4 курс / Дерматовенерология / Дерматоскопия (3)

2.Combination of reticular lines and/or clods with a skin-colored structureless area

Rare:

1.Only brown dots or small brown clods

2.Brown circles (instead of reticular lines)

3.Brown structureless

Patterns are usually combined symmetrically.

Clues

Typical:

Reticular lines, usually thin, small dots or clods of the same size and nearly the same shape; peripheral dots or clods are larger in the early phase of growth

Occasional:

When visible, usually a monomorphous vascular pattern with vessels as dots, occasional erythema

Rare:

Peripheral radial lines over the entire circumference, black dots on reticular lines

Pattern

Typical:

1.Only clods

2.Reticular lines (or branched lines) and clods; the clods are larger than those in Clark nevus, typically light-brown or skin-colored, and usually in the center of the lesion.

Occasional:

1.Reticular (or branched) lines peripherally and structureless centrally, central hypopigmentation

2.Combination of three patterns: reticular lines, clods and a (usually skin-colored) structureless area

Rare:

Only reticular or branched, or only structureless. All combinations of patterns are usually symmetrical.

104 Pattern Analysis – Basic Principles

or in combination with other patterns, usually reticular or less often structureless. When clods are combined with the reticular pattern, the clods are usually found centrally and not, as in the (growing) Clark nevus, peripherally. Occasionally, congenital nevi with exclusively reticular or curved lines may be found, usually on the extremities. As in Clark nevus, combinations of patterns are usually symmetrical in both “superficial” and “superficial and deep” congenital nevi.

A further clue to “superficial” and “superficial and deep” congenital nevi, especially the more common clod or clod-reticular types is that they are either uniformly brown or hypopigmented in the center. The less common purely reticular types, on the other hand, often have variegate pigmentation. The dermatoscopic presentation of “superficial” and “superficial and deep” congenital nevi is more protean than that of Clark nevi (3.62).

The most specific clue to the diagnosis of congenital nevus is terminal hairs, in greater numbers, or longer and darker, than on surrounding skin. This clue is, however, seen only in a minority of cases. Some “superficial” or “superficial and deep” congenital nevi show dermatoscopic features of seborrheic keratosis, most often white dots or clods, and occasionally orange clods between skin-colored clods. Occasionally there is also peri-infun- dibular hyperpigmentation (brown circles around the infundibula). Other less specific dermatoscopic clues are clods or vessels as dots located in the center of reticular lines, curved lines (primarily in combination with reticular or branched lines), and densely arranged aggregations of small circles.

Occasionally it may be difficult to distinguish between a Clark nevus and a congenital nevus on dermatoscopy, as the reticular pattern may occur alone or in combination

with other patterns in both types of nevus. There also is a morphological zone of overlap with melanoma. Clues to melanoma, especially gray dots and white reticular lines, may be found in some congenital nevi. Occasionally, histopathology is required to make this distinction.

Correlation of dermatoscopy and dermatopathology

The histological correlate of reticular lines was explained in the section on Clark nevi. Brown clods correspond to nests of melanocytes at the dermo-epidermal junction, which are usually larger in congenital nevi than in the Clark nevus. Skin-colored clods arise due to lightly pigmented or non-pigmented nests of melanocytes in the papillary dermis.

The widened dermal papillae filled with melanocytes cause the epidermis to protrude outward, which gives rise in metaphorical terminology of a cobblestone pattern. When the nests of melanocytes are somewhat deeper, i.e. below the dermal papillae, the surface of the is seen as a skin-colored or light-brown structureless area.

Combined congenital nevi

Combined congenital nevi are those showing features of both a “blue nevus” and either a “superficial” or “superficial and deep” congenital nevus (3.63). The dermatoscopy is exactly what one would expect from such a combination. In most cases there is a central blue structureless area (blue nevus), surrounded by brown reticular lines or brown clods (or both). If the blue structureless area is located eccentrically rather than centrally, it is difficult to distinguish a combined nevus from a melanoma. Occasionally, instead of a blue structureless area one sees blue clods, which rarely may be distributed over the entire lesion.

106 Pattern Analysis – Basic Principles

Correlation between dermatoscopy and dermatopathology

Refer to the above sections regarding blue nevi and “superficial” or “superficial and deep” congenital nevi.

Recurrent nevus

On dermatoscopy one typically sees a hypopigmented (lighter than surrounding skin) structureless zone, corresponding to the scar after excision (3.64). The recurrent nevus is within this area. Common patterns seen are peripheral radial lines, pseudopods, and brown clods of different sizes. Radial lines and pseudopods are of course clues to melanoma. In contrast to local recurrence of a melanoma, the recurrent nevus usually does not extend beyond the scar.

Correlation between dermatoscopy and dermatopathology

The radial lines and pseudopods correspond to fascicles of pigmented melanocytes at the dermo-epidermal junction.

Spitz nevus

The “classical” Spitz nevus as described by Sophie Spitz is non-pigmented or only lightly pigmented. On dermatoscopy one most often finds skin-colored or light-brown clods and perpendicular white lines (3.65). Alternatively when the lines seen between the clods are lighter than the normal skin, they are termed white reticular lines. This pattern is also seen in some melanomas and dermatofibromas. In non-pigmented or lightly pigmented Spitz nevi one may find vessels as dots.

The patterns seen in pigmented Spitz nevi are brown clods peripherally; centrally gray or blue-gray clods or structureless (3.66 A, B). This central area is occasionally interspersed with thick, light-gray reticular lines and/ or polarizing-specific white lines.

Spitz nevi are nearly always easily distinguished from Reed nevi. Clinically Spitz nevi are nodular or papular and Reed nevi are flat or only slightly raised. Dermatoscopically, the patterns of established Reed nevi are pseudopods or radial lines. Only in the early stages of growth may one see clods in Reed nevi. (3.66 C, D).

Correlation between dermatoscopy and dermatopathology

Like the previously described nevi, brown clods correspond to pigmented melanocyte nests in the epidermis. White lines are most likely due to zones of fibrosis in the papillary dermis. The gray reticular lines in the center of pigmented Spitz nevi are probably due to

the combination of relatively heavily pigmented nests of melanocytes and acanthosis of the epidermis.

Reed nevus

Serial dermatoscopic photography shows that an early Reed nevus consists solely of dark-brown clods. The characteristic pattern of radial lines or pseudopods at the periphery only develops during subsequent growth (3.67). The radial lines or pseudopods are symmetrically distributed over the entire periphery while there is a black, black-gray or dark-brown structureless area in the center, or occasionally thick, gray reticular lines. Occasionally there are black dots or clods peripherally. Once growth ceases, the radial lines and pseudopods disappear. A Reed nevus is then identical to a darkly pigmented Clark nevus with reticular lines peripherally and a structureless hyperpigmented center, or reticular lines only. One plausible theory suggests this is followed by transepidermal elimination of melanocytes and the disappearance of the nevus. Combinations of patterns in Reed nevus are usually symmetrical. If the pseudopods in a Reed nevus are only seen in some segments of the circumference, it cannot be distinguished from a melanoma dermatoscopically.

Correlation between dermatoscopy and dermatopathology

The pseudopods and radial lines at the periphery are fascicles of pigmented melanocytes at the dermo-epi- dermal junction that have spread centrifugally.

Blue Nevi

Most blue nevi can be diagnosed easily. As we noted in chapter 2, the term “blue nevus” includes various entities which can be distinguished by dermatopathology, but not by dermatoscopy or clinical examination. As this book is primarily focused on dermatoscopy, specific sub-classification will not be performed and the general term “blue nevus” will be used.

The dermatoscopic pattern of all blue nevi is structureless (3.68). Blue nevi usually have only one color, most commonly blue or gray. (When assessing color one exercises latitude: slight variations in shade should not be interpreted as a separate color.) Occasionally one sees variegate blue and gray. Less common again are blue nevi with shades of gray and blue flanked by brown regions. It may then be difficult or even impossible to distinguish between this entity and a combined congenital nevus on dermatoscopy.

Occasionally grey lines or dots may be seen against a blue background. Applying the basic principle that

1.Reticular lines at the periphery and structureless hyperpigmented center

2.Only reticular lines

Combinations of patterns are usually symmetrical, but asymmetrical combinations of patterns do occur.

Clues

Occasional:

Within the structureless area in the center there are thick, gray reticular lines.