Other Tests
To date, dermoscopic findings have only been reported in two cases. One report describes a homogeneous light-yellowish core with a white scaly collar reflective of epidermal acanthosis, hyperkeratosis, and dense collagen fibers, which was seen histologically. In addition, the authors also describe red spherical vessels surrounding the entire lesion. The other report revealed the presence of numerous clumps of homogenous red lacunae divided by a white meshwork-like septal wall, along with telangiectasia in the adjacent skin. The latter authors attributed the white mesh-like network to the marked hyperkeratosis overlying irregular elongated rete ridges seen on histological examination. [23]
Histologic Findings
The overall architecture of an acquired digital fibrokeratoma is a small, well-circumscribed, dome-shaped or narrow elongated papule. The stratum corneum is typically hyperkeratotic, which tends to be most pronounced toward the summit of the lesion. The epidermis can be acanthotic, with elongation of the rete ridges or can be slightly attenuated.
The dermal core of an acquired digital fibrokeratoma displays one of three histological patterns, which were originally described by Bart et al [1] and further characterized by Kint et al. [24] Type I acquired digital fibrokeratoma is the most common type and consists of a dermal core composed of thick, closely intertwined collagen bundles that are often oriented along the vertical axis of the lesion. Between the collagen bundles are numerous capillaries, varying numbers of fibroblasts, and thin elastic fibers. Type II lesions are less common, and histologically resemble type I lesions, but in addition have a significantly increased number of fibroblasts arranged in fascicles and markedly reduced numbers of elastic fibers. Type III acquired digital fibrokeratoma is the least common type and consists of a dermal core that is poorly cellular and edematous with a reduced number of elastic fibers.
Domed-shaped papule with overlying hyperkeratosis. The dermal core is composed of increased collagen bundles and blood vessels oriented along the vertical axis of the lesion.
Close up showing the increased collagen bundles and blood vessels oriented along the vertical axis of the lesion.
A different acquired digital fibrokeratoma showing similar findings of a domed-shaped lesion with a vertically aligned fibrovascular core.
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Clinical picture of a pedunculated acquire digital fibrokeratoma.
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Flat-topped, skin-colored acquired digital fibrokeratoma in an acral location.
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Slightly raised skin encircling the base of an acquired digital fibrokeratoma, creating a moat.
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Domed-shaped papule with overlying hyperkeratosis. The dermal core is composed of increased collagen bundles and blood vessels oriented along the vertical axis of the lesion.
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Close up showing the increased collagen bundles and blood vessels oriented along the vertical axis of the lesion.
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A different acquired digital fibrokeratoma showing similar findings of a domed-shaped lesion with a vertically aligned fibrovascular core.
