4 курс / Дерматовенерология / Дерматоскопия (3)

Hemangioma/vascular malformation

Hemorrhage

Hemangioma/vascular malformation

Seborrheic keratosis

Basal cell carcinoma

Seborrheic keratosis, Sebaceous gland hyperplasia

Congenital nevus (Unna or Miescher nevus) Seborrheic keratosis

Congenital nevus, "superficial" or "superficial and deep" Spitz nevus, Congenital nevus (Unna or Miescher nevus)

Hemangioma, thrombosed, Hemorrhage

Basal cell carcinoma

(5.23), in basal cell carcinoma one usually finds one or two orange clods with traces of red due to red blood cells in the serum crust. A further clue is the pattern of vessels: in basal cell carcinoma serpentine vessels, often branched; in seborrheic keratosis, looped or coiled vessels (only rarely serpentine). White dots or clods may be found in both diagnoses.

Unconscious rules often affect how patterns and morphology are perceived. Understanding these unconscious rules is important in all of dermatoscopy, but it is particularly relevant to the interpretation of white structures. In familiar settings one has no difficulty in establishing which features constitute foreground and which constitute background, but this is not always the case in unfamiliar settings, for example when one is learning dermatoscopy. The unconscious tendency is to interpret what one perceives to be the most prominent features

as the foreground and hence constituting structure. In practice this assumption usually works, but it is incorrect and is a common cause of errors in dermatoscopy.

The correct general principle is that structure is defined by pigment. For example, the spaces between reticular lines are not clods because the (more heavily pigmented) lines represent the structure and the (less pigmented) spaces are merely the background against which the lines are defined. It takes experience and deliberate training of the eye to (when necessary) override unconscious rules and correctly make this distinction between foreground and background.

By definition, a structure is called “white” only when it is clearly lighter than the normal perilesional skin. White structures (lines, circles, dots or clods) are exceptions to the general principle that pigment defines structure. That is, when white structures are seen one should

reverse normal practice and interpret the more heavily pigmented structures as constituting the background against which the hypopigmented white structures are defined.

For the sake of completeness it should be mentioned that, in rare cases, Bowen’s disease (especially when it occurs in conjunction with a seborrheic keratosis) may have only white, yellow and/or orange clods. Invasive squamous cell carcinomas are usually non-pigmented but may have white circles or clods as a clue to the correct diagnosis (13). The diagnosis of non-pigmented lesions is discussed in greater detail in chapter 6.

Red or purple clods are characteristic of hemangioma or vascular malformations (5.24). Thrombosed vessels are seen as black clods. Hemorrhage may be seen as red clods. The differential diagnosis of blue clods is quite different from that of purple or black clods, so this distinction must be made carefully.

Large, polygonal skin-colored clods are usually found in exophytic congenital nevi with a papillomatous surface, such as Unna nevus or Miescher nevus, and also occasionally in verrucous seborrheic keratosis (5.25). In all of these lesions one may also find smaller orange clods interspersed between the skin-colored clods.

When a pigmented lesion consists exclusively of brown clods, various types of melanocytic nevi must be considered in the diagnosis (5.26). Large, polygonal lightbrown clods are primarily signs of an Unna nevus or Miescher nevus, especially when the clinical appearance is papillomatous. Quite often typical curved vessels are found in the center of the clods, but the vascular morphology of these nevi may be highly polymorphous. In general, pigmented lesions should be diagnosed on the basis of their structure and color. A diagnosis made on the basis of the pattern and color should not be discarded because the corresponding pattern of

vessels is absent. The pattern of vessels should, at most, be used to confirm the diagnosis.

Small to medium-sized, round and oval brown clods are characteristic features of small congenital nevi, of both the “superficial” and “superficial and deep” types. Some pigmented Spitz nevi may also have only brown clods, or brown clods peripherally may combine with gray clods or lines centrally (5.27). Central hyperpigmentation is also common in pigmented Spitz nevi, and peripheral clods are usually smaller than those in the

center. However, these clues are not sufficiently specific to always distinguish Spitz nevi from small congenital nevi. Blue clods are characteristic of pigmented basal cell carcinoma (5.28). While melanoma and combined congenital nevus may also show a pattern of blue clods, they nearly always also have clods of other colors, or another pattern in addition to blue clods. Therefore, when confronted with only blue clods one should first look for clues to support or refute a diagnosis of basal cell carcinoma.

More than one color

When one finds clods of different colors it is helpful to distinguish between the colors of melanin and the colors of other pigments (5.29). Clods whose pigmentation is due to melanin are brown, blue or gray. Although melanin may also appear black on dermatoscopy, a pattern of black clods is nearly always a sign of the blood pigment hemoglobin. Accumulations of melanin appear black in the stratum corneum but usually appear as dots rather than as clods. When one finds black melanin clods, there are almost never enough to form a pattern. To differentiate between melanin and hemoglobin one may also consider the other colors present in the lesion. If black clods appear together with red or purple clods it is almost always hemoglobin. If black

clods appear together with brown clods it is likely that the pigmentation is due to melanin.

White, yellow or orange clods signify keratin with (orange) or without (white or yellow) inclusions of melanin. However, orange clods may also result from ulceration (serum crust). White or yellow clods are mainly found in seborrheic keratoses and less often in Unna nevi (5.30). Orange clods in large numbers also indicate a seborrheic keratosis or less often an Unna nevus. In addition, just a few orange clods can be produced by ulceration in a basal cell carcinoma. When any combination of red, purple or black clods is seen, the differential diagnoses are the same as for a pattern of clods with only one of these colors; hemangioma, vascular malformation or hemorrhage.

As emphasized in chapter 3, hemangioma must not be diagnosed if vessels are seen as dots or lines. Ignoring discrete vessels in this situation could lead to the grave error of misdiagnosing a non-pigmented nodular melanoma.

When the pattern is clods and the colors of melanin (brown, blue or gray) predominate, the possible differential diagnoses includes congenital nevi (all types including Unna nevi), pigmented Spitz nevi, basal cell carcinoma, and melanoma (5.31). The distinction between nevi and these two malignant diagnoses can usually be made on the basis of the presence or absence of additional clues. Rarely a seborrheic keratosis, especially the so-called “clonal” type can present with a pattern of brown and gray clods (5.32).

5.1.5 Dots

The pattern of dots usually occurs in combination with other patterns. When a pattern of dots does occur in isolation, diagnosis proceeds as usual, by assessing color. In practice, only gray or brown dots are found in lesions without another pattern. When only red dots are found, i.e. vessels as dots, the lesion is assessed as a non-pigmented lesion (chapter 6). When gray dots are predominant, the differential diagnosis includes lichen planus-like keratosis (solar lentigo in regression), pigmented actinic keratosis or pigmented Bowen’s disease, and melanoma (5.33). Differentiating between these diagnoses on the basis of additional clues may be quite challenging, and is sometimes impossible (5.34). In cases of lichen planus-like keratosis one

Gray dots

present

Dots

Only brown

dots present

Lichen planus-like keratosis (solar lentigo or seborrheic keratosis in regression) Pigmented actinic keratosis

Pigmented Bowen’s disease Melanoma with regression

Clark nevus

Solar lentigo

Pigmented Bowen’s disease

Pigmented purpuric dermatosis

may find residual features of the original solar lentigo or seborrheic keratosis e.g. curved lines or the typical sharply defined and scalloped border. Lichen planus-like keratosis occurs usually – but not exclusively – on chronic UV-exposed sites such as the face or the dorsum of the hand, surrounded by other solar lentigines and other signs of UV-related aging of the skin. Quite often one may find several lesions simultaneously.

Pigmented actinic keratoses occur predominantly on the face whereas pigmented Bowen’s disease preferentially occurs on the trunk and the extremities. Pigmented Bowen’s disease is notorious for mimicking other lesions, but usually the clues of coiled vessels and dots arranged as lines lead to the correct diagnosis (14). Finally, in situ melanomas may also have gray dots, usually mixed with

brown dots. Distribution may be random, or (mainly on the face) dots may be arranged as circles or as angulated lines around the openings of the infundibula (15). On the trunk or the extremities, the gray and brown dots of an in situ melanoma may also form angulated lines (polygons). These angulated lines on non-facial skin are much larger than structures formed around infundibular openings (7).

Finally it should be mentioned that some inflammatory skin diseases are associated with melanophages in the dermis and so may also have gray dots. In most such cases, one must rely on the clinical signs to reach the correct diagnosis.

The exclusive presence of brown dots usually indicates a Clark nevus. Rarely a solar lentigo or pigmented

Bowen’s disease may also have only brown dots. The combination of brown and red dots may also occur in inflammatory skin diseases associated with extravasation of red blood cells, such as various forms of pigmented purpuric dermatosis. As in other inflammatory skin diseases, clinical signs rather than dermatoscopy lead to the correct diagnosis.

5.1.6 Structureless

When no basic elements are seen, or there are too few to constitute a pattern, or the visible structures cannot be reliably assigned to just one of the five basic elements, this is termed a structureless pattern. However, “structureless” does not mean “featureless” – whether due to different shades of color within the lesion or a type of “granularity”. One should therefore avoid the term “homogeneous”. The structureless pattern is the least specific pattern, thus giving rise to a long list of differential diagnoses. In the absence of structure, color may be the only clue. Even clues are often absent because most clues are based on some kind of “structure”. In summary, lesions that only have a structureless pattern are difficult to diagnose using dermatoscopy and therefore often require histopathology.

One color predominates over all others

The colors black, blue, brown and red are of practical relevance (5.35). Black and structureless usually indicates the presence of hemoglobin (not melanin) and its degradation products. Hemorrhagic crusts, hemorrhages in the epidermis in general, and thrombosed vessels all appear black and structureless. In exceptional cases, melanin in the stratum corneum can entirely cover all other structures and colors. The differential diagnosis

then includes heavily pigmented melanocytic lesions like Reed nevus, Clark nevus or melanoma.

A blue structureless pattern is quite specific for blue nevi of all types. One should keep in mind the fact that a blue nevus may – in addition to blue structureless zones – have gray or even brown areas which make the nevus appear variegate. Within blue or dark-gray structureless zones one may also find light-gray areas that could be interpreted as structures – usually lines or clods. In accordance with general principle that structures are defined by pigment, these light-gray lines or clods should be ignored, as they have less (not more) pigment than the surrounding area and so should not be considered to be structures.

In exceptional cases, melanomas and metastases of melanomas may be blue and structureless. However, even in these exceptional cases one finds additional clues to the correct diagnosis. These clues include black dots and gray lines, which should not be present in a blue nevus. Unlike blue nevus, there will be a history of progressive growth. Metastases of melanoma can usually be diagnosed on the basis of their clinical features in combination with the past history of melanoma. Apocrine hidrocystomas and exogenous pigmentation (for example tattoos) can be structureless blue. Structureless blue pigmented basal cell carcinomas have also been reported, but these are excessively rare. A history of progressive growth or the presence of clues to basal cell carcinoma may alert the clinician to this possibility. The brown and structureless pattern indicates solar lentigo, flat seborrheic keratosis, pigmented Bowen’s disease, or melanocytic nevus, usually of the “superficial” or “superficial and deep” congenital type. A red structureless lesion is created by a recent hemorrhage