Dermoscopy pathology correlation in melanoma

Giuseppe Argenziano

Abstract

Dermoscopy is a widely used technique whose role in the clinical (and preoperative) diagnosis of melanocytic and non-melanocytic skin lesions has been well established in recent years. The aim of this paper is to clarify the correlations between the "local" dermoscopic findings in melanoma and the underlying histology, in order to help clinicians in routine practice.

Figures (9)

Figure 1. (a) Melanoma showing atypical network, characterized by a combination of thick and dark network and thin and brown network, asymmetrically distributed throughout the lesion, (b) corresponding histopathologically to an irregularly retiform pattern with single pleomorphic melanocytes at the junction (hematoxylin—eosin, original magnification x 400).

Figure 2. (a) This melanoma shows as the predominant feature the blue-white veil, detectable as an irregular structureless area o confluent blue pigmentation with an overlying white “ground-glass” film. (6) At histopathology, it corresponds to a marked and irreg- ular epidermal hyperplasia overlying dermal sheets of pigmented epithelioid melanocytes and melanophages (hematoxylin—eosin original magnification x40).

Figure 3. (a) Dermoscopy shows a combination of irregular dots/globules and peripheral irregular streaks, both typical of mela- noma. (b) Irregular dots/globules correlate histologically with a striking pagetoid configuration (hematoxylin—eosin [HE], original mag- nification x630). (c) On the other hand, streaks are histopathologically represented by peripheral confluent junctional nests of melanocytes (HE, x 100).

Figure 4. (a) In this case, dermoscopy shows irregular blotches, appearing as brown structureless areas asymmetrically distributed within lesion. Other features, such as peppering and atypical vascular structures, are visible. (b) In this case, blotches correspond histologically to melanin at all levels of the epidermis, with irregular junctional nesting of pleomorphic melanocytes (hematoxylin— eosin, original magnification x 250).

Figure 5. (a) In the upper part of the lesion, dermoscopy shows an extensive regression area, namely, a white scar-like depigmen- tation, in which the atypical network characterizing most of the lesion is no longer visible. (b,c) Histopathology shows a flattened dermoepidermal junction with irregular nests of pleomorphic melanocytes overlying a wide area of dermal fibrosis with newly formed vessels, melanophages and perivascular cuffs of lymphocytes (hematoxylin—eosin, original magnifications: [b] x200; [c] x 100).

Figure 6. (a) Hypomelanotic melanoma showing polymorphic vessels, regression and blue-white veil. (6) Atypical vascular pattern histopathologically corresponds to dermal vascular channels, in the present case also with angioma-like features (hematoxylin— eosin, original magnification x 100).

Figure 7. (a) Dermoscopy of typical lentigo maligna showing a predominant gray color distributed in the characteristic granular—an- nular pattern and rhomboidal structures. (b) Histopathology of a lentiginous proliferation of pleomorphic melanocytes with involve- ment of the adnexa and perifollicular pigmentation (hematoxylin—-eosin, original magnification x 200). According to Schiffner et a/., the progression of LM can be evaluated by means of the evolution of some dermoscopic fea- tures. Asymmetrical pigmented follicular openings (also called gray circles) and gray dots in the follicular openings (also called circles in the circle) represent the initial dermoscopic criteria for the early diagnosis of LM. These structures subsequently evolve into a granular—annular pattern, that corresponds to fine gray dots, globules and streaks around the follicles. Finally, melanocytes surround and completely obliterate the follicular openings producing the dermoscopy feature of the rhomboidal structures and the black/gray blotches, respectively.'? The gray color, irrespective of its shape, is the single most impor- tant criterion to differentiate LM from other facial pigmented macules.2° The gray color of structures typically seen in LM, histologically, corresponds to free or intercellular melanin in the upper dermis and/or to intrafollicular melanin (Fig. 7).'%?° Melanoma of the nail matrix is one of the most challenging diagnoses in dermatology because it is prone to be confused with other common benign or malignant ungual and subungual lesions. Dermoscopic patterns of melanoma of the nail appara- tus include: light-to-dark brown background color; brown to black longitudinal lines (irregular in color and thickness); subun- gual hemorrhage (appearing as blood spots or linear microhe- morrhages); and micro-Hutchinson’s sign, defined as a pigmentation of the cuticle invisible to the naked eye.27:°

Figure 8. (a) Dermoscopy of acral melanoma showing a parallel ridge pattern (b,c) histopathologically corresponding to a lentigi- nous and pagetoid pattern made by pleomorphic hyperchromatic melanocytes (hematoxylin—eosin, original magnifications: [b] «200; [c] x630).

Figure 9. (a) Dermoscopy of a clear-cut melanoma showing negative pigment network as the predominant feature, consisting of relatively light areas making up the “cords” of the network, and darker areas filling the holes. (b) It corresponds at histopathology to a relatively regular epidermal hyperplasia with hyperkeratosis/hypergranulosis associated with an irregular junctional nesting of mela- nocytes (hematoxylin-eosin, original magnification x 200).