4 курс / Дерматовенерология / Дерматоскопия (3)

Figure 6.13: Basal cell carcinoma with polarizing specific white lines and clods

Figure 6.14: Basal cell carcinoma with four-dot clod (for white dots arranged in a square)

6.2 Vascular patterns

In dermatoscopic assessment of pigmented lesions, blood vessel morphology is only ever accorded the status of being a clue to diagnosis, as patterns formed by vessels (20) are less specific and hence less important than pigment patterns and colors. The patterns formed by blood vessels are no more diagnostically specific in amelanotic lesions, but in the absence of melanin pigment, analysis of vessel patterns must assume greater importance.

The pattern of vessels is assessed using the principles detailed in chapter 3. Vessels may be seen as dots, clods or lines (6.19). Lines may be straight, curved, looped,

serpentine, helical or coiled. When one vessel type predominates, this is called a “monomorphous” pattern of vessels. When more than one type of vessel is seen, the pattern is called “polymorphous”. In addition to the type of vessels, their arrangement – both how vessels are arranged relative to each other, and how vessels are distributed throughout the lesion – may also be of diagnostic significance (6.20).

In the majority of cases, vessels appear to be distributed randomly, i.e. not arranged in any specific manner throughout the lesion. Vessels as dots or coils may be arranged in straight lines (linear arrangement) or in serpentine lines (serpiginous arrangement). When vessels as dots or coils are not uniformly distributed but

are denser 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”. Straight linear vessels that intersect each other nearly at right angles have a “reticular” arrangement. 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”.

Vessel morphology varies with lesion thickness. The capillary loops that rise from the superficial vascular plexus and extend towards the surface of the skin may appear as dots or curved or looped lines, depending on the angle from which they are viewed (6.21). In flat lesions, most vessels are viewed end on and so appear as dots or short curved lines. As a lesion becomes thick-

er, there is a tendency for more vessels to be viewed obliquely and thus seen as loops. As malignant neoplasms become thicker, neovascularization becomes more common.

This variation means the same vessel morphology may have different diagnostic significance in nodules compared to flat lesions.

6.3 Differential diagnosis of non-pigmented lesions

General principles

As a general principle, even in a largely non-pigmented lesion, if there is any pigment at all that can be attributed to melanin (black, brown, blue or gray) one should first attempt to diagnose a lesion using a pigmented lesion algorithm (6.22). Only if there truly is no pigment or if the pigmented features present are non-specific, should a non-pigmented algorithm be used. The meth-

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B

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Figure 6.21: Vessels in flat and raised lesions.

The capillary loops that rise from the superficial vascular plexus and extend towards the surface of the skin may appear as dots or curved or looped lines, depending on the angle from which they are viewed.

Figure 6.22: Pigment first.

Examine “non-pigmented” lesions carefully for any pigment before using a non-pigmented algorithm. On close inspection, two areas of converging radial lines are apparent, allowing a confident diagnosis of basal cell carcinoma.

od we present requires the integration of clinical and dermatoscopy features to reach an acceptable level of diagnostic accuracy.

As a matter of convenience, clinical features are usually assessed before dermatoscopy. These findings are then included in the diagnostic process as one proceeds with dermatoscopy.

The main features assessed clinically are whether the lesion is flat or raised; whether it is solitary or one of many; and the presence or absence of ulceration, scale, and keratin.

It is critical to differentiate between flat and raised non-pigmented lesions. When we speak of flat lesions we do not mean that the lesion must be so flat as to be impalpable. Rather, a lesion is termed flat when the horizontal diameter greatly exceeds height. Macules, flat papules and patches are flat whereas elevated papules and nodules are raised.

While it is true that neoplasms tend to be solitary and inflammatory conditions tend to be multiple, this is not always the case. In particular, actinic keratosis is often multiple. Most critically, a solitary non-pigmented neoplasm – most commonly Bowen’s disease, but rarely even a non-pigmented melanoma – may be concealed amongst multiple patches of psoriasis.

As already mentioned, ulceration does not suggest a specific diagnosis but should (in the absence of trauma) prompt the consideration of malignancy.

Scale is an important hallmark of Bowen’s disease and actinic keratosis but is obviously also found in inflammatory conditions. On the rare occasions scale is seen in superficial basal cell carcinoma or melanocytic lesions, it is usually a consequence of irritation such as rubbing or scratching. Occasionally nevi show a spongiotic reaction that leads to scaling (21). With severe chronic sun damage, the entire skin surface may be scaly, including that overlying lesions.

If keratin is present, the main differential diagnoses include well-differentiated squamous cell carcinomas/ keratoacanthomas, seborrheic keratoses and viral warts (22). Keratin can also be found in Unna or Miescher nevi (keratin plugs on the surface between papillomatous invaginations), in keratinizing adnexal proliferations such as pilomatrixoma (subsurface keratin) (23), in keratinizing cysts (subsurface keratin), and in angiokeratoma (surface keratin) (24). After clinical assessment one then proceeds to dermatoscopy.

Dermatoscopy of non-pigmented lesions

The first step in assessing non-pigmented lesions is to decide whether they are flat or raised. The vascular pattern is more diagnostically significant in flat lesions than in raised lesions. In raised lesions, other clues (ulceration, keratin, and white clues) take priority over vessel pattern analysis, just as pigmented structures take priority for pigmented lesions.

Flat non-pigmented lesions

Because nearly all pigmented lesions may also appear in a non-pigmented form, the differential diagnosis for flat non-pigmented lesions encompasses nearly the entire spectrum of melanocytic and non-melanocytic lesions discussed in chapter 2. In addition to this spectrum of neoplasms, various inflammatory skin diseases must also be considered. Melanocytic lesions that may appear as non-pigmented skin-colored to red macules or patches are Clark nevi, “superficial” or “superficial and deep” congenital nevi, Spitz nevi and, of course, melanoma. Keratinocytic cancers (actinic keratosis, Bowen’s disease, superficial basal cell carcinoma) and many inflammatory skin diseases, for example psoriasis, nummular dermatitis, porokeratosis, lupus erythematosus and lichen planus occur mainly as flat pink lesions. We will discuss the dermatoscopic appearance of inflammatory lesions in greater detail in chapter 8. Rarely, even seborrheic keratosis and dermatofibroma may be flat and non-pigmented. The most common flat non-pigmented lesions and their appearance on dermatoscopy are shown in table 6.2.

If vessels are seen, there is a relatively simple algorithm for flat non-pigmented lesions, starting with the assessment of vascular patterns (6.23). While it has proved useful in the hands of the authors, it lacks the specificity of algorithms to assess pigmented lesions. It should also be seen as evolving, rather than an algorithm carved in stone.

Next, one decides whether the vascular pattern is monomorphous or polymorphous.

When there is a monomorphous pattern of vessels, a distinction is made between vessels as dots, clods, and vessels as lines. In cases of vessels as dots, the differential diagnosis comprises Bowen’s disease, inflammatory skin diseases such as psoriasis, and benign melanocytic lesions. There are exceptional cases of flat amelanotic melanomas on chronic sun-damaged skin that have a monomorphous pattern of dots, but a flat amelanotic melanocytic lesion with a monomorphous vascular pattern of dots is nearly always a nevus.

Scale (not always visible on dermatoscopy) is usually present in inflammatory lesions and Bowen’s disease but not in melanocytic lesions. Further differentiation is then performed as far as possible on the basis of the clinical context and additional clues. The scale of psoriatic lesions is practically always white, whereas the scale of different types of dermatitis (for example nummular dermatitis or seborrheic dermatitis) is mixed with serum and appear yellow or orange (25). The scale of porokeratosis usually presents as a peripheral rim (26, 27) that should not be confused with delicate peripheral pigmentation of some flat basal cell carcinomas. The differentiation between psoriasis and Bowen’s disease (intraepidermal carcinoma) can be challenging. The vessels of Bowen’s disease are usually coils (28) and those of psoriasis usually dots (29) (6.24). Sometimes, however, the coils of Bowen’s disease are so small

Clues

Face: In the center of the circular erythema there is a yellow or an orange clod; white circles; 4 white dots arranged in a square (polarized dermatoscopy); scale

Coiled vessels arranged in clusters or in lines; scale

Polarizing-specific (perpendicular) white lines; ulceration; adherent fiber sign may confirm ulceration

No scale

White dots; white, yellow or orange clods

None

Central red dot, sometimes pulsating

White structureless area or white lines in the center

White scale Peripheral scale Yellow scale

White circles, white structureless zones (advanced lesions with sclerosis)

Ring-shaped scale at the periphery (cornoid lamella)

Thick white or skin colored lines (Wickham striae)

No scale, flat (macule)

No scale, usually raised on the center

No scale, occasionally white or skin-colored lines, slightly raised

No scale, white lines, remnants of pigmentation dermatoscopically (especially brown structureless zones)

that the vessels appear as dots and in long standing, elevated lesions of psoriasis the vessels may appear as coils. In psoriasis the vessels tend to be randomly distributed over the lesions whereas in Bowen’s disease they tend to be arranged in clusters or lines. In contrast to Bowen’s disease (often dull white or yellow scales) the scales of psoriasis tend to be shiny white.

As discussed in Chapter 3, a monomorphous pattern of red clods (vessels as clods) indicates a hemangioma or a vascular malformation.

As well as Bowen’s disease, coiled vessels may be seen in psoriasis, lichen simplex chronicus, and other inflammatory diseases. Serpentine vessels are seen in superficial basal cell carcinoma (6.25), but this diagnosis is more reliable when other specific clues to basal cell carcinoma are present.

The reticular pattern of vessels is not included in the algorithm because it is too unspecific (it occurs, for instance, on chronic sun-damaged skin). Thin reticular vessels are found in lesions of a specific type of mastocytosis,

telangiectasia macularis eruptiva perstans (30–32). Thick reticular vessels are found in “spider nevus” (nevus araneus). A central dot vessel (the supplying arteriole) is commonly seen, sometimes with visible pulsations. Dermatofibromas are occasionally non-pigmented (4). If they are flat they usually show a vascular pattern of dots or coils, and may also show a typical central white structureless area or central polarizing-specific white lines.

When the vascular pattern is polymorphous, one should proceed in a stepwise manner, as in cases of pigmented

lesions with more than one pattern. The investigator first determines whether vessels as dots are present. As in all vascular patterns, a few vessels as dots are not significant; to constitute a pattern they must cover a significant part of the lesion. In 6.26 and 6.27 we show flat non-pigmented lesions with (6.26) and without (6.27) vessels as dots. If the vascular pattern is polymorphous and includes vessels as dots (figure 6.26, middle and bottom row) a melanoma cannot be excluded with certainty and the lesion should be submitted for histopathology. If it is difficult to decide

whether the pattern is one of dots or small coils, it is prudent to assume they are dots and thus keep melanoma in the differential diagnosis.

When there are no vessels as dots but polymorphous linear vessels (including coiled, serpentine, and looped vessels) the investigator should consider superficial basal cell carcinoma, Bowen’s disease or seborrheic keratosis. In cases of superficial basal cell carcinoma the predominant structures are thin serpentine vessels (33), whereas Bowen’s disease is marked by coiled vessels (28). Ulceration is more common in flat basal

cell carcinomas, scale is more common in Bowen’s disease. Seborrheic keratosis may have all types of vessels as lines, including looped vessels (34). However, in most cases there will be one or more of white dots and white, yellow or orange clods.

When no vessels are visible or when a diffuse erythema is seen in a flat lesion, dermatoscopy is of no significant benefit unless other clues are present. Actinic keratoses (6.28) often have an erythematous background without discernable vessels. Facial actinic keratosis may have white circles (8), but white circles should also lead to