Introduction
Solitary circumscribed neuromas (SCNs), also called palisading encapsulated neuromas, are a rare subset of benign peripheral nerve sheath tumors characterized by nodular proliferation of nerve fibers with Schwann cells without the predominance of axons.1,2 The typical presentation is that of a solitary papule composed of nerve tissue characterized by its fascicles of spindle cells and its encapsulation histologically.1,2 Common sites of occurrence have been described as the face and mucosa of the glans penis, nasal fossa, and oral cavity.2, 3, 4, 5, 6, 7, 8 Dermoscopic evaluation of skin SCNs has been documented in 6 prior reports for a total of 8 patients.3, 4, 5, 6, 7, 8 This report shows a rare presentation of an SCN on the vermillion portion of the upper lip, along with its dermoscopic features.
Case report
A 50-year-old African American male was referred for evaluation of an asymptomatic solitary papule on the vermillion of the upper lip. The lesion had been present for 1 year. There was slow, steady growth at first, but no changes in size or appearance during the preceding 3 months. The patient denied any history of trauma to the upper lip or any color change, pain, tenderness, ulceration, or bleeding associated with the lesion. Examination showed a yellowish 3 mm × 3 mm smooth-surfaced papule of the upper lip vermillion, inferior to the vermillion border but superior to the wet-dry line. The lesion felt soft, somewhat rubbery, and freely moveable on palpation. Polarized dermoscopy revealed a dome-shaped smooth-surfaced papule with a yellow structureless background and overlying fingerprint-like pattern of surface pigmentation. No vascular or other structures were seen, and no surface scaling or ulcerations were present (Fig 1, A and B). The lesion was excised and sent for microscopic examination. The microscopic diagnosis was solitary encapsulated neuroma (Fig 2, A and B).
Fig 1.
Contact polarized dermoscopy of the yellow papule just inferior to the vermillion border of the upper lip. A, Straight-on view showing a dome-shaped papule with a yellow structureless background and overlying fingerprint-like pattern of superficial pigmentation without vascular structures. B, Lateral view (wobble sign on contact) showing a smooth translucent overlying epithelial surface.
Fig 2.
Microscopic features of the solitary circumscribed neuroma. A, Photomicrograph of hematoxylin and eosin stained (100× magnification) section shows a well-circumscribed benign spindle cells proliferation with focal palisading within a loose collagenous stroma, surrounded by a thin and incomplete fibrous capsule. B, Photomicrograph (100× magnification) reveals diffuse positivity of the lesional Schwann cells for S100 protein. There is no evidence of cytologic atypia, and mitotic figures are inconspicuous.
Discussion
SCNs of the skin have been described as clinical and dermoscopic mimickers of basal cell carcinomas due to their presentation as semitranslucent papules with arborizing vessels seen on dermoscopy.3,5,7,8 The 8 previously reported cases of singular SCNs with dermoscopic evaluation were all facial or neck skin lesions.3, 4, 5, 6, 7, 8 All except for one showed the presence of vasculature, a papule on the neck that showed a homogenous white structureless patch without any noticeable vessels.6 The dermoscopic features of SCNs reported in the literature are summarized in Table I.
Table I.
Summary of dermoscopic features of solitary circumscribed neuromas reported in the literature
| Study | Case | Location | Dermoscopic features |
|---|---|---|---|
| 2024, Konisky et al3 | 50 y/o, female | Cheek (skin) | Arborizing vessels, skin-colored |
| 56 y/o, female | Cheek (skin) | Arborizing vessels, skin-colored | |
| 2020, Ramirez-Bellver et al4 | 30 y/o, female | Cheek (skin) | Polymorphous vessels, whitish nodule, reddish background, focal erosion |
| 2018, Fernandez-Crehuet et al5 | 66 y/o, female | Lower lip (skin) | Arborizing vessels, pinkish background, central white spot, peripheral yellowish halo |
| 2017, Moyano et al6 | 52 y/o, male | Cheek (skin) | Ivory-white patch |
| 2015, Fernandez-Crehuet et al7 | 43 y/o, female | Neck (skin) | Arborizing vessels, pink background, peripheral yellowish halo |
| 49 y/o, female | Cheek (skin) | Arborizing vessels, pink background | |
| 2015, Riserva et al8 | 42 y/o, male | Upper lip (skin) | Arborizing vessels, pink background |
y/o, Year-old.
The lesion described in this report using polarized dermoscopy showed a dome-shaped papule with a yellow structureless background and an overlying fingerprint-like pattern of superficial pigmentation. Vascular structures, as found in SCNs of the skin, were not seen. The fingerprint-like pattern of surface pigmentation corresponds to distortion of native vermillion pigmentation by the raised lesion rather than pigmentation arising from the lesion itself.
This pattern and distribution of overlying pigmented structures (fingerprint-like lines) may contribute to the dermoscopic appearance of subepithelial papular lesions at the vermillion of the lips. Other subepithelial reactive or neoplastic nodules found at the vermillion, such as fibromas, schwannomas, or lesions arising from minor salivary or ectopic sebaceous glands, may show the same dermoscopic appearance as seen in the SCN reported in this case. Few studies have evaluated the native pigmented structures of the lip vermillion in the absence of pathology.9,10 The presence of such structures may be more pronounced in skin of color, as in this case, creating a different dermoscopic appearance compared to lighter skin types.
In conclusion, although the dermoscopic appearance described in this report may not be specific to SCNs at the vermilion, arborizing vessels, as found in SCNs of the skin, were not seen. It is possible that the overlying fingerprint-like lines of physiologic pigmentation impeded their detection. Such a pattern of overlying pigmentation may be more pronounced in skin of color, creating a particular dermoscopic appearance. Alternatively, the anatomical characteristics of the submucosal microvasculature at the vermillion are such that telangiectatic vessels are not formed as a result of this benign pathologic process.
Conflicts of interest
None disclosed.
Acknowledgments
The authors acknowledge Yve Huttenbach, MD, and the Departments of Pathology of Baylor College Medicine and Ben Taub Hospital for producing the histopathologic images.
Footnotes
Funding sources: None.
Patient consent: The authors obtained written consent from patients for their photographs and medical information to be published in print and online and with the understanding that this information may be publicly available. Patient consent forms were not provided to the journal but are retained by the authors.
IRB approval status: Not applicable.
References
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