PMC5315045_01
Clinical (a) image of the right thumbnail of a 50-year-old woman. The pigmented stripe has appeared and progressed over three years. Dermatoscopy (b) displays melanonychia striata with lines parallel varying in width, but not interval or color. [Copyright:  2017 Akay et al.]
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Examination revealed heavily pigmented longitudinal melanonychia (Figure 1a). Taking this variability into account, there were lines parallel varying in width but not varying in interval or color (Figure 1b).
H&E staining (a) of the matrix biopsy specimen from the lesion in Figure 1 displays heavy pigmentation over both the epidermis and dermis which compromised assessment of architecture and cytology. A bleached section (b) revealed an apparent epidermal melanocytic proliferation, but this was initially interpreted as keratinocytes modified by bleaching. Interpretation of sections stained with Melan A (c) and Ki-67 (d) was compromised by heavy melanin pigmentation substantially obscuring DAB chromagen. [Copyright:  2017 Akay et al.]
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Hematoxylin and eosin (H&E) stained material (Figure 2a) revealed heavy melanin staining throughout the epidermis and into the reticular dermis to such a degree that assessment of the architecture and cytology of the lesion were compromised. Bleached sections were examined (Figure 2b), and although these did reveal an apparent melanocytic proliferation in the epidermis it was considered that this could in fact be artifactual due to the bleaching. Sections stained with Melan A (Figure 2c), Ki-67 (Figure 2d) and HMB45 showed staining throughout the epidermis and papillary dermis, but the presence of heavy pigmentation substantially obscured DAB chromogen, making the interpretation difficult and unreliable.