Dynamic Motion Dermoscopy of Anetodermic Pilomatricoma

Pilomatricoma is a benign adnexal tumour arising from hair matrix cells, typically presents as a solitary, firm, well‐defined painless nodule. It tends to involve the head, neck, and upper extremities, while the trunk and lower limbs are less frequently affected. Anetodermic pilomatricoma, also referred to as pseudobullous or keloid‐like pilomatricoma, is a rare variant accounting for approximately 2% of cases. It is characterized by overlying atrophic, wrinkled skin resulting from focal loss of dermal elastic tissue, creating a distinctive bullous‐like appearance that differentiates it from the classic presentation [1].

Clinical and dermoscopic features of both pilomatricoma and its anetodermic variant have been described previously [2, 3, 4]. The aim of this report is to present four cases of anetodermic pilomatricoma, with particular emphasis on dynamic motion dermoscopy, which highlights diagnostic features not evident on static evaluation.

Four patients (2 males, 2 females; median age 19.5 years) presented with rapidly evolving nodules (median duration 4.5 months) located on the neck (n = 2), axilla (n = 1), and knee (n = 1) (Figure 1). Static and dynamic motion dermoscopy was performed using a DermLite DL4 dermatoscope (3Gen, San Juan Capistrano, CA, USA).

FIGURE 1.

Clinical and dermoscopic features of anetodermic pilomatricoma. Left column (a–d): clinical photographs; right column (a′–d′): corresponding dermoscopic images. Cases 1–3 (a–c′) show the classic dermoscopic features: central structureless yellowish‐white areas, a prominent bluish peripheral rim, and fine peripheral telangiectatic vessels. Case 4 (d–d′) presented with a less characteristic clinical and dermoscopic pattern, showing predominantly the bluish rim and peripheral erythema without a well‐defined central yellowish‐white zone, likely reflecting early‐stage lesion evolution with limited calcification. Dermoscopy was performed using a DermLite DL4 dermatoscope (3Gen, San Juan Capistrano, CA, USA).

All lesions demonstrated characteristic anetodermic changes: erythematous protuberant lesions with overlying atrophic, wrinkled, translucent skin and underlying firm nodules. The diagnosis was confirmed histopathologically in all cases. Histopathological examination in all cases revealed islands of basaloid and shadow (ghost) cells with dystrophic calcification and a thinned epidermis consistent with the anetodermic variant.

Static dermoscopy revealed consistent features across all cases: central structureless yellow‐white areas, a prominent bluish peripheral rim, peripheral reddish areas, and fine linear telangiectatic vessels (Figure 1).

Dynamic motion dermoscopy from case 1 (Figure 1a–a′) revealed additional findings not appreciable on static images (Figure 2; Video S1):

1. The ‘translucent sign’: Real‐time examination demonstrated variable translucency of the thinned dermis, permitting direct visualization of deeper tumour architecture. The degree of translucency fluctuated with both illumination angle and application of vertical pressure (Figure 2a,b), progressively revealing internal characteristics that are unlikely to be captured on static images. In particular, the central structureless yellowish‐white area—corresponding to the calcified tumour core—and the intensity of the bluish peripheral rim may be variably apparent on static images; dynamic examination allowed these features to be fully appreciated.

2. Three‐dimensional depth perception: Lateral horizontal pressure applied with the dermatoscope induced visible wrinkling and folding of the atrophic overlying skin (Figure 2c,d), demonstrating marked loss of dermal elasticity and structural integrity. The bluish rim appeared to ‘float’ over the deeper tumour mass, emphasizing the spatial separation between the atrophic superficial dermis and the underlying firm neoplasm.

FIGURE 2.

Dynamic motion dermoscopy of anetodermic pilomatricoma (Case 1). (a, b) Dermoscopic images showing central white areas, bluish rim, and translucent overlying skin. The degree of translucency fluctuated with both illumination angle and applied vertical pressure. (c, d) Lateral pressure towards the left and right respectively, causing visible wrinkling of atrophic skin. Dynamic dermoscopy was performed using a DermLite DL4 dermatoscope (3Gen, San Juan Capistrano, CA, USA).

Dermoscopic motion assessment has been previously described as a useful adjunctive technique for intradermal nevi. Nazir et al. introduced the ‘wobble sign’, in which horizontal pressure applied with the dermatoscope causes the lesion to roll or wobble, reflecting its dermal origin and assisting in the differentiation from cutaneous malignancies [5].

Similarly, our video documentation illustrates how motion‐based manipulation during real‐time dermoscopic examination of anetodermic pilomatricoma can reveal diagnostic relevant features that may not be evident on static evaluation, particularly the translucent quality and independent mobility of the overlying atrophic skin relative to the deeper tumour mass.

In our cases, a prominent peripheral bluish rim was consistently observed, in line with the findings reported by Dev et al. In contrast, other authors have described a blue–grey central zone with an erythematous periphery and a whitish‐blue veil with chrysalis‐like structures [2, 3, 4]. Such variability may reflect differences in lesion evolution, calcification extent, tumour depth, or as suggested by our dynamic video documentation, variations in examination angle and illumination. The ‘translucent sign’ highlights that dermoscopic appearance may actively change during real‐time examination, potentially reconciling previously reported variations by capturing the complete morphologic spectrum rather than a single static moment.

The ‘translucent sign’ appears to be a distinctive feature of anetodermic pilomatricoma and may aid in distinguishing it from common clinical mimickers such as keloid scars, dermatofibroma, epidermoid cysts, and vascular lesions.

Our video documentation suggests that motion‐based manipulation during real‐time dermoscopy can highlight diagnostically relevant findings that are not consistently captured on static imaging alone. In particular, the ‘translucent sign’ may represent a useful dermoscopic marker of anetodermic pilomatricoma and could improve diagnostic confidence when evaluating clinically similar lesions. Further studies in larger cohorts are warranted to determine its reproducibility and diagnostic performance.

Author Contributions

All authors have contributed significantly to the preparation of this manuscript and have approved the final version.

Funding

The authors have nothing to report.

Conflicts of Interest

The authors declare no conflicts of interest.

Supporting information

Video S1: Supporting Information.

Data Availability Statement

The authors have nothing to report.