4 курс / Дерматовенерология / Дерматоскопия (3)

Correlation between dermatoscopy and dermatopathology

The brown reticular and curved lines are due to hyperpigmentation of basal keratinocytes when rete ridges are present. The structureless brown pattern corresponds to hyperpigmentation of basal keratinocytes when the epidermis is flat (rete ridges are absent). This is usually the case on chronic sun-damaged skin.

Seborrheic keratosis

No other benign lesion shows the diversity of dermatoscopic appearances seen in seborrheic keratosis (3.39–3.43). Except for the pseudopod pattern, any pattern or color may be found.

Flat seborrheic keratoses (and the flat portions of raised types) on the trunk show similar patterns to solar lentigo, i.e. light-brown reticular or curved lines. With early acanthosis (thickening of the epidermis) and hence thickening of the lesion, thin curved lines (frequently arranged as parallel pairs) and circles become more prominent. With advanced acanthosis, the predominant structures become thick curved lines and clods.

In early acanthosis, brown and orange (or yellow) are the predominant colors seen. Verrucous types when heavily pigmented are marked by thick curved lines in combination with brown and/or orange clods and/or a structureless area in shades of brown, blue or gray. In less heavily pigmented verrucous types the predominant feature is often orange, yellow or skin-colored clods.

White dots or clods are seen in all types of seborrheic keratosis, but become more common in more raised lesions, i.e. with more advanced acanthosis. As with all aggregations of basic elements, white clods or dots must be multiple to form a pattern (though lesser numbers may still constitute a clue).

In addition to white dots or clods, a sharply demarcated border, a scalloped border and looped and/or coiled vessels are important clues to seborrheic keratosis.

Correlation between dermatoscopy and dermatopathology

As in solar lentigo, the brown lines and circles of flat seborrheic keratoses result from hyperpigmentation of basal keratinocytes. Reticular lines may become thick with acanthosis of the epidermis. The hypopigmented areas between lines are dermal papillae and infundibula of the hair follicles. Thick curved lines, clods and circles of raised or verrucous seborrheic keratoses represent invaginations of the epidermis filled with keratin (thick lines and clods) or infundibula (clods and circles) filled with keratin. As white or yellow keratin may be mixed with melanin, the spectrum of colors of lines and clods ranges from yellow (no melanin) to orange (moderate quantity of melanin), brown (large quantity of melanin), and in exceptional cases even black.

White dots or clods correspond histopathologically to cysts filled with keratin. The blue or gray structureless area of some verrucous seborrheic keratoses is due to acanthosis of the epidermis, which causes epidermal melanin to appear blue.

Lichen planus-like keratosis

Lichen planus-like keratosis is actually a solar lentigo (or sometimes a seborrheic keratosis) in regression and may therefore show the same dermatoscopic features as these lesions. Two additional features are clues to lichen planus-like keratosis; erythema (a sign of inflammation) and gray dots and/or clods (3.44).

Once the solar lentigo has disappeared and the inflammation has subsided, complete regression is marked by gray dots and/or clods with no sign of the pre-existing lesion. In this case, of course, other differential diagnoses must be considered, including a fully regressed melanoma. In most cases the distinction is obvious because several lichen planus-like keratoses occur together at typical sites (forearm, dorsum of the hand, face and back). However, a diagnostic biopsy may be necessary in some cases.

Correlation between dermatoscopy and dermatopathology

On histopathology the gray clods or dots represent accumulations of melanophages in the papillary dermis.

3.6.4 Dermatofibroma

The most common patterns of dermatofibroma on dermatoscopy are reticular lines peripherally and structureless white centrally (3.45). Peripheral reticular lines are usually brown and always thin – never thick. Instead of reticular lines there may be dense light-brown circles or, more rarely, regularly arranged radial lines distributed over the entire circumference. Thick white lines in place of the central structureless zone is also a common variant. If the center of the dermatofibroma is brown or red structureless one can also find (polarizing-specific) perpendicular white lines in the center.

There are also other less common patterns of dermatofibroma. For instance, the central white structureless zone may be entirely absent. Instead, one may find a few smaller eccentrically located structureless zones that may be white or skin-colored. Another uncommon dermatofibroma variant has no peripheral lines or circles, consisting entirely of brown, white and skin-colored structureless zones. Usually dermatofibroma have a symmetric combination of patterns and colors but exceptions like the one shown in figure 3.46 exist. The firm consistency on palpation is an additional clinical clue to the diagnosis of dermatofibroma.

Correlation between dermatoscopy and dermatopathology

Thin reticular lines or circles are caused by elongation of rete ridges and melanin hyperpigmentation of basal keratinocytes. White structureless zones, thick white reticular lines and perpendicular white lines are caused by dermal fibrosis. Red or pink pigmentation is caused by inflammation and dilated blood vessels.

3.6.5 Melanotic macules Ink-spot lentigo

The characteristic pattern of ink-spot lentigo is reticular lines (more rarely branched lines) that may be quite thick, but always have a uniform dark-brown or black pigmentation (3.47). A clue is that the reticular lines within the lesion may be interrupted at various sites, and tend to end abruptly at the margin.

Correlation between dermatoscopy and dermatopathology

The reticular pattern of ink-spot lentigo is caused by marked hyperpigmentation (therefore dark-brown or black) of basal keratinocytes at the rete ridges.

Pattern

Typical:

Flat: Reticular or curved lines, circles Moderately raised: Curved lines, clods, circles

Verrucous: Clods, thick curved lines, structureless

Pattern

Typical:

Reticular and structureless

Variants:

Instead of thin brown reticular lines there may be densely arranged light-brown circles; instead of the structureless white center there may be thick, white reticular lines.

Rare:

Completely structureless or radial lines at the periphery (on the entire circumference).

Colors

Typical:

Reticular lines and circles are light-brown, structureless zones are either white or skin-colored.

Clues

Typical pattern:

Reticular (or circles) at the periphery, structureless (or white reticular lines) or white perpendicular lines (only visible with polarized dermatoscopy) in the center.

Genital lentigo, labial lentigo

Regardless of whether labial or genital lentigines occur in isolation or as part of a syndrome, they are characterized by three different patterns: 1. structureless 2. curved parallel lines, and 3. circles. The pigmentation ranges from light-brown to dark-brown (3.48).

Correlation between dermatoscopy and dermatopathology

The structureless pattern correlates with hyperpigmentation of basal keratinocytes in areas where rete ridges are absent or flattened (e.g. on the lip). Patterns of parallel lines and circles are probably due to the special anatomy of the epidermis on the vulva and the penis and of the transition zone between keratinizing epidermis and mucosa.

3.6.6 Pigmented basal cell carcinoma

Pigmented basal cell carcinomas have a diverse, but usually characteristic, dermatoscopic appearance, showing patterns composed only of radial lines, dots, clods and structureless zones (3.49, 3.50). A common pattern and color combination is blue clods that are usually, but not always, of different sizes and shapes. This may occur in isolation or in combination with brown clods, gray, blue and/or brown dots, white structureless zones, and radial lines. All other arrangements of lines (reticular, branched, curved and parallel), as well as pseudopods and circles do not occur in basal cell carcinoma. These structures are all very strong clues against the diagnosis of basal cell carcinoma. The pigmentation of basal cell carcinoma is caused by melanin. The pigmented tumor cell aggregates of basal cell carcinoma appear brown or gray when they are superficial, and blue when they lie deeper. An orange-colored structureless area correlates with an erosion or ulcer coated with serum crusts. Structureless zones are usually central and are skin-colored or white. Clues include peripheral radial lines, seen segmentally (as opposed to occupying the entire circumference). These radial lines may be thin or thick and nearly always have a common base. Radial lines may also converge at a central hyperpigmented dot or clod. These latter structures may be seen centrally as well as peripherally. Both these patterns of radial lines constitute very strong clues to the diagnosis of basal cell carcinoma.

Blue clods constitute a relatively specific feature, not only as a pattern, but also as a clue (when only one or two blue clods are present).

The pattern of vessels in basal cell carcinoma (both pigmented and non-pigmented) is an important clue. The typical vessel pattern of basal cell carcinoma is branched serpentine vessels that originate from a thick

stem (branched pattern of vessels). However, while this pattern is common in nodular basal cell carcinomas it is usually absent in superficial basal cell carcinomas, which are characterized by a polymorphous pattern of vessels consisting of thin, serpentine vessels that are not branched, and occasionally coiled vessels.

Reticular lines and vessels as dots are not seen in basal cell carcinoma and when seen constitute a clue against the diagnosis. Ulceration, which is relatively common in basal cell carcinoma can induce the full variety of polymorphous vessel types including dot vessels, but a pattern of dot vessels is not expected.

Correlation between dermatoscopy and dermatopathology

Blue, gray and brown clods correspond to pigmented tumor cell aggregates. When they are located deep they appear gray or blue. In superficial location they are brown. Radial lines with a common base and radial lines that converge in a central clod arise when several epithelial tumor strands originate from one follicular structure. The histopathological correlate of skin-colored or white structureless zones is the fibrous stroma. In sclerosing basal cell carcinoma, this stroma may constitute most of the lesion. Orange clods or orange structureless areas are usually a sign of erosion coated with serum.

3.6.7 Squamous cell carcinoma

Invasive cutaneous squamous cell carcinoma is rarely pigmented, but pigmentation is not uncommon in both Bowen’s disease and actinic keratosis.

Pigmented actinic keratosis

Pigmented actinic keratoses usually occur on the face. On dermatoscopy they may show a variety of patterns (3.51). Most commonly there are gray and brown dots arranged between the follicular openings. Other common patterns of facial pigmented actinic keratosis are angulated lines, structureless and circles (grey dots arranged around follicular openings). Frequently one can find dermatoscopic criteria of a solar lentigo in addition, for example curved lines or a well demarcated, scalloped border (3.51 bottom row).

The dermatoscopic pattern of gray dots between or around follicular openings can equally be seen in melanoma in situ and solar lentigo in regression (lichen planus-like keratosis). Sometimes these three entities cannot be clearly distinguished from each other on dermatoscopy alone. Clues to pigmented actinic keratosis are scale, white circles and 4 white dots in a square (4-dot clod, 3.51). The latter clue can only be seen with polarized dermatoscopy.