Fibrokeratome acquired digital D23.L

Bart et al. 1968

Benign adult exophytic protuberance occurring on the fingers, growing very slowly and not regressing spontaneously. The growth starts spontaneously. Initially, a small, barely pinhead-sized, painless usually unnoticed, flatly protuberant, somewhat more keratinized nodule is found. The growth takes place over years. There is no tendency to regression.

The pathophysiology of acquired digital fibrokeratoma is unknown. Histologically, the tumor consists of denser fibers than normal skin and contains more fibroblasts and coarser elastic fibers. This leads to the assumption that it is a fibrocytic neoplasm. It has been reported that factor Xllla, which is present in fibrovascular tumors, has also been found in digital fibrokeratoma (Nemeth AJ et al 1989). In addition, collagen synthesis may be regulated by factor Xllla-positive dermal dendrocytes, which are more abundant in digital fibrokerfatoma. Therefore, factor Xllla may play a predominant role in the fibroblastic response.

Documented cases of acquired digital fibrokeratoma occur in patients of all ethnicities. Reports can be found in the German, Polish, Japanese, French, and Indian literature. Males appear to be more commonly affected than females, and the age range is from 12 to 70 years.

Occurring mainly on the fingers. Less frequently, the toes are affected (dorsal, medial or lateral side near the joint or surrounding the nail).

Fibrokeratoma has also been described on the lower lip, nose, elbow, in the area in front of the patellar tendons and in the periungual tissue (Tabka M 2023) .

Broad-based, solitary, hemispherical or pastille-shaped solid nodule (nodule) covered by skin free of papillary ridges and usually hyperkeratotic at the tip. Usually asymptomatic; occasionally there is tenderness, especially when occurring on the toes (due to pressure from footwear). The size of the lesion is usually less than 1 cm, but there are cases larger than 1 cm.

Fibroma with acanthotic spreading, orthohyperkeratotic epidermis, with thick collagen bundles oriented along the vertical axis in the dermis. The dermal core of a fibrokeratoma exhibits one of three histologic variants characterized by Kint et al (Kint A et al 1985):

Type I is the most common variant. It presents as a dome-shaped lesion and consists of a dermal core of thick, densely packed collagen bundles with fine elastic fibers (Kint A et al. 1985)

Type II is a predominantly high and hyperkeratotic nodule . It has more fibroblasts arranged in the cutis than the first type with fewer elastic fibers (Kint A et al 1985).

Type III is the least common variety. It is a flat to dome-shaped lesion with a cell-poor dermal core, edematous structures, and absent elastic fibers.

Rudimentary polydactyly (digitus supranumularis, occurs mainly on the ulnar side of the 5th finger);

True knuckle pads and false knuckle pads;

Koenen's tumor

Verrucae vulgares

Cornu cutaneum: this refers to an exophytic and hyperkeratotic proliferation containing a keratin column. Histological examination may indicate a premalignant or malignant process.

Cutaneous neurofibromas: these may have a clinical resemblance. However, they are soft and polyp-like. Histologic examination reveals loosely distributed spindle cells, wavy collagenous strands, and a myxoid matrix.

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There are reports of various therapeutic options, including cryotherapy, curettage, and cauterization.

Sufficiently deep excision without a substantial safety margin is recommended (Tabka M 2023).

Recurrences are possible. In these cases, radical surgical intervention gfls. with occlusive flapoplasty is recommended.

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3. Cogrel O (2016) Exérèse tangentielle d'un fibrokératome digital acquis de la matrice proximale associé à une exostose sous-unguéale du pouce. Ann Dermatol Venereol 143:407-408.
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7. Nemeth AJ et al (1989) Factor XIIIa is expressed by fibroblasts in fibrovascular tumors. J Cutan Pathol. 16:266-271.
8. Reye RD (1965) Recurrent digital fibrous tumors of childhood. Arch Pathol 80: 228-231
9. Tabka M (2023) Acquired digital fibrokeratoma. 2022 May 1. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. PMID: 31424730.
10. Wollina U et al (1990) The acquired acral fibrokeratoma. Dermatologist 41: 158-160