4 курс / Дерматовенерология / Дерматоскопия (3)

the ridges is in the colors of melanin, the diagnosis of melanoma must be considered, even in the absence of other clues to melanoma. Hemorrhage or exogenous pigmentation are the likely diagnoses when colors other than those of melanin are seen.

When the pattern is the furrowor crossing-pattern, a distinction is made between symmetrical and asymmetrical combinations of patterns. Symmetrical combinations are found in classical acral nevi and all other nevi, such as Reed nevi or “superficial” and “superficial and deep” congenital nevi (5.52 left). Not all melanomas on acral skin have a parallel ridge pattern. In asymmetrical combinations involving the pattern of furrows or the crossing pattern, the clues to melanoma are the same at acral locations as those

seen at other sites (5.52 right). As a general rule, the thicker a melanoma at an acral site, the more it resembles melanoma at other locations.

It may be difficult to distinguish between the structureless pattern and the parallel ridge pattern, when the lines in the ridge pattern are wide enough to almost occupy the furrows. When the distinction cannot be made with certainty, both possibilities should be followed in the algorithm.

Radial lines

Radial lines always occur in combination with other patterns. When the radial lines occupy the entire circumference of the lesion the combination of patterns is symmetrical. When assessing symmetry, pseudopods

and radial lines are considered equivalent. In practice, radial lines peripherally are found in combination with only two different patterns in the center; clods and structureless. When the center is structureless and white, the lesion is usually a dermatofibroma. When the center is structureless and brown, black or gray, the lesion is usually a Reed nevus (5.53, top row). In the latter case one may find brown or gray clods instead of the structureless center.

Asymmetry is necessarily created when peripheral radial lines do not occupy the entire circumference of a lesion but are present only in some segments. The primary differential diagnosis is then melanoma versus basal cell carcinoma (5.53 bottom row). The distinction

between these diagnoses is made on the basis of clues. Two arrangements of radial lines are strong clues to basal cell carcinoma. Peripheral radial lines in basal cell carcinoma usually have a common base, which is not usually the case in melanoma. Also, in basal cell carcinoma, radial lines are not only seen at the periphery, as in melanoma, but also within the lesion. In this case the radial lines do not just converge at the center but do so at a dot or a clod. These structures are usually multiple, and are possibly the most specific clue in dermatoscopy. Another feature often seen in basal cell carcinoma but only rarely in melanoma is radial lines extending from a hypopigmented structureless area (5.53 bottom right). Usually in melanoma radial

lines or pseudopods extend from pigmented reticular lines or from pigmented areas just as darkly pigmented as the radial lines/pseudopods.

Radial lines or pseudopods can also be seen in recurrent nevi (5.54). As a rule radial lines in recurrent nevi are arranged asymmetrically. They cover the entire circumference only rarely. As a general rule the pigmentation in recurrent nevi does not extend beyond the scar. The radial lines that are occasionally seen in pigmented Bowen’s disease are usually composed of brown or gray dots or coiled vessels in linear arrangement (14).

Curved lines

Once all other patterns of lines have been excluded, only curved lines remain. The pattern of curved lines is the least specific and therefore the last assessed of the patterns formed by lines. A combination of patterns that includes curved lines is almost always asymmetrical. When the color is only brown, the most likely diagnosis is solar lentigo or seborrheic keratosis (5.55). However, when any of the other colors of melanin (gray, blue or black) are present, melanoma must be ruled out before diagnosing either seborrheic keratosis or lichen planus-like keratosis.

Brown

Circles+

Partly gray

Solar Lentigo/seborrheic keratosis

Congenital nevus, “superficial” or “superficial and deep” Congenital nevus (Miescher nevus)

(Clark nevus, melanoma in situ)

Melanoma

Lichen planus-like keratosis

Pigmented actinic keratosis

5.2.2 Pseudopods

Pseudopods, like radial lines, are only seen in combination with another pattern. The only arrangement seen is with the pseudopods at the periphery and the other pattern in the center of the lesion. The pattern in the center is usually structureless, occasionally clods, and least often reticular lines. The distribution of the pseudopods at the periphery is far more important than the type of pattern in the center. Once again, when assessing symmetry, pseudopods and radial lines are considered equivalent. When the pseudopods are regularly distributed over the entire circumference (symmetrically) the lesion usually is a Reed nevus (5.56 left). However, when the pseudopods are only present in some segments of the periphery (asymmetrically), the diagnosis of melanoma must be considered (5.56 right).

Recurrent nevi sometimes have pseudopods at the periphery but usually they can be diagnosed easily based on the history and the presence of a scar (17, 18). When diagnosing lesions with pseudopods, variables other than dermatoscopy must be considered. Factors such as the patient’s age, skin type, number of nevi, their distribution and clinical appearance, and history of change, are all relevant to the diagnosis. While these factors may influence the diagnosis, they should not influence the dermatoscopic description. In other words, the same dermatoscopic pattern may lead to different conclusions in different situations. When one finds a pattern of pseudopods in a child, the diagnosis is almost certainly Reed nevus, regardless of whether the pattern is symmetrical or asymmetrical. In an adult, on the other hand, the diagnostician would be inclined to

favor melanoma and would be inclined to submit even symmetrical lesions for histopathology. There is nothing wrong with this, provided factors such as age do not influence the process of formulating a dermatoscopic description; there is ample opportunity to take these factors into account later in the diagnostic process. Our eyes are quite easily tempted and misled to see what we want to see, and preconceptions increase the chance that such errors of perception will occur.

Objectivity and independence from extraneous influences are essential aspects of pattern analysis. While this must be strictly applied in formulating descriptions, there is leeway in weighing the clues afterwards, such as described above for the assessment of pseudopods. Another example would be weighing the significance of gray dots as a clue to melanoma, which is of much greater significance in lesions on the face than at other locations on the body. This flexibility in weighing the clues is responsible for much of the power of pattern analysis, and learning the judicious application of this flexibility is one of the major roles of experience in dermatoscopy. On the other hand, this flexibility can generate difficulties for beginners, so in general beginners should be more strict than experts in their application of pattern analysis. Flexibility in weighing clues does not mean that one may twist and turn all of one’s observations until one reaches the diagnosis formed in the first second. The art lies in knowing how far one can go in the process of interpretation, and then stopping.

5.2.3 Circles

Once lines and pseudopods have been excluded, the pattern of circles is the next most specific pattern. The pattern of circles is the typical pattern of facial skin, but it may be found at any location. Sometimes it may be difficult to distinguish between a pattern of closely adjacent circles and reticular lines; in fact, the two patterns are often seen together, both on the face (reticular lines may be seen on the face) and elsewhere. When these patterns co-exist, the lesion should be analyzed by reticular lines, the more specific pattern. The only common symmetrical combination of circles with another pattern is that of peripheral brown circles combined with a structureless zone (or less often white lines) centrally, seen in dermatofibroma. Other combinations that include the pattern of circles but no lines are nearly all asymmetrical, so the color of the circles becomes more important than assessment of symmetry. If the color is only brown, one must consider a solar lentigo or a seborrheic keratosis on the one hand, and a “superficial” or “superficial and deep” congenital nevus or a Clark nevus on the other. Occasionally a Miescher nevus may also have brown circles. If any of the circles are gray, the differential diagnosis includes melanoma (5.57, 5.58), lichen planus-like keratosis and, especially on facial skin pigmented actinic keratosis. Occasionally facial melanomas will present with brown circles, without any grey color. This means that melanoma is always in the differential diagnosis of pigmented circles on the face, regardless of their color (8).

5.2.4 Clods

The next pattern in order is clods. Because lesions to be analyzed by the pattern of clods lack lines, pseudopods and circles (otherwise the lesion would be analyzed by these more specific patterns), the only combinations to be considered are clods plus dots and clods plus structureless. Clods and structureless may be combined with each other symmetrically or asymmetrically. In cases of a symmetrical combination

the structureless zone is in the center of the lesion while the clods (which are usually brown) are seen at the periphery (5.59).

When the center is skin-colored the lesion is most probably a “superficial and deep” congenital nevus, more rarely a Spitz nevus. When the structureless center is brown or black, the diagnostician should first consider a growing “superficial and deep” congenital nevus (commonly in children) or a pigmented Spitz

nevus. In cases of a blue structureless center, the first entity to be considered is a combined congenital nevus (5.60 right).

Asymmetrical combinations of patterns containing clods but no lines, pseudopods or circles are analyzed differently depending on whether the colors are predominantly those of melanin, or those of another pigment (5.61).

Lesions pigmented by melanin are predominantly black, brown, gray or blue. Black pigmentation can be caused by coagulated blood as well as melanin, so the interpretation of the color black depends on what other colors are present. When the colors brown, blue or gray are predominant in the remainder of the lesion, the color black is best interpreted as melanin in the stratum corneum. However, when red or purple is predominant, the color black is best interpreted as coagulated blood.

Lesions with no pigment, or with pigments other than melanin predominant, are assessed based on the color of the clods, and not on the color of the rest of the lesion. A predominance of white or yellow clods is indicative of a seborrheic keratosis. Orange clods in large numbers also indicate a seborrheic keratosis but when only a very few are present, basal cell carcinoma must also be considered. The orange clods of basal cell carcinoma are simply serum crusts arising from erosion or ulceration, so red inclusions (representing blood) within the clods are common. As serum crusts

are sticky, fibers of clothing may become adherent to them and serve as an indirect sign of ulceration. Red or purple clods usually indicate a hemangioma or a vascular malformation, but may also signify a melanoma or metastasis of melanoma when occurring in combination with another pattern. In particular, hemangioma should not be diagnosed when vessels as lines or dots are seen within the red clods.

When melanin is the predominant pigment, the color of the whole lesion is assessed, and not just the clods. When the lesion is one color, brown, the diagnostician should consider a “superficial and deep” congenital nevus or a Spitz nevus. When other colors are also present the diagnostician should consider a basal cell carcinoma or a melanoma in addition to a seborrheic keratosis and its variants (5.62). The distinction between these three differential diagnoses is made, as mentioned earlier, on the basis of additional clues.

5.2.5 Dots

When all other patterns have been excluded, only dots remain (5.63). In the algorithm we are currently in the category of “more than one pattern”. Thus, all lesions that now follow consist of dots and a structureless zone. As structureless is the least specific pattern, the diagnostic process is mainly based on the color of dots, meaning that the algorithm for “dots and structureless” differs only slightly from the algorithm for “dots”.

Stepwise procedure

1. Gray dots

2. Blue dots

Dots+

3. Black dots

4. Brown dots

Lichen planus-like keratosis Pigmented actinic keratosis Pigmented Bowen‘s disease Melanoma, regressive Basal cell carcinoma

Basal cell carcinoma

Melanoma

Clark nevus

Clark nevus Congenital nevus Solar lentigo

Pigmented Bowen‘s disease

Gray dots may signify a melanoma (5.64 right), a lichen planus-like keratosis, a pigmented superficial squamous cell carcinoma (actinic keratosis or Bowen’s disease) or a basal cell carcinoma. Of these differential diagnoses, the basal cell carcinoma can be differentiated most easily from the others on the basis of additional clues. Blue dots are quite specific

for basal cell carcinoma (5.64 left). Usually there also will be additional clues to support this diagnosis. Black dots are uncommon but should cause the investigator to think of melanoma, and prompt a search for other clues to this diagnosis. Brown dots are found in solar lentigo and pigmented Bowen’s disease. Very rarely a Clark nevus may have just brown dots and a struc-