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American Journal of Dermatopathology:
doi: 10.1097/DAD.0b013e3181bd912f
Letter to the Editor

Angiomatoid Intradermal Melanocytic Nevus or Chimeric Nevus?: A Potential Diagnostic Pitfall

Martín, José M MD*; Calduch, Luis MD*; López, Verónica MD*; Jordá, Esperanza MD, PhD*; Monteagudo, Carlos MD, PhD†

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*Department of Dermatology, Hospital Clínico Universitario, Valencia, Spain; †Department of Pathology, Hospital Clínico Universitario, Valencia, Spain.

To the Editor:

A prominent vascular component has been rarely described in melanocytic lesions. Diaz-Cascajo et al1 were the first to report a particular variant of desmoplastic Spitz nevus with a striking fibrous stroma and many densely arranged small blood vessels. Due to its similarity to a vascular tumor, they proposed the term of “angiomatoid nevus” for this condition. Since then, few similar cases have been described, corresponding almost exclusively to Spitz nevi.2,3 To the best of our knowledge, there is only one report of angiomatoid cellular blue nevus,4 and we have not found any case of junctional, compound, or intradermal angiomatoid melanocytic nevus.

We recently observed a 53-year-old woman, with a progressively enlarging nodule, located on her right lumbar area, which was present for 7 years. The lesion measured 13 mm in diameter. It had a slightly pigmented and shiny surface. Telangiectasias could also be appreciated.

Dermoscopically, the lesion showed a background of light brownish pigment, with a prominent vascular pattern composed by arborizing vessels and hemorrhagic areas that were surrounded by a striking whitish veil, which was especially located in the central part of the lesion (Fig. 1).

Figure 1
Figure 1
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We excised the lesion, and histologically, an intradermal melanocytic congenital type nevus was found. Several medium size vessels with thin fibrous wall, and red blood cell content were also found (Fig. 2). Significant subepidermal collagenous fibrosis was present above the vessels (Fig. 3). A cystic sudoriparous duct was present in association with the melanocytic proliferation in the lower part of the lesion.

Figure 2
Figure 2
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Figure 3
Figure 3
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A prominent vascular component is present histologically in a variety of tumors. In spite of this, a vascular striking component is not frequent in melanocytic lesions, although they commonly display pseudovascular features.4

Angiomatoid nevus is characterized by its distinctive fibrovascular stroma. It was initially described in Spitz nevus. To date, 13 cases have been characterized in the literature (12 corresponding to Spitz nevus and 1 to cellular blue nevus).1-4

In angiomatoid Spitz nevus, there is a proliferation of numerous small blood vessels with plump endothelia, resembling a vascular tumor. Melanocytes are embedded in a fibrous stroma composed of thick collagen bundles distributed haphazardly. In all cases, the stroma showed large numbers of small thick-walled blood vessels with round to oval lumina lined by plump endothelial cells with monomorphous nuclei devoid of atypia. Mitotic figures were rare or absent. The vessels were distributed in clusters or as solitary units throughout the stroma, and they were preferentially located in the upper part of the lesions. A variably prominent, mostly perivascular, or diffusely distributed lymphoplasmacytic infiltrate, was noted in association with these prominent vessels. This lymphocytic infiltrate was composed predominantly of small, mature lymphocytes.1,2

The reported case of cellular blue nevus displayed a prominent angioma-like appearance due to the presence of numerous ectatic vessels throughout the neoplasm. Vessels were lined by flattened endothelium, incompletely filled with red blood cells and fibrinous material, and also showed fibrinous hyalinized walls of variable thickness. They were associated with irregular pseudovascular spaces, devoid of endothelial lining and directly delimited by neoplastic melanocytes. The size of these vessels was higher and they were less numerous compared with those appreciated in angiomatoid Spitz nevus.4

The ectatic vessels found in our case are similar to those reported by Urso and Tinacci,4 and they were surrounded by a striking fibrous stroma that was also present in the subepidermal area. Clinically, the lesion was also a large nodule located in the lumbar area. Interestingly, dermoscopically, it showed a striking vascular pattern composed of large-sized vessels, which were embedded in a whitish veil that corresponded histologically with the significant fibrosis present in the papillary dermis and surrounding vessels.

Regarding its developmental origin one might consider the combination of what appears to be the equivalent of a vascular malformation or anomaly, for example, a superficial arteriovenous malformation, and a dermal melanocytic nevus. Perhaps the lesion could be a developmental anomaly with 2 components: vascular and melanocytic rather than 1 alone. Such a lesion might fall, therefore, under the rubric of a chimeric nevus. In this patient, the vascular pattern was only present in the raised lesion, and the adjacent back was devoid of any vascular structure suggestive of an extensive vascular malformation. Moreover, although histological features suggest a congenital origin, the patient reported that it appeared 7 years ago.

Nonetheless, many nevi exhibit relatively prominent vascular components and this simply may be an exaggerated version of a common nevus with prominent vascularity, although the combination of the prominent vascularity with the striking fibrosis is extremely rare.

The causes that would provoke this fibrosis and vascular proliferation remain unknown. In our case, the location of the raised lesion on the lumbar region, made it susceptible to repeated trauma. There are entities such as atypical decubital fibroplasia in which there is also a prominent myxoid stroma rimmed by ectatic, thin-walled vascular channels as the consequence of continued pressure of the skin against the subjacent bone.5

We do not have an explanation for the fact that angiomatoid nevi affect almost exclusively women (13/14 cases). Hormonal factors might be involved as benign vascular lesions such as acquired angiomas can be affected by hormonal alterations due to pregnancy or contraceptive treatments.6

Although sometimes angiomatoid nevi may enter the differential diagnosis of melanoma, clinically, dermoscopically, or histologically,2,3 the absence of recurrences or metastases after complete excision in all cases reported supports the benign behavior of this lesion.

José M. Martín, MD

Luis Calduch, MD

Verónica López, MD

Esperanza Jordá, MD, PhD

Department of Dermatology, Hospital Clínico Universitario, Valencia, Spain

Carlos Monteagudo, MD, PhD

Department of Pathology, Hospital Clínico Universitario, Valencia, Spain

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REFERENCES

1. Diaz-Cascajo C, Borgui S, Weyers W. Angiomatoid Spitz Nevus: a distinct variant of desmoplastic Spitz nevus with prominent vasculature. Am J Dermatopathol. 2000;22:135-139.

2. Tetzlaff MT, Xu X, Elder DE, et al. Angiomatoid Spitz nevus: a clinicopathological study of six cases and a review of the literature. J Cutan Pathol. 2009;36:471-476.

3. Fabrizi G, Massi G. Angiomatoid Spitz nevus: a close simulator of regressing malignant melanoma. Br J Dermatol. 2001;145:845-846.

4. Urso C, Tinacci G. Angiomatoid cellular blue nevus: a variant of blue nevus with an angioma-like appearance. J Cutan Pathol. 2005;32:385-387.

5. Montgomery EA, Meis JM, Mitchell MS, et al. Atypical decubital fibroplasia. A distinctive fibroblastic pseudotumor occurring in debilitated patients. Am J Surg Pathol. 1992;16:708-715.

6. Schmutz JL. Physiological skin changes during pregnancy. Presse Med. 2003;32:1806-1808.

© 2010 Lippincott Williams & Wilkins, Inc.

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