4 курс / Дерматовенерология / Дерматоскопия (3)

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70 Pattern Analysis – Basic Principles

Figure 3.25: Types of vessels.

Vessels may be seen as dots (A), clods (B), or lines (C–H). Lines may be straight (C), looped (D), curved (E), serpentine (F), helical

(G), or coiled (H).

Figure 3.26: Arrangements of vessels.

Vessels may be randomly distributed (A), clustered (B), serpiginous (C) linear (D), centered (E), radial (F), reticular (G), or branched (H).

of vessels, or even absence of a feature. Clues may, but need not necessarily, be present. The more numerous the clues that support a diagnosis (and the fewer that support an alternative diagnosis), the more likely that specific diagnosis is correct. Pattern and color limit the differential diagnoses, but clues confirm a diagnosis or rule it out. Often however, clues are weak, or even contradictory. For these cases, judgement is required in deciding how much weight to assign to each clue, and hence which final diagnosis should be favored. This is discussed in greater detail in chapter 7. As a general principle, more weight should be given to the pattern overall than to any single clue. The most difficult part of dermatoscopy is to correctly assign weight to clues, and particularly to avoid overvaluing an unreliable or misleading clue. This is the role of experience in dermatoscopy.

Pattern of vessels

Blood vessels are visible dermatoscopically due to the hemoglobin they contain. Analysis of vessel pattern(s) often serves as an additional clue to diagnosis. Pat-

terns of vessels are most conspicuous in the absence of pigmentation. In cases of dense melanin pigmentation, vessels are difficult or impossible to visualize.

Patterns formed by vessels are usually much less specific than patterns formed by melanin. As a general principle, whenever pigment is present one should attempt to reach a diagnosis on the basis of these pigmented structures, and relegate blood vessel analysis to the status of a clue to diagnosis. However, when diagnosing non-pigmented lesions, one has to rely on analysis of vessels and keratin structures to reach a diagnosis. Blood vessels are described using the same geometrically defined basic elements used to describe pigmented structures. Like pigmented structures, vessels may appear as dots, clods or lines. Additional line types (looped, curved, serpentine, helical and coiled) are defined for vessels, as these are not seen in pigmented structures. Analogous to patterns formed by pigment, a collection of vessels of the same type gives rise to a pattern of vessels.

Linear vessels are classified based on the number and type of curves (3.25). Those with no curves are termed

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Figure 3.27: Patterns of vessels.

Top left: Monomorphous, small coiled vessels, random arrangement. Top right: Polymorphous, coiled and serpentine vessels, random arrangement. Middle left: Polymorphous; serpentine and curved vessels and vessels as dots, arranged randomly. Middle right: Monomorphous; serpentine vessels, branched. Bottom left: Monomorphous; small coiled vessels, arranged in a serpiginous manner. Bottom right: Polymorphous, vessels as dots and various types of linear vessels, random arrangement.

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72 Pattern Analysis – Basic Principles

“straight”. Those with one curve are termed “looped” when the bend is so sharp that two sections are formed which are sensibly parallel. A vessel with a single obtuse bend is termed “curved”. Vessels with more than one bend are termed “serpentine”. A serpentine vessel is termed “helical” when the curves are focused on a central axis. Vessels are called “coiled” when convoluted compactly.

“Thick” or “thin” and “short” or “long” are additional attributes one may use to describe linear vessels. Logically, the use of these terms is limited to linear vessels. Usually these additional terms contribute nothing to the diagnostic process. However, in exceptional cases these distinctions might provide useful information. Generally, vessels are “thick” only when they are much thicker than normal nail fold capillaries. Vessels are “long” only when they cross a significant part of the lesion and so applies only to straight, serpentine, or helical vessels. Conversely, vessels are “short” only when their length does not greatly exceed their breadth. This applies – if at all – only to straight, curved and serpentine linear vessels.

In addition to the morphology of individual vessels, their arrangement relative to one another and to the lesion as a whole is also important (3.26). In the majority of cases, vessels appear to be distributed randomly, i.e. not arranged in any specific manner throughout the lesion. However, a few important exceptions exist. Vessels as dots or coils may be arranged as lines. When vessels as dots or coils are arranged in straight lines, this arrangement is termed “linear” (it is important not to confuse linear vessels with linear arrangement of vessels). When these vessels are arranged in serpentine lines the pattern is known as “serpiginous”. When vessels are not uniformly distributed but are much more dense at some sites than others, this arrangement is termed “clustered”. Linear vessels of any type at the periphery that are oriented towards but do not cross the center are termed “radial”. The arrangement of linear vessels (most commonly curved, sometimes serpentine or looped) in the center of skin colored or light brown clods is termed “centered”. As for pigmented lesions, we term straight linear vessels that intersect each other nearly at right angles “reticular”. Finally, serpentine vessels may be arranged such that multiple vessels originate from one common vessel; the derivative vessels typically originate from a thicker vessel. This arrangement is termed “branched”. Equipped with these definitions, one may describe the morphology of, and classify, all vascular patterns. Patterns of vessels are described using the same general principles as those used to describe the patterns formed by pigment (3.25, 3.26).

A pattern of vessels is composed of multiple vessels of the same type. When one vessel type predominates over the others, we term the pattern of vessels “monomorphous”. When more than one pattern of vessels is present we use the term “polymorphous”.

Evaluation of the vascular pattern is not always simple. Sometimes one is unable to conclusively assign individual vessels to a specific type. Rather than becoming absorbed in details one should observe the general pattern; the assessment of individual vessels is rarely useful (3.27, 3.28). For instance, in some melanomas one finds – to the extent that pigment allows the vascular pattern to be inspected at all – a mixture of short and straight, short and curved, short and serpentine, and coiled serpentine vessels. The exact classification of individual vessels is not important in this instance; the overall impression is important and that is of polymorphous vessels.

It may be difficult or even impossible to distinguish vessels as dots from vessels as small coils (3.27 top left). At higher magnifications nearly all vessels will have discernable shape; vessels that are dots at magnifications equivalent to the handheld dermatoscope are classified as dots, regardless of their appearance at higher magnifications. Vessels on large, skin colored clods are usually of the linear type; either curved, serpentine or looped (3.29). If each clod contains multiple linear vessels the arrangement is clustered (3.29 top row). If each clod contains a single linear vessel (usually of the curved type) the arrangement is centered (3.29 bottom row).

As regards the occasionally difficult distinction between curved vessels and short serpentine ones, one should remember that curved vessels are usually much thicker than short serpentine ones. Sometimes it is also difficult to decide if there is a specific arrangement of vessels or not. In these doubtful cases it is better to assume that the vessels are arranged randomly. One should also make a distinction between vascular patterns and erythema. Erythema is not a pattern of vessels but a reddening caused by vasodilatation (usually due to inflammation) which, in contrast to a red structureless area, does not cover pigmented structures but gives the background skin a red hue.

Correct technique is critical for dermatoscopic imaging of vessels. Strictly speaking, we do not see the vessels themselves, we see hemoglobin in blood. Too much pressure on the glass plate compresses the vessels and, with blood thus excluded, renders the vessels invisible. For optimum evaluation of vessels one should use a contact medium of higher viscosity, such as ultrasound gel, which is retained between the lesion and the glass plate of the dermatoscope without the use of

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Figure 3.28: Patterns of vessels.

Top left: Monomorphous, large coiled vessels, random arrangement. Top right: Monomorphous, serpentine vessels, branched arrangement. Middle left: Polymorphous; serpentine, curved and coiled vessels; arranged randomly. Middle right: Monomorphous; vessels as dots, random arrangement. Bottom left: Polymorphous; straight and serpentine vessels, radial arrangement. Bottom right: Monomorphous, serpentine vessels, random arrangement.

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Figure 3.29: Vessels on large skin colored clods.

Top: Multiple serpentine vessels on each skin-colored clod is a clustered arrangement. Bottom: Individual curved vessels in the center of each skin-colored clod is a centered arrangement.

pressure. Alternatively, contact with the skin surface (and thus vessel compression) can be avoided entirely by using a polarizing dermatoscope with the contact plate removed. In some cases vessels may be obscured by polarizing-specific white lines and clods, and in these cases they may be visualized more clearly with non-polarizing (contact) dermatoscopy.

Other clues

Vascular patterns are only one of many clues that we use to establish the diagnosis when assessment of pattern and color alone are insufficient. These clues will be addressed in the following chapters describing the principal pigmented lesions. It should be mentioned here that a stepwise description – first of pattern, then color, and finally clues, is the best way of arriving at the diagnosis.

Pattern + Color + Clue = Diagnosis

3.6 Characteristic features of pigmented non melanocytic lesions

3.6.1 Proliferation of vessels Hemangiomas and vascular malformations

Hemangiomas and vascular malformations arguably have the most distinctive dermatoscopic appearance of all lesions. There is one pattern, clods, with color ranging between red and purple, depending on the degree of oxygenation of the blood in the vessels (3.30, 3.31). Black clods are caused by thrombosis of vessels or are indicative of older blood crusts due to exogenous trauma. Other basic elements are completely absent, i.e. there are no lines, pseudopods, circles or dots. In some instances one may find a structureless area adjacent to the clods. Hemangioma should not be diagnosed when any vessels as lines or dots are found within red or purple clods, as this pattern may be seen in amelanotic melanoma.

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Figure 3.30: Hemangioma.

Clinical (left) and dermatoscopic (right) view of a hemangioma. The right figure shows the characteristic dermatoscopic appearance of a hemangioma: one pattern, red or purple clods.

Hemangioma

Pattern	Colors	Clues
Typical:	Typical:	None
Only clods	Red and/or purple
Occasional:	Occasional:
Clods and structureless	Black

1

2

3

4

Figure 3.31: “Senile” angiomas (cherry angiomas).

The overview shows a patient’s back dotted with “senile angiomas” (cherry angiomas) and seborrheic keratoses. The first dermatoscopy image (1) shows a large and relatively heavily pigmented seborrheic keratosis. To its left is a tiny cherry angioma that already demonstrates the characteristic pattern of red clods. Images 2, 3 and 4: on dermatoscopy, angiomas present with only one pattern, namely red clods or, as in example 4, red and purple clods.

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76 Pattern Analysis – Basic Principles

Figure 3.32: Pyogenic granuloma.

Clinical (left) and dermatoscopic (right) view of a pyogenic granuloma. Large pink clods separated by thick skin-colored or white lines and a peripheral white rim are typical of this lesion.

Pyogenic granuloma

Pattern	Colors	Clues
Typical:	Typical:	Typical:
Clods and structureless	Pink, red, white	The clods are separated by thick white or
		skin-colored lines, and the tumor is sur-
		rounded by a white or light-brown margin.
		Occasional:
		Erosions and ulcerations, which are seen as
		orange, dark-red or black clods or struc-
		tureless areas.

Correlation between dermatoscopy and dermatopathology

Red or purple clods correspond to dilated and bloodfilled vessels in the dermis. The color depends on the oxygenation of blood and the location of the proliferation of vessels. Vessels located higher in the dermis are red whereas deeper ones tend to be purple.

Pyogenic granuloma

The pyogenic granuloma is a reactive proliferation of vessels. Its pattern is similar to that of hemangiomas, but the clods are usually pink or bright-red and typically separated from each other by thick, white or skin-colored lines (3.32). Occasionally pyogenic granuloma has a white or light-brown periphery. As pyogenic granuloma is frequently eroded, one may find orange, dark-red or black clods or structureless areas.

Correlation between dermatoscopy and dermatopathology

The pink clods represent dense proliferations of vessels in the dermis, which are separated by septa of connec-

tive tissue (thick, white or skin-colored lines). Pyogenic granuloma is frequently eroded and therefore coated with a crust of blood or serum. These erosions may be seen as orange, red or black clods or structureless areas.

Solitary angiokeratomas

Solitary angiokeratomas reveal a similar pattern of vessels as hemangiomas or senile angiomas. However, in contrast to hemangiomas which are usually marked by bright red clods, solitary angiokeratomas have dark-red, purple or black clods (3.33). Structureless areas are also more common in angiokeratomas than in hemangiomas. Sometimes there is marked hyperkeratosis (3.34). Occasionally it may be difficult to differentiate the purple clods of angiokeratoma from the blue clods pigmented by melanin (like for example in basal cell carcinoma). As a rule of thumb, one should assume that the pigment is hemoglobin if most of the other clods are red, and assume the pigment is melanin when found associated with brown. Of course it is prudent to assume the pigment is melanin in equivocal cases.

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Figure 3.33: Angiokeratoma.

Clinical view of an angiokeratoma: overview (left) and detailed view (middle). On dermatoscopy (right): there is only one pattern, clods, red or black.

Figure 3.34: Angiokeratoma.

Left: Clinical view of an angiokeratoma. Right: Dermatoscopy. There are clods, and their colors are red, purple, and black. Sometimes it may be difficult to differentiate purple clods (pigmented by hemoglobin) from blue clods (pigmented by melanin). If most of the other clods are red, one should assume that the pigment is hemoglobin and not melanin. Note the white structureless zone that corresponds to hyperkeratosis.

3.6.2 Intracorneal hemorrhage

Hemorrhage in the stratum corneum usually occurs on acral skin because the stratum corneum is sufficiently thick at this site. In cases of recent hemorrhage one finds a red or reddish-brown structureless area, or red or reddish-brown clods. However, in case of older hemorrhage the color is black. Typical features of intracorneal hemorrhage are a larger structureless area with a sharply demarcated border (3.35), sometimes surrounded by small satellite clods. At acral sites the pattern may also be of parallel lines following the ridges. In such instances, subcorneal hemorrhage must be differentiated from acral melanoma. At non-acral sites, subcorneal hemorrhage may show the pattern of curved lines.

Correlation between dermatoscopy and dermatopathology

The structureless area, clods and parallel lines represent accumulations of red blood cells in the stratum corneum.

3.6.3 Solar lentigo, seborrheic keratosis and lichen planus-like keratosis

Solar lentigo

The appearance of solar lentigo depends on its location. The most common pattern on the trunk is reticular or curved lines (3.36, 3.37), alone or in combination. Occasionally small brown circles may be superimposed. In facial solar lentigines we can find the structureless pattern, curved lines, a reticular pattern or, albeit rarely, regularly spaced brown circles. Solar lentigines on the forearm and the dorsum of the hand are often structureless and light-brown, sometimes with superimposed brown dots (3.38).

At all sites, the border of solar lentigines is well-de- marcated and scalloped (with multiple concavities). This quality of the border is an important clue to solar lentigo.

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78 Pattern Analysis – Basic Principles

Figure 3.35: Hemorrhage in the stratum corneum.

This hemorrhage on the palm of the hand is seen on dermatoscopy (right) as a reddish-brown or black structureless area. It is sharply delineated from its surroundings.

Intracorneal hemorrhage

Pattern	Colors	Clues
Typical:	Typical:	Typical:
Structureless, clods or parallel lines on the	Red, reddish-brown (recent), black (old)	Sharp contours Small satellite clods
ridges		detached from the main lesion

Figure 3.36: Solar lentigines.

Multiple solar lentigines on the back. On dermatoscopy (bottom row) the reticular pattern is predominant. Reticular lines are thin and light-brown.

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Figure 3.37: Solar lentigines.

Clinical (left) and dermatoscopic (right) view of solar lentigines. Top right: Solar lentigo with curved lines and circles. Middle right: solar lentigo with reticular lines. Bottom left: Solar lentigo with curved lines.