The dermoscopic examination of vascular lesions, including hemorrhages due to trauma, is of paramount relevance, because melanomas can be excluded with a high level of certainty. The following entities will be discussed in detail: hemangioma, angiokeratoma, subungual hemorrhage, and subcorneal hemorrhage. From a dermoscopic point of view the lowest common denominator of all these lesions is their reddish, reddish-blue to reddish-black coloration in the complete absence of pigment network structures and other melanoma-specific criteria.
Hemangioma
The term hemangioma comprises various solitary vascular proliferations, such as arteriovenous hemangioma (cirsoid aneurysm), capillary aneurysm (thrombosed capillary aneurysm), cherry angioma (senile angioma), pyogenic granuloma, and venous lake, that may occasionally simulate a melanoma and therefore are often examined dermoscopically. Solitary lymphangioma is also mentioned here, since its dermoscopic features are basically identical with the so-called hemangioma group. Classic capillary and cavernous hemangiomas, commonly found in neonates, are not considered here, because the lesions are diagnosed clinically and dermoscopic examination is usually not performed.
Dermoscopically, the lesions reveal a typical lacunar pattern, although in some instances, e.g. venous lake or pyogenic granuloma, the lacunar pattern cannot be easily recognized. Actually, the venous lake more often has a homogeneous pattern and pyogenic granuloma may show a multicomponent pattern. The dermoscopic hallmark of the hemangioma group is the presence of several to numerous, roundish or oval areas with a reddish or red-bluish coloration. These red lacunas (also called red lagoons) are virtually pathognomonic for hemangiomas. Since the underlying histopathologic substrate is often situated in the superficial dermis and not immediately beneath the epidermis, as in angiokeratoma, these lacunas are not really sharply circumscribed.
Angiokeratoma
The term angiokeratoma encompasses several, unrelated conditions characterized by the combination of vascular proliferations and hyperkeratosis. The different types of angiokeratomas are the following: solitary angiokeratoma, angiokeratoma circumscriptum, angiokeratoma of Fordyce (angioma of scrotum and vulva), angiokeratoma of Mibelli, and angiokeratoma corporis diffusum (Fabry’s disease). With regard to dermoscopy of pigmented skin lesions only solitary angiokeratoma is pertinent. From a clinical point of view, the solitary angiokeratoma is a small, warty, red-blue to black papule that may appear on any anatomic site with predilection for the lower extremities. It can be regarded as a ‘pseudomelanoma’, since clinically it simulates melanoma.
Dermoscopically, solitary angiokeratoma is characterized by a lacunar or multicomponent pattern composed of large, several to numerous, sharply demarcated, roundish or oval areas with a reddish, red-bluish or dark-red to black coloration. These red lacunas are very distinctive and together with whitish-yellowish keratotic areas are diagnostic for angiokeratomas. Another dermoscopic feature frequently found in angiokeratoma is the presence of a whitish veil due to the acanthotic epidermis with hypergranulosis and compact orthokeratosis. Since this whitish veil is not associated with any pigment network or any other melanoma-specific criteria, it is not considered in the diagnostic algorithm at all. Not infrequently is a reddish halo found around an angiokeratoma as a consequence of recent trauma.
Subungual Hemorrhage
Nail hemorrhage frequently occurs following trauma to the nail. Obviously, the extent of such a subungual hemorrhage depends on the intensity and force of the trauma. However, patients seeking the advice of a physician because of subungual hemorrhage never recall any trauma or even think of the possibility of a trauma, because otherwise they would not seek consultation. The main clinical differential diagnoses of subungual hemorrhages are subungual nevi, subungual melanomas and, rarely, infections with fungi or bacteria, e.g. pseudomonas.
Clinically, subungual hemorrhages are characterized by variously sized, round to oval, sharply circumscribed, usually jet-black areas.
Interestingly enough, at dermoscopic examination the jet-black clinical pigmentation appears lighter and reveals a red-black or even dark-red color, suggestive of hematoma. Moreover, adjacent to the sharply demarcated, structureless, dark red areas, some tiny, roundish, reddish dots may be recognized that on clinical examination are not visible. Moreover, in some instances the nail plate overlying the subungual hematoma shows a slight roughness upon dermoscopic examination.
Subcorneal Hemorrhage
Subcorneal hemorrhage, also called black heel, talon noir or subcorneal hematoma, is seen commonly on the heels of young individuals involved in sport activities such as tennis, basketball or soccer. Of course, it is also found on the palms, resulting from lateral forces due to other sport activities, e.g. tennis, golf or mountain climbing. As is the case with subungual hemorrhage, individuals seeking medical advice never ever recall any trauma. Within a few weeks, or within a few months when the soles are involved, subcorneal hemorrhage resolves spontaneously.
Clinically, subcorneal hemorrhage represents an asymptomatic sharply circumscribed, homogeneous, red-black to jet-black macule. As is the case with subungual hemorrhage, the reddish coloration of subcorneal hemorrhage can be much better appreciated when performing dermoscopy, which allows a reliable diagnosis to be made in most instances. Although the global pattern is usually homogeneous or globular, in some cases the pigmentation is more pronounced and follows the cristae of the glabrous skin, revealing a somewhat parallel pattern. A nearly similar parallel pattern, called ‘parallel-ridge pattern’, however, has recently been described in acral melanoma in situ by Oguchi et al. [Arch. Dermatol 1998], whereas in acral nevi the parallel pattern following the sulci of glabrous skin is named ‘parallel-furrow pattern’. So, even when using dermoscopy, at least in rare cases, the differentiation between subcorneal hemorrhage on the one hand and acral melanoma in situ on the other hand may be difficult and a punch biopsy with subsequent histopathologic examination may be necessary.