taken between October 2014 and April 2017. Images were obtained with the DermLite Foto II Pro (3GEN LLC, Dana Point, CA) attached to a Nikon D810 (Nikon Inc, Japan) or DermLite Foto attached to a Canon Powershot G12 (Canon Inc, Japan). Only lesions with a histopathologic diagnosis of a melanocytic neoplasm were included in the study. Malignant neoplasms included all melanomas except those on acral or mucosal sites. Benign neoplasms included lentigos, common nevi, dysplastic nevi, and Spitz nevi/tumors. Dermoscopic images were analyzed for the presence of SWSs by 2 authors (A.E.V and P.G.), with final determinations made by P.G. The dermoscopic images were evaluated to determine the extent of SWSs (focal or diffuse). Focal was defined as the presence of SWSs in a limited area of the lesion (approximately ≤30% of the entire lesion), and diffuse was defined as SWSs spread widely through the lesion (>30% of the entire lesion). We also assessed the localization of the SWSs (central or peripheral). Additionally, we assessed each case for the presence or absence of 9 other well-known melanoma-specific dermoscopic patterns: negative pigment network, atypical pigment network, radial streaming and pseudopods/streaks, atypical dots and globules, irregular blotches, blue-white structures over raised areas, regression structures, atypical vascular structures, and peripheral brown structureless areas.¹²

For all melanomas and all lesions with SWSs, hematoxylin-eosin–stained sections were reviewed by K.W. and P.G., who were blinded to the diagnosis and dermoscopic image. The following parameters were assessed: (1) presence of dermal fibroplasia, (2) whether this fibroplasia was superficial or superficial and deep, and (3) breadth of the superficial and deep fibroplasia, as measured in millimeters by using an ocular micrometer in the microscope. Superficial fibroplasia was defined as fibroplasia limited to the papillary dermis. Deep fibroplasia was defined as fibroplasia expanding the papillary dermis or extending into the reticular dermis.

Statistical analysis was performed with IBM SPSS software (version 23, IBM Corp, Armonk, NY). The association between categorical variables was evaluated with Fisher’s exact test. To evaluate associations of continuous variables, such as breadth of fibroplasia, the Mann-Whitney U test was used. A 2-tailed P value less than .05 constituted statistical significance. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated using 2 × 2 contingency tables.

RESULTS

A total of 1507 dermoscopic images of melanocytic neoplasms were analyzed for the presence of SWSs (Table I). The lesions consisted of 144 melanomas and 1363 benign melanocytic neoplasms. The clinical characteristics of all melanocytic neoplasms, dysplastic nevi, and melanomas are summarized in Table II. Of these cases, 53 neoplasms (3.5%) were identified with SWSs: 31 melanomas, 14 dysplastic nevi, 2 atypical genital special site nevi, 5 benign spitzoid neoplasms (Spitz nevi or Spitz tumors), and 1 intradermal nevus. Three lesions were located on the head and neck, 10 on the upper extremities, 24 on the trunk, 14 on the lower extremities, and 2 on the genitalia. All 3 lesions on the head and neck were melanomas, and both lesions involving the genitalia were atypical nevi of special site. The dysplastic and atypical genital site nevi included 8 cases graded as severe, 7 as moderate, and 1 as mild. The lesions with SWSs came from 51 patients (26 men and 27 women) ages 13 to 88.

Table I.

Frequency of SWSs by diagnosis among melanocytic neoplasms

Diagnosis	No. of cases	SWS (% of diagnosis)		p value
		Yes	No
Melanoma	144	31 (22%)	113 (78%)
Benign	1363	22 (1.6%)	1341 (98.4%)	<.001
Dysplastic nevus	1124	14 (1.2%)	1110 (98.8%)	<.001
Common nevi	178	1 (0.6%)	177 (99.4%)	<.001
Lentigo	30	0	30 (100%)	.003
Spitz nevus/tumor	21	5 (24%)	16 (76%)	.782
Genital site	10	2 (20%)	8 (80%)	1.000

SWS, Shiny white streak.

Table II.

Clinical characteristics

Clinical characteristic	All melanocytic neoplasms	Dysplasticnevi	Melanoma
Median age, y	38	37	51
Sex
Female	934 (62%)	696 (61.9%)	77 (53.5%)
Male	573 (38%)	428 (38.1%)	67 (46.5%)
Location
Trunk	967 (64.2%)	812 (72.2%)	66 (45.8%)
Extremities	366 (24.3%)	228 (20.3%)	47 (32.6%)
Head/neck	93 (6.2%)	18 (1.6%)	31 (21.5%)
Breast	68 (4.5%)	66 (5.9%)	—
Genitals	11 (0.7%)	—	—
Degree of atypia	—		—
Mild		509 (45.3%)
Moderate		475 (42.3%)
Severe		140 (12.5%)

The presence of SWSs was seen in 31 melanomas (22%) and in 22 benign neoplasms (1.6%) (P < .001). The overall sensitivity of SWSs for melanoma was 22% (31 of 144) and the specificity was 98% (1341 of 1363). The PPV and NPV were 58% and 92%, respectively.

A diffuse distribution of SWSs was seen in 17 melanomas (12%) and 7 benign melanocytic neoplasms (0.51%) (P < .001). The melanomas included 9 MIS, 6 T1 melanomas, and 2 T2 melanomas. In the 7 benign lesions, diffuse SWSs were seen in 3 of 1124 dysplastic nevi (0.3%), 2 of 21 Spitz nevi/tumors (9.5%), and 2 of 10 atypical genital special site nevi (20%). The sensitivity of diffuse SWSs for melanoma was 11.8%, and the specificity was 99.5%. The PPV was 70.8%, and the NPV was 91.4%.

Focal SWSs were seen in 14 of 144 melanomas (9.7%) and 15 of 1363 benign melanocytic neoplasms (1.1%) (P < .001). The melanomas included 4 MIS, 9 T1 melanomas, and 1 T2 melanoma. The benign melanocytic neoplasms included 11 of 1124 dysplastic nevi (1.0%), 3 of 21 spitzoid neoplasms (14%), and 1 intradermal nevus. The respective sensitivity and specificity of focal SWSs for melanoma were 9.7% and 98.9%. The PPV and NPV were 48.3% and 91.2%, respectively. Cases with focal SWSs were further separated into a central or peripheral distribution. Focal central SWSs appeared in 5 melanomas (3.5%) and 10 benign melanocytic neoplasms (0.7%) (P < .001), leading to a sensitivity of 3.5%, specificity of 99.3%, PPV of 33.3%, and NPV of 90.7%. Nine melanomas (6.3%) and 5 benign melanocytic neoplasms (0.4%) displayed focal peripheral SWSs (P < .001), resulting in a sensitivity for melanoma of 6.25%, specificity of 99.6%, PPV of 64.3%, and NPV of 91.0%.

All but 1 of the 53 cases with SWSs had 2 or more additional melanoma-specific dermoscopic features; the 1 case, a Spitz nevus, had 1 additional melanoma-specific feature. Of the 52 cases, 31 were melanomas and 21 were benign melanocytic neoplasms. Diffuse SWSs was observed with 2 or more melanoma-specific features in 17 melanomas (11.8%) and only 6 benign melanocytic neoplasms (0.4%). Fourteen melanomas (9.7%) and 15 benign melanocytic neoplasms (1.1%) showed focal SWSs with 2 or more additional melanoma-specific dermoscopic features. These data are summarized in Table III.

Table III.

Sensitivity and specificity of patterns of SWSs with 2 or more additional melanoma-specific features for melanoma among all 1507 melanocytic neoplasms

Pattern of SWSs	Melanoma, n	Benign neoplasms, n	Sensitivity, %	Specificity, %	PPV, %	NPV, %
Any	31	21	21.5	98.5	59.6	92.2
Diffuse	17	6	11.8	99.5	70.8	91.4
Focal	14	15	9.7	98.9	48.3	91.2
Focal central	5	10	3.5	99.3	33.3	90.7
Focal peripheral	9	5	6.3	99.6	64.3	91.0

NPV, Negative predictive value; PPV, positive predictive value; SWS, shiny white streak.

Superficial fibroplasia measured an average of 3.87 mm in cases with diffuse SWSs and an average of 3.88 mm in cases with focal SWSs (P = .740). In contrast, the breadth of deep fibroplasia measured an average of 2.75 mm in cases with diffuse SWSs but measured only 1.52 mm on average in cases with focal SWSs (P = .009).

Specifically among melanomas, the breadth of deep fibroplasia measured an average of 2.61 mm in lesions with SWSs present and 0.92 mm in lesions without SWSs (P < .001). The average breadth of deep fibroplasia was measured as 2.98 mm in diffuse patterns and 2.16 mm in focal patterns (P = .253). Melanomas with SWSs had a mean Breslow depth of 0.34 mm versus 0.15 mm for melanomas without SWSs (P = .007). SWSs were observed more often in invasive melanomas (37%) than in MIS (18%), but the difference did not reach statistical significance (P = .105).

DISCUSSION

The visualization of SWSs as thin, shiny, linear, white structures is dependent on the use of polarized dermoscopy. The visualization of SWSs is related to the birefringent properties of thickened collagen in the superficial reticular dermis causing rapid randomization of polarized light.^4–6,8,13 Thickening of collagen and stromal fibroplasia expanding the papillary dermis or extending into the reticular dermis is a common finding in melanomas as a result of the host response to the neoplastic cells (Figs 1 and 2). This is particularly common in invasive melanomas but can occur less frequently in MIS. In our study we found a statistically significant correlation between the breadth of deep stromal fibroplasia and the presence of SWSs. Melanomas with SWSs had broader deep fibroplasia compared with melanomas without SWSs (P < .001). Furthermore, the presence of SWSs was more frequent in invasive melanomas (37%) than in MIS (18%), and there was a statistically significant correlation between breadth of deep fibroplasia and Breslow depth (P = .007). Not surprisingly, a greater degree of invasion will invoke a more notable deep stromal fibrotic response giving the clinical appearance of SWSs by polarized dermoscopy.

Fig 1.

A, Superficial spreading melanoma from the right thigh of a 48-year-old man with a Breslow depth of 1.1 mm. The lesion has diffuse shiny white streaks throughout, a blue-gray veil, and peripheral brown structureless areas. B, At ×100 magnification one can appreciate confluent junctional nests of highly atypical melanocytes effacing the epidermis and extending into the dermis. There is ribbon-like thickening of collagen strands in the reticular dermis directly below the tumor. At ×200 magnification (inset) one can see the contrast of the thick ribbon-like collagen in the superficial reticular dermis compared with the surrounding collagen.

Fig 2.

A, Superficial spreading melanoma from the left upper back of a 30-year-old woman with a Breslow depth of 0.34 mm. This lesion shows asymmetric streaks all along the superior border, atypical dots and globules, and an area with milky red and focal shiny white streaks in the inferior portion. B, At ×100 magnification, highly atypical melanocytes arranged in single pagetoid cells and nests are seen in the epidermis. The papillary dermis is focally expanded by markedly thickened collagen that also extends into the superficial reticular dermis.

The presence of SWSs on dermoscopy has been reported as a strong clue to malignancy in melanocytic neoplasms. In our study, 22% of melanomas showed the presence of either diffuse or focal SWSs, whereas only 1.6% of benign melanocytic neoplasms showed SWSs. This indicates that the presence of SWSs in a melanocytic neoplasm is a valuable clue favoring malignancy, even in the setting of a high-risk melanoma clinic, where many patients have dysplastic nevus syndrome and highly irregular nevi. Our findings are consistent with those previously published, which have reported the presence of SWSs between 23.4% to 32.8% in melanomas and 0.07% to 1.6% in nevi.^5,7,8,11 Our cases were specifically nevi from patients in a high-risk melanoma clinic who were selected for biopsy with some concern for the possibility of melanoma. Our findings further support the premise that SWSs in melanocytic neoplasms from high-risk patients favors a diagnosis of melanoma.

Overall, the sensitivity of SWSs for melanoma was 22% (31 of 144) and the specificity was 98% (1341 of 1363). The PPV and NPV were 58% and 92%, respectively. The diffuse pattern of SWSs was most sensitive and specific for melanoma, with a sensitivity of 12% versus 6% for peripheral focal and 4% for focal central SWSs. Although the specificity of all 3 patterns of SWSs including diffuse, focal central, and focal peripheral were fairly similar, varying from 98% to 99% in our study, because diffuse SWSs were particularly uncommon in the nevus groups, the PPV of the diffuse pattern was the highest, at 71% versus 63% for the focal peripheral and 33% for the focal central patterns Hence, the diffuse pattern of SWSs was most predictive of a diagnosis of melanoma. However, the presence of SWSs in a focal peripheral or focal central distribution still had a relatively high specificity for melanoma. This emphasizes the importance of familiarity with and utilization of polarized light as a routine part of dermoscopic evaluation because SWSs are not well visualized without polarized dermoscopy.

There were some particular categories of benign melanocytic neoplasms in which SWSs were less specific for melanoma. Of the Spitz nevi/tumors in our study, 24% (5 of 21) exhibited SWSs of any type. Previous study subgroups in the literature of fewer than 10 benign Spitz lesions have reported between a 22% to 100% prevalence of SWSs.^4,5,7,8 In the largest study of 165 Spitz nevi/tumors, Moscarella et al described 16.4% with SWSs.¹⁴ Among our cases, 2 of 10 vulvar nevi presented with SWSs, both in a diffuse pattern. Other studies have shown that as in other cutaneous sites, melanocytic lesions in genital sites with melanoma-specific dermoscopic features, including blue-white veil, atypical network, atypical vessels, multiple colors, and structureless zones, should be considered highly suggestive of melanoma.^15–20 The relatively high prevalence of SWSs among our genital cases suggests that this feature may not be as highly predictive of melanoma in this special site. Deep dermal sclerotic changes are not an uncommon finding in atypical nevi of genital skin; hence, our findings are not entirely surprising, although they have not been previously reported. Given these findings, Spitz nevi and atypical genital special site nevi are 2 benign subclasses of melanocytic neoplasm that may show SWSs at significantly higher frequencies than other classes of nevi and at frequencies comparable to that seen in melanoma. This highlights the importance of integrating the clinical scenario into the diagnostic impression. For example, a stable melanocytic neoplasm with SWSs in the vulvar region of a young woman without other dermoscopic features specific for melanoma may be a lesion suitable for clinical and dermoscopic monitoring, thus avoiding surgery in a delicate area (Fig 3). Likewise, a relatively symmetric lesion suspected to be a Spitz nevus or nevus of Reed in younger patients with SWSs may still be a candidate for clinical monitoring depending on other clinical parameters (Fig 4). The presence of SWSs organized as orthogonal lines is 1 pattern of SWSs that can be seen in spitzoid neoplasms.^14,21,22

Fig 3.

A, Atypical compound nevus of vulvar skin from a 42-year-old woman. The dermoscopic images show peripheral areas with reticulation and a central structureless area with vascular blush with diffuse shiny white streaks throughout. B, At ×20 magnification one can see a broad compound melanocytic neoplasm with an extensive junctional component that broadly involves both lateral margins of the figure. Inset 1 at ×100 magnification (left) shows an area of dermal melanocytes with noticeable surrounding host stromal fibroplasia, which is the histologic correlate of shiny white streaks seen on dermoscopy. Inset 2 (right) shows ×200 magnification of the junctional component, which had prominent lentiginous growth of melanocytes as well as areas with suprabasal movement.

Fig 4.

A, A typical Spitz tumor from the left forearm of 13-year-old boy. The lesion has an inverse pigment network, milky red areas, and shiny white streaks throughout the center of the lesion. B, At ×100 and ×200 magnification (inset) there is a compound spitzoid melanocytic neoplasm with overlying epidermal hyperplasia. There are thick ribbon-like bands of collagen entrapping dermal nests in the papillary and reticular dermis.

All our melanoma cases with SWSs had 2 or more additional melanoma-specific dermoscopic features. When combined with any distribution of SWSs in a melanocytic lesion, the specificity for melanoma exceeded 99%. Table III shows the specificity of each pattern (diffuse, focal peripheral, and focal central) of SWSs for melanoma alone or combined with other dermoscopic features specific for melanoma. In our series, we did find some unusual nevi with multiple additional melanoma-specific dermoscopic patterns. We believe that this is related to the high-risk population involved in the study and their tendency to make unusual nevi. Overall, these nevi with SWSs and multiple additional atypical dermoscopic features constituted only a small proportion (1.6%) of the total nevi on which a biopsy was performed.

In conclusion, our study suggests that the presence of SWSs on polarized dermoscopy, a finding that histologically correlates with broad deep dermal fibroplasia, is an important clue to malignancy in melanocytic neoplasms. Cases with diffuse SWSs had a significantly greater degree of deep fibroplasia than did those cases with only focal SWSs. Melanomas with SWSs had a greater degree of deep fibroplasia than did those without SWSs. The specificity of SWSs for melanoma in a high-risk population of patients who often have many irregular dysplastic nevi was 98%, and the PPV was 58%. The presence of 2 or more additional melanoma-specific features brought the specificity to higher than 99%. In general, the presence of diffuse SWSs was most predictive of melanoma, and outside of the setting of genital nevi or Spitz neoplasms, lesions with this finding should be subjected to biopsy to exclude melanoma.

CAPSULE SUMMARY.

• Shiny white streaks (SWSs) are visible on polarized dermoscopy in melanoma and Spitz nevi but are infrequent in dysplastic nevi. They correlate histopathologically with dermal fibrosis.

• When observed in melanocytic lesions, SWSs are highly specific and predictive for melanoma.

• Polarized dermoscopy to identify SWSs is integral to the evaluation of melanocytic lesions.

Abbreviations used:

MIS

melanoma in situ

NPV

negative predictive value

PPV

positive predictive value

SWS

shiny white streak