【综述】有特殊特征的黑素细胞痣:临床皮肤镜和反射式共聚焦显微镜表现(3)

Targetoid haemosiderotic nevus

Clinical features  The occurrence of traumatic changes is frequent in melanocytic nevi, particularly in those that are elevated or exophytic (globular nevi). Mechanical irritation, even not apparent, by clothing, shaving or scratching is most common causes of injury.Targetoid haemosiderotic nevus (THN) is reported by patients as a sudden change in pigmentation in a previously known nevus, and it is very frequent that they do not recognize the injury. Tenderness and itching are common symptoms. The typical clinical appearance is the sudden development of an asymptomatic ecchymotic, violaceous halo causing a target-like phenomenon around a long-lasting central elevated nevus. It presents more often in children and young adults, usually localized on the upper part of the thorax. Patrizi et al. propose that the rarity of THN is due to its spontaneous and rapid regression. The major differential diagnosis is with targetoid haemosiderotic haemangioma (THH) that clinically presents as a single, small, annular target-like lesion on the trunk or an extremity of young adults. Other differential diagnoses include melanoma, traumatized angiokeratoma, haemosiderotic dermatofibroma and cockade nevus.

Regarding histopathology, fibrin deposits, extravasates of erythrocytes and an increased number of ectatic blood vessels with hobnail endothelial cells are seen, amalgamated with nevus cells. Peripheral halo is characterized by extensive haemorrhage and haemosiderin deposits in concert with irregular, thin-walled, slit-shaped vascular channels that dissect between collagen bundles of the papillary dermis. A mild inflammatory infiltrate mainly composed by eosinophils is observed. After the eczema disappears, only scant haemosiderin deposits, fibrosis and few collapsed vascular lumina in the papillary and mid-reticular dermis are seen.

Dermoscopy  Targetoid haemosiderotic nevus shows the typical features of globularmelanocytic nevus with vascular haemorrhagic (red to purple or black) changes superimposed on the nevus and particularly surrounding it: especially irregularly sized and shaped, jet-black areas and often comma-shaped vessels can be seen. The targetoid halo demonstrates a pale, ill-defined inner area surrounded by a homogeneous reddish zone with peripheral-jagged margins. In the evolution, the central nevus persists and the ecchymotic halo ultimately disappears, with no tendency to recur. Dermoscopy is very helpful to differentiate blood from melanin pigmentation, and helps to differentiate THN fromTHH (Fig. 9).

Reflectance confocal microscopy  There is no description in the literature of a THN, up to date. Herein we report on a case, where RCM was able to show the features of a compound nevus, with presence of a ringed pattern at the periphery and dense and sparse nests. In the superficial dermis nevus cells and melanocytic nests were amalgamated with extravasated erythrocytes and inflammatory cells (Fig. 9).

Management  One or two weeks of treatment with local anti-inflammatories or a heparinoid cream is recommended to facilitate the regression of the phenomenon. If the nevi do not recover a typical appearance within a month, surgical excision should be performed.

Uncommon variants

Desmoplastic nevus

Clinical features  Desmoplastic (sclerotic) nevus is an infrequently reported, poorly characterized, benign melanocytic proliferation, with only few case series published to date. Clinically, DN is usually a small (up to 1 cm in diameter), flesh-coloured, erythematous, or slightly pigmented papule or nodule often occurring on the extremities of young adults (average age, 30 years), with a slight female predominance. Histopathologically, DN are characterized by spindle-shaped or epithelioid melanocytes, with readily appreciable pseudonucleoli embedded within a fibrotic stroma. DN is included in the spectrum of dermal proliferations with a desmoplastic component composed by dermatofibroma, sclerotic blue nevus, desmoplastic SN, DN and desmoplastic melanoma. Their differentiation can sometimes represent a diagnostic dilemma for both clinicians and histopathologists.

Dermoscopy  Dermoscopically, only three cases have been described up to now, exhibiting a tiny light brown network lying on a pinkish erythematous background. DN is usually symmetric in colour and structure and devoid of any melanoma-specific criteria. Features shared by dermatofibroma and DN include their location on the extremities and their size ranging between few millimetres and 1 or 2 cm. Clinically, both lesions appear as firm papules or nodules that may sometimes cause clinical symptoms such as pain or itch. However, clinical dimpling sign and the dermoscopic central white patch surrounded by a delicate pigment network are specific features of dermatofibroma that were not seen in our cases of DN (Fig. 10).

Reflectance confocal microscopy  Reflectance confocal microscopy features of desmoplastic nevus have not been yet described. Here, we present one case, showing a regular honeycombed pattern in the superficial layers, with no atypical cells nor pagetoid spread. At the level of DEJ regularly shaped edged papillae were visualized. No features of the underling dermal proliferation were detectable by means of confocal microscopy (Fig 10).

Management  In most of the cases, DN are removed because a history of changes and because of their unusual dermatoscopic features. Main differential diagnosis is with desmoplastic melanoma, which is more frequently seen in old patients on sunexposed areas.

White dysplastic nevus

Clinical features  Up to date, five patients with white dysplastic melanocytic nevi (DMN) have been described. These nevi appear clinically as white to pale red macules with accentuated skin markings and a silvery ‘shining’ appearance when observed with tangential light. Clinical differential diagnosis of these white DMN include idiopathic guttate, flat warts, hypomelanosis, anetoderma, pityriasis alba, hypopigmented mycosis fungoides, vitiligo, post-inflammatory hypopigmentation, lichen sclerosus et atrophicus, superficial morphea and leprosy. The silvery shine seen under tangential light is a clue for clinical diagnosis of white DMN. Notably, of the five patients with white DMN, four patients had a melanoma with two of them presenting with two primary amelanotic melanomas. The association of white DMN with multiple primary amelanotic melanoma is significant given that primary amelanotic melanoma is rare, with the largest series suggesting an incidence of <2% of all melanomas. Herein, we present an additional case of white DMN associated with melanoma in a 69-year-old women, who presented with a superficial spreading melanoma (0.5 mm thickness) on the back. Close to the primary melanoma, a silvery shining roundish macule was seen, which has been histopathologically diagnosed a dysplastic nevus. Histologically, this lesion showed an increased number of atypical melanocytes with hyperchromatic and pleomorphic nuclei, arranged as solitary units and in nests, mainly at the DEJ and the papillary dermis (Fig. 11).

Dermoscopy  There are no reports of the dermoscopy of these lesions due to complete absence of pigmentation.

Reflectance confocal microscopy  There is no description on white dysplastic nevi up to know.

Management  To rule out white DMN, biopsy should be taken from patients who present with white to pale-red macules with accentuated skin markings, which cannot be clearly classified. In addition, special attention should be paid to the possible association of white DMN with melanoma.

Clinical features  Balloon cell nevus is a well-recognized histological entity, having a clinical presentation that is not distinctive. Histologically, BCN is characterized by a predominance or complete occurrence of large, vesicular, clear cells, called balloon cells. Balloon cells are defined as melanocytes with pale-staining and vacuolated cytoplasms, which often have a defect in melanosome formation.

The most common site of the lesion appears to be the head and neck area, followed by the trunk and extremities. Male to female ratio is almost 1: 1 similar. BCN presents mainly in the first three decades of life and it is usually asymptomatic, generally brown and may appear as a smooth papule or may be polipoid.

Dermoscopy  Dermoscopy of BCN have been described previously only in the colour atlas by Stolz et al. and in recent report by Jaimes et al., revealing numerous aggregated white globular structures that correspond to ballon cell nevi nests (Fig. 12).

Reflectance confocal microscopy  Balloon cell nevus have never been described in RCM. Here, we describe one case in which white globular structures correspond to melanocytic nests. Melanocytes within the nests are characterized by the presence of a vacuolized cytoplasm, visible as shiny areas surrounding a dark nucleus (Fig. 12).

Management  Balloon cell nevus is considered a benign lesion and management should be conservative.

Conclusion

Melanocytic nevi may sometimes display features deviating from well-characterized aspect of junctional, compound or dermal nevi. Peculiar histopathological subtypes or traumatic, inflammatory or immunodriven phenomena may result in unusual clinical presentations of common nevi. Recognition of clinical, dermoscopic and when available, RCM features of these nevi may be helpful in everyday clinical practice to improve diagnostic accuracy.

由MediCool医库软件涂秀丽 吴茵芸编译，上海市皮肤病医院陈裕充博士审核

原文来自：JEADV 2014, 28, 833–845