Dermatology Online Journal

Sclerosing cellular blue nevus simulating melanoma
Ikbal Esen Aydingoz MD, Emel Dikicioglu-Cetin MD
Dermatology Online Journal 18 (11): 11

Department of Dermatology, Acibadem University, School of Medicine, Istanbul, Turkey

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Abstract

Sclerosing blue nevus is an uncommon variant of common blue nevus and shows an amorphous blue appearance at the edges with a hypopigmented center. Herein we present a 48-year-old female with sclerosing cellular blue nevus with extraordinary clinical and dermoscopic features simulating melanoma. The association of a whitish scarlike area with a pigmented dot pattern prominent throughout the lesion was unusual for a sclerosing cellular blue nevus. Besides pattern asymmetry, polychromasia and linear irregular vessels increased the mimicry. This case illustrates the importance of surgical excision and histopathological examination.

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Introduction

The blue nevus and variants represent a congenital or acquired, dermal collection of pigment producing melanocytes. The prevalence of blue nevus is as high as 3 percent to 5 percent in the Asian population. Sclerosing (desmoplastic) blue nevus represents an uncommon variant of common blue nevus. It is characterized by a paucicellular pigmented dendritic melanocyte and melanophage population embeded in a dense and often hyalinized stroma forming a symmetrical well-circumscribed fibrous nodule [1]. Herein we present a sclerosing cellular blue nevus (SCBN) with extraordinary dermoscopic features.

Case report

Figure 1	Figure 2
Figure 1. Clinical appearance showing dark brown well circumscribed round plaque lesion Figure 2. Dermoscopy showing asymmetric, polychromatic patches in close association with slate gray pigmented dots in addition to the white and structureless paracentral area (Heine x10)

A 48-year-old female presented with a 6-year history of a pigmented lesion on the right temporoparietal scalp that had progressively increased in size during the last 2 years. She was able to follow up the lesion clearly because she had alopecia totalis for 10 years. Cutaneous examination showed a perfectly round, 10 x 12 mm dark brown pigmented, firm plaque. A paracentral hypopigmented and raised area was apparent to the naked eye (Figure 1). Dermoscopy revealed asymmetric, polychromatic patches in close association with slate gray pigmented dots in addition to the white and structureless paracentral area. Hypochromia was noticeable in more than 50 percent of the lesion. Apart from light brown and dark brown, other colors included gray, white, and pink colors. Linear irregular vessels could be visualized at the peripheral margin of the lower right quadrant (Figure 2).

Figure 3
Figure 3. (3a) General histopathological appearance of the lesion (H&E x100), (3b) Section showing an area rich in pigmented melanocytes (H&E x100), (3c) Section showing a hypercellular depigmented area (H&E x200), (3d) Another section displaying a hypocellular depigmented area (H&E x40)

The lesion was excised with a pre-diagnosis of melanoma. However, histopathology revealed a well-demarcated dermal nodule composed of hypocellular fusiform cells and hypercellular depigmented areas with varying consistency and simple lentigo-like findings on its surface. Between these cells, collagen bundles forming band-like structures were present. The lesion showed a compressing growth to the subcutis. Dermal cells stained weakly positive with HMB45 antibody and had a low proliferative rate as shown by Ki-67 antibody immunohistocemically. Masson’s Fontana staining was positive in focally pigmented areas of the lesion. The lesion showed different amounts of pigment, consistent with the presence of varying hypocellular or hypercellular areas (Figures 3a through 3d). A diagnosis of sclerosing cellular blue nevus was made.

Discussion

This is an interesting case of an unusual pigmented lesion with dermoscopic features suggesting melanoma. A typical sclerosing blue nevus is hypopigmented centrally but shows a blue amorphous appearance at the periphery [2]. However, absence of blue color, polychromasia, the presence of a whitish scar-like area together with a pigmented dot pattern, linear irregular vessels, and inner asymmetry seen in our case was in favor of melanoma.

Sclerosing blue nevus is quite rare; in their series of 52 blue nevi, Ferrara et al. reported only three cases and these lesions were white and blue under dermoscopy [3]. Grichnik documented dermoscopic findings of 3 more cases, which showed an amorphous blue appearance with central hypopigmentation [2]. Our case is unusual because of the absence of blue color.

Dermoscopic polychromasia is a term used for the presence of three or more colors in one lesion and is a feature of melanoma and deep penetrating blue nevi [3]. In their study of 95 patients with blue nevi, Di Cesare et al reported 15.8 percent multichromatic pigmentation [4]. In our case the nevus displayed light and dark brown patchy areas at the upper half, but a grayish tone was prominent on the rest of the lesion. In addition white and pink colors generated the polychromasia. These different shades of colors are uncommon for SCBN, but can be explained histopathologically by the pigmented and non-pigmented areas found throughout the lesion containing different amounts of melanin. The gray tones were probably related to the presence of the deep-seated melanin pigment.

In a recent report comparing global and local dermoscopic patterns in blue nevus, melanoma, and basal cell carcinoma, Di Cesare et al. concluded that melanoma were definitely characterized by the association of whitish scar-like areas with dots/globules (p < 0.0001) [4]. Although our patient showed the latter defined features, a diagnosis of SCBN was made. In some variants of blue nevus, hypopigmented areas may also be seen dermoscopically, either because of the loss of melanin or the stromal reaction. Thus, Ferrara et al. have examined 52 cases of blue nevi and its variants and reported such hypopigmented areas in 46.8 percent of the cases [3]. However, a dotted/globular pattern should be very rare; it was not recorded in any of the patients in Ferrara’s study [3]. On the other hand, Di Cesare et al. recorded whitish areas of hypopigmentation and dots/globules in about 20 percent of blue nevi, yet separately [4]. These patterns may be related to the histopathological type of blue nevus. However, it was not mentioned in this study. The pigmented dot pattern seen in our case has not been reported in SCBN before. We consider the hypochromia observed in our patient to relate to the rather deeply seated cellular component, which was composed of pigment poor, spindle-shaped melanocytes and densely collagenized fibrosis. The slate blue dots were regarded as a histopathological correspondence to the melanin present in the dermis or to the clustered melanophages.

The irregular linear vessels showing varying calibers seen at the peripheral margin of the right lower quadrant was noteworthy for both melanoma and other non-melanoma skin cancer. In a dermoscopy study evaluating the vascular structures seen in skin tumors, linear irregular vessels had a positive predictive value of 81.1 percent (p < .001) for melanoma, BCC, and SCC [5]. We think the vascular components seen in our patient may be related to the expanding growth pattern of dermal nodular lesions, which cause compression of the neighboring tissues and lead to congestion and vasodilatation of nearby vessels.

Melanoma was excluded histopathologically, owing to the lack of severe cellular atypia, lymphovascular or adnexial invasion, ulceration, and infiltrative growth pattern at the border. The number of mitoses was 0/mm², the rate of Ki 67 was < 1 percent. Smooth muscle actin was negative, excluding smooth muscle tumors. The absence of nests in the dermoepidermal junction and prominent stromal reaction eliminated deep penetrating blue nevus [1, 6]. The minimal lentiginous proliferation limited to the SCBN found in the patient is unusual, too. The presence of agminate and/or plaque type blue nevus combined with a larger lentigo background has been reported a few times before [7]. However, the significance of this finding within a SCBN remains to be clarified because of the small number of documented cases.

In conclusion, SCBN is a very rare type of blue nevus and owing to the diversity of histopathological constituents and their varying mixture, dermoscopy may show a multicomponent pattern. We believe that this case is a good example of the fact that the dermoscopic data is still limited for the rarely seen pigmented lesions.

References

1. McKee PH, Calonje E, Granter SR. Pathology of the Skin with Clinical Correlations. 3rd edn. China: Elsevier Mosby, 2005.

2. Grichnik JM. Dermoscopy of melanocytic neoplasms: sclerotic blue nevi. Arch Dermatol. 2003 Nov;139(11):1522. [PubMed]

3. Ferrara G, Soyer HP, Malvehy J, Piccolo D, Puig S, Sopena J, Zalaudek I, Argenziano G. The many faces of blue nevus: a clinicopathologic study. J Cutan Pathol. 2007 Jul;34(7):543-51. [PubMed]

4. Di Cesare A, Sera F, Gulia A, Coletti G, Micantonio T, Fargnoli MC, Peris K. The spectrum of dermatoscopic patterns in blue nevi. J Am Acad Dermatol. 2011 Oct 24. [Epub ahead of print] [PubMed]

5. Argenziano G, Zalaudek I, Corona R, Sera F, Cicale L, Petrillo G, Ruocco E, Hofmann-Wellenhof R, Soyer HP. Vascular structures in skin tumors: a dermoscopy study. Arch Dermatol. 2004 Dec;140(12):1485-9. [PubMed]

6. Soyer HP, Argenziano G, Hofmann-Wellenhof R, Johr R. Color atlas of melanocytic lesions of the skin. Heidelberg: Springer-Verlag Berlin, 2007.

7. Marchesi L, Naldi L, Parma A, Locati F, Cainelli T. Agminate blue nevus combined with lentigo. A variant of speckled lentiginous nevus? Am J Dermatopathol 1993;15:162-5. [PubMed]

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